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postgres/src/backend/optimizer/path/allpaths.c
David Rowley eb7d043c9b Fix incorrect logic for determining safe WindowAgg run conditions 
The logic added in 9d9c02ccd to determine when a qual can be used as a
WindowClause run condition failed to correctly check for subqueries in the
qual.  This was being done correctly for normal subquery qual pushdowns,
it's just that 9d9c02ccd failed to follow the lead on that.

This also fixes various other cases where transforming the qual into a
WindowClause run condition in the subquery should have been disallowed.

Bug: #17826
Reported-by: Anban Company
Discussion: https://postgr.es/m/17826-7d8750952f19a5f5@postgresql.org
Backpatch-through: 15, where 9d9c02ccd was introduced.
2023-03-17 15:49:53 +13:00

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/*-------------------------------------------------------------------------
*
* allpaths.c
* Routines to find possible search paths for processing a query
*
* Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/optimizer/path/allpaths.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include <limits.h>
#include <math.h>
#include "access/sysattr.h"
#include "access/tsmapi.h"
#include "catalog/pg_class.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "foreign/fdwapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "nodes/supportnodes.h"
#ifdef OPTIMIZER_DEBUG
#include "nodes/print.h"
#endif
#include "optimizer/appendinfo.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/geqo.h"
#include "optimizer/inherit.h"
#include "optimizer/optimizer.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/plancat.h"
#include "optimizer/planner.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/tlist.h"
#include "parser/parse_clause.h"
#include "parser/parsetree.h"
#include "partitioning/partbounds.h"
#include "partitioning/partprune.h"
#include "port/pg_bitutils.h"
#include "rewrite/rewriteManip.h"
#include "utils/lsyscache.h"
/* Bitmask flags for pushdown_safety_info.unsafeFlags */
#define UNSAFE_HAS_VOLATILE_FUNC (1 << 0)
#define UNSAFE_HAS_SET_FUNC (1 << 1)
#define UNSAFE_NOTIN_DISTINCTON_CLAUSE (1 << 2)
#define UNSAFE_NOTIN_PARTITIONBY_CLAUSE (1 << 3)
#define UNSAFE_TYPE_MISMATCH (1 << 4)
/* results of subquery_is_pushdown_safe */
typedef struct pushdown_safety_info
{
unsigned char *unsafeFlags; /* bitmask of reasons why this target list
* column is unsafe for qual pushdown, or 0 if
* no reason. */
bool unsafeVolatile; /* don't push down volatile quals */
bool unsafeLeaky; /* don't push down leaky quals */
} pushdown_safety_info;
/* Return type for qual_is_pushdown_safe */
typedef enum pushdown_safe_type
{
PUSHDOWN_UNSAFE, /* unsafe to push qual into subquery */
PUSHDOWN_SAFE, /* safe to push qual into subquery */
PUSHDOWN_WINDOWCLAUSE_RUNCOND /* unsafe, but may work as WindowClause
* run condition */
} pushdown_safe_type;
/* These parameters are set by GUC */
bool enable_geqo = false; /* just in case GUC doesn't set it */
int geqo_threshold;
int min_parallel_table_scan_size;
int min_parallel_index_scan_size;
/* Hook for plugins to get control in set_rel_pathlist() */
set_rel_pathlist_hook_type set_rel_pathlist_hook = NULL;
/* Hook for plugins to replace standard_join_search() */
join_search_hook_type join_search_hook = NULL;
static void set_base_rel_consider_startup(PlannerInfo *root);
static void set_base_rel_sizes(PlannerInfo *root);
static void set_base_rel_pathlists(PlannerInfo *root);
static void set_rel_size(PlannerInfo *root, RelOptInfo *rel,
Index rti, RangeTblEntry *rte);
static void set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
Index rti, RangeTblEntry *rte);
static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel);
static void set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
Index rti, RangeTblEntry *rte);
static void set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
Index rti, RangeTblEntry *rte);
static void generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel,
List *live_childrels,
List *all_child_pathkeys);
static Path *get_cheapest_parameterized_child_path(PlannerInfo *root,
RelOptInfo *rel,
Relids required_outer);
static void accumulate_append_subpath(Path *path,
List **subpaths,
List **special_subpaths);
static Path *get_singleton_append_subpath(Path *path);
static void set_dummy_rel_pathlist(RelOptInfo *rel);
static void set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
Index rti, RangeTblEntry *rte);
static void set_function_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_values_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_tablefunc_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_namedtuplestore_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_result_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static void set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte);
static RelOptInfo *make_rel_from_joinlist(PlannerInfo *root, List *joinlist);
static bool subquery_is_pushdown_safe(Query *subquery, Query *topquery,
pushdown_safety_info *safetyInfo);
static bool recurse_pushdown_safe(Node *setOp, Query *topquery,
pushdown_safety_info *safetyInfo);
static void check_output_expressions(Query *subquery,
pushdown_safety_info *safetyInfo);
static void compare_tlist_datatypes(List *tlist, List *colTypes,
pushdown_safety_info *safetyInfo);
static bool targetIsInAllPartitionLists(TargetEntry *tle, Query *query);
static pushdown_safe_type qual_is_pushdown_safe(Query *subquery, Index rti,
RestrictInfo *rinfo,
pushdown_safety_info *safetyInfo);
static void subquery_push_qual(Query *subquery,
RangeTblEntry *rte, Index rti, Node *qual);
static void recurse_push_qual(Node *setOp, Query *topquery,
RangeTblEntry *rte, Index rti, Node *qual);
static void remove_unused_subquery_outputs(Query *subquery, RelOptInfo *rel,
Bitmapset *extra_used_attrs);
/*
* make_one_rel
* Finds all possible access paths for executing a query, returning a
* single rel that represents the join of all base rels in the query.
*/
RelOptInfo *
make_one_rel(PlannerInfo *root, List *joinlist)
{
RelOptInfo *rel;
Index rti;
double total_pages;
/* Mark base rels as to whether we care about fast-start plans */
set_base_rel_consider_startup(root);
/*
* Compute size estimates and consider_parallel flags for each base rel.
*/
set_base_rel_sizes(root);
/*
* We should now have size estimates for every actual table involved in
* the query, and we also know which if any have been deleted from the
* query by join removal, pruned by partition pruning, or eliminated by
* constraint exclusion. So we can now compute total_table_pages.
*
* Note that appendrels are not double-counted here, even though we don't
* bother to distinguish RelOptInfos for appendrel parents, because the
* parents will have pages = 0.
*
* XXX if a table is self-joined, we will count it once per appearance,
* which perhaps is the wrong thing ... but that's not completely clear,
* and detecting self-joins here is difficult, so ignore it for now.
*/
total_pages = 0;
for (rti = 1; rti < root->simple_rel_array_size; rti++)
{
RelOptInfo *brel = root->simple_rel_array[rti];
/* there may be empty slots corresponding to non-baserel RTEs */
if (brel == NULL)
continue;
Assert(brel->relid == rti); /* sanity check on array */
if (IS_DUMMY_REL(brel))
continue;
if (IS_SIMPLE_REL(brel))
total_pages += (double) brel->pages;
}
root->total_table_pages = total_pages;
/*
* Generate access paths for each base rel.
*/
set_base_rel_pathlists(root);
/*
* Generate access paths for the entire join tree.
*/
rel = make_rel_from_joinlist(root, joinlist);
/*
* The result should join all and only the query's base + outer-join rels.
*/
Assert(bms_equal(rel->relids, root->all_query_rels));
return rel;
}
/*
* set_base_rel_consider_startup
* Set the consider_[param_]startup flags for each base-relation entry.
*
* For the moment, we only deal with consider_param_startup here; because the
* logic for consider_startup is pretty trivial and is the same for every base
* relation, we just let build_simple_rel() initialize that flag correctly to
* start with. If that logic ever gets more complicated it would probably
* be better to move it here.
*/
static void
set_base_rel_consider_startup(PlannerInfo *root)
{
/*
* Since parameterized paths can only be used on the inside of a nestloop
* join plan, there is usually little value in considering fast-start
* plans for them. However, for relations that are on the RHS of a SEMI
* or ANTI join, a fast-start plan can be useful because we're only going
* to care about fetching one tuple anyway.
*
* To minimize growth of planning time, we currently restrict this to
* cases where the RHS is a single base relation, not a join; there is no
* provision for consider_param_startup to get set at all on joinrels.
* Also we don't worry about appendrels. costsize.c's costing rules for
* nestloop semi/antijoins don't consider such cases either.
*/
ListCell *lc;
foreach(lc, root->join_info_list)
{
SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
int varno;
if ((sjinfo->jointype == JOIN_SEMI || sjinfo->jointype == JOIN_ANTI) &&
bms_get_singleton_member(sjinfo->syn_righthand, &varno))
{
RelOptInfo *rel = find_base_rel(root, varno);
rel->consider_param_startup = true;
}
}
}
/*
* set_base_rel_sizes
* Set the size estimates (rows and widths) for each base-relation entry.
* Also determine whether to consider parallel paths for base relations.
*
* We do this in a separate pass over the base rels so that rowcount
* estimates are available for parameterized path generation, and also so
* that each rel's consider_parallel flag is set correctly before we begin to
* generate paths.
*/
static void
set_base_rel_sizes(PlannerInfo *root)
{
Index rti;
for (rti = 1; rti < root->simple_rel_array_size; rti++)
{
RelOptInfo *rel = root->simple_rel_array[rti];
RangeTblEntry *rte;
/* there may be empty slots corresponding to non-baserel RTEs */
if (rel == NULL)
continue;
Assert(rel->relid == rti); /* sanity check on array */
/* ignore RTEs that are "other rels" */
if (rel->reloptkind != RELOPT_BASEREL)
continue;
rte = root->simple_rte_array[rti];
/*
* If parallelism is allowable for this query in general, see whether
* it's allowable for this rel in particular. We have to do this
* before set_rel_size(), because (a) if this rel is an inheritance
* parent, set_append_rel_size() will use and perhaps change the rel's
* consider_parallel flag, and (b) for some RTE types, set_rel_size()
* goes ahead and makes paths immediately.
*/
if (root->glob->parallelModeOK)
set_rel_consider_parallel(root, rel, rte);
set_rel_size(root, rel, rti, rte);
}
}
/*
* set_base_rel_pathlists
* Finds all paths available for scanning each base-relation entry.
* Sequential scan and any available indices are considered.
* Each useful path is attached to its relation's 'pathlist' field.
*/
static void
set_base_rel_pathlists(PlannerInfo *root)
{
Index rti;
for (rti = 1; rti < root->simple_rel_array_size; rti++)
{
RelOptInfo *rel = root->simple_rel_array[rti];
/* there may be empty slots corresponding to non-baserel RTEs */
if (rel == NULL)
continue;
Assert(rel->relid == rti); /* sanity check on array */
/* ignore RTEs that are "other rels" */
if (rel->reloptkind != RELOPT_BASEREL)
continue;
set_rel_pathlist(root, rel, rti, root->simple_rte_array[rti]);
}
}
/*
* set_rel_size
* Set size estimates for a base relation
*/
static void
set_rel_size(PlannerInfo *root, RelOptInfo *rel,
Index rti, RangeTblEntry *rte)
{
if (rel->reloptkind == RELOPT_BASEREL &&
relation_excluded_by_constraints(root, rel, rte))
{
/*
* We proved we don't need to scan the rel via constraint exclusion,
* so set up a single dummy path for it. Here we only check this for
* regular baserels; if it's an otherrel, CE was already checked in
* set_append_rel_size().
*
* In this case, we go ahead and set up the relation's path right away
* instead of leaving it for set_rel_pathlist to do. This is because
* we don't have a convention for marking a rel as dummy except by
* assigning a dummy path to it.
*/
set_dummy_rel_pathlist(rel);
}
else if (rte->inh)
{
/* It's an "append relation", process accordingly */
set_append_rel_size(root, rel, rti, rte);
}
else
{
switch (rel->rtekind)
{
case RTE_RELATION:
if (rte->relkind == RELKIND_FOREIGN_TABLE)
{
/* Foreign table */
set_foreign_size(root, rel, rte);
}
else if (rte->relkind == RELKIND_PARTITIONED_TABLE)
{
/*
* We could get here if asked to scan a partitioned table
* with ONLY. In that case we shouldn't scan any of the
* partitions, so mark it as a dummy rel.
*/
set_dummy_rel_pathlist(rel);
}
else if (rte->tablesample != NULL)
{
/* Sampled relation */
set_tablesample_rel_size(root, rel, rte);
}
else
{
/* Plain relation */
set_plain_rel_size(root, rel, rte);
}
break;
case RTE_SUBQUERY:
/*
* Subqueries don't support making a choice between
* parameterized and unparameterized paths, so just go ahead
* and build their paths immediately.
*/
set_subquery_pathlist(root, rel, rti, rte);
break;
case RTE_FUNCTION:
set_function_size_estimates(root, rel);
break;
case RTE_TABLEFUNC:
set_tablefunc_size_estimates(root, rel);
break;
case RTE_VALUES:
set_values_size_estimates(root, rel);
break;
case RTE_CTE:
/*
* CTEs don't support making a choice between parameterized
* and unparameterized paths, so just go ahead and build their
* paths immediately.
*/
if (rte->self_reference)
set_worktable_pathlist(root, rel, rte);
else
set_cte_pathlist(root, rel, rte);
break;
case RTE_NAMEDTUPLESTORE:
/* Might as well just build the path immediately */
set_namedtuplestore_pathlist(root, rel, rte);
break;
case RTE_RESULT:
/* Might as well just build the path immediately */
set_result_pathlist(root, rel, rte);
break;
default:
elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
break;
}
}
/*
* We insist that all non-dummy rels have a nonzero rowcount estimate.
*/
Assert(rel->rows > 0 || IS_DUMMY_REL(rel));
}
/*
* set_rel_pathlist
* Build access paths for a base relation
*/
static void
set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
Index rti, RangeTblEntry *rte)
{
if (IS_DUMMY_REL(rel))
{
/* We already proved the relation empty, so nothing more to do */
}
else if (rte->inh)
{
/* It's an "append relation", process accordingly */
set_append_rel_pathlist(root, rel, rti, rte);
}
else
{
switch (rel->rtekind)
{
case RTE_RELATION:
if (rte->relkind == RELKIND_FOREIGN_TABLE)
{
/* Foreign table */
set_foreign_pathlist(root, rel, rte);
}
else if (rte->tablesample != NULL)
{
/* Sampled relation */
set_tablesample_rel_pathlist(root, rel, rte);
}
else
{
/* Plain relation */
set_plain_rel_pathlist(root, rel, rte);
}
break;
case RTE_SUBQUERY:
/* Subquery --- fully handled during set_rel_size */
break;
case RTE_FUNCTION:
/* RangeFunction */
set_function_pathlist(root, rel, rte);
break;
case RTE_TABLEFUNC:
/* Table Function */
set_tablefunc_pathlist(root, rel, rte);
break;
case RTE_VALUES:
/* Values list */
set_values_pathlist(root, rel, rte);
break;
case RTE_CTE:
/* CTE reference --- fully handled during set_rel_size */
break;
case RTE_NAMEDTUPLESTORE:
/* tuplestore reference --- fully handled during set_rel_size */
break;
case RTE_RESULT:
/* simple Result --- fully handled during set_rel_size */
break;
default:
elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
break;
}
}
/*
* Allow a plugin to editorialize on the set of Paths for this base
* relation. It could add new paths (such as CustomPaths) by calling
* add_path(), or add_partial_path() if parallel aware. It could also
* delete or modify paths added by the core code.
*/
if (set_rel_pathlist_hook)
(*set_rel_pathlist_hook) (root, rel, rti, rte);
/*
* If this is a baserel, we should normally consider gathering any partial
* paths we may have created for it. We have to do this after calling the
* set_rel_pathlist_hook, else it cannot add partial paths to be included
* here.
*
* However, if this is an inheritance child, skip it. Otherwise, we could
* end up with a very large number of gather nodes, each trying to grab
* its own pool of workers. Instead, we'll consider gathering partial
* paths for the parent appendrel.
*
* Also, if this is the topmost scan/join rel, we postpone gathering until
* the final scan/join targetlist is available (see grouping_planner).
*/
if (rel->reloptkind == RELOPT_BASEREL &&
!bms_equal(rel->relids, root->all_query_rels))
generate_useful_gather_paths(root, rel, false);
/* Now find the cheapest of the paths for this rel */
set_cheapest(rel);
#ifdef OPTIMIZER_DEBUG
debug_print_rel(root, rel);
#endif
}
/*
* set_plain_rel_size
* Set size estimates for a plain relation (no subquery, no inheritance)
*/
static void
set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
/*
* Test any partial indexes of rel for applicability. We must do this
* first since partial unique indexes can affect size estimates.
*/
check_index_predicates(root, rel);
/* Mark rel with estimated output rows, width, etc */
set_baserel_size_estimates(root, rel);
}
/*
* If this relation could possibly be scanned from within a worker, then set
* its consider_parallel flag.
*/
static void
set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte)
{
/*
* The flag has previously been initialized to false, so we can just
* return if it becomes clear that we can't safely set it.
*/
Assert(!rel->consider_parallel);
/* Don't call this if parallelism is disallowed for the entire query. */
Assert(root->glob->parallelModeOK);
/* This should only be called for baserels and appendrel children. */
Assert(IS_SIMPLE_REL(rel));
/* Assorted checks based on rtekind. */
switch (rte->rtekind)
{
case RTE_RELATION:
/*
* Currently, parallel workers can't access the leader's temporary
* tables. We could possibly relax this if we wrote all of its
* local buffers at the start of the query and made no changes
* thereafter (maybe we could allow hint bit changes), and if we
* taught the workers to read them. Writing a large number of
* temporary buffers could be expensive, though, and we don't have
* the rest of the necessary infrastructure right now anyway. So
* for now, bail out if we see a temporary table.
*/
if (get_rel_persistence(rte->relid) == RELPERSISTENCE_TEMP)
return;
/*
* Table sampling can be pushed down to workers if the sample
* function and its arguments are safe.
*/
if (rte->tablesample != NULL)
{
char proparallel = func_parallel(rte->tablesample->tsmhandler);
if (proparallel != PROPARALLEL_SAFE)
return;
if (!is_parallel_safe(root, (Node *) rte->tablesample->args))
return;
}
/*
* Ask FDWs whether they can support performing a ForeignScan
* within a worker. Most often, the answer will be no. For
* example, if the nature of the FDW is such that it opens a TCP
* connection with a remote server, each parallel worker would end
* up with a separate connection, and these connections might not
* be appropriately coordinated between workers and the leader.
*/
if (rte->relkind == RELKIND_FOREIGN_TABLE)
{
Assert(rel->fdwroutine);
if (!rel->fdwroutine->IsForeignScanParallelSafe)
return;
if (!rel->fdwroutine->IsForeignScanParallelSafe(root, rel, rte))
return;
}
/*
* There are additional considerations for appendrels, which we'll
* deal with in set_append_rel_size and set_append_rel_pathlist.
* For now, just set consider_parallel based on the rel's own
* quals and targetlist.
*/
break;
case RTE_SUBQUERY:
/*
* There's no intrinsic problem with scanning a subquery-in-FROM
* (as distinct from a SubPlan or InitPlan) in a parallel worker.
* If the subquery doesn't happen to have any parallel-safe paths,
* then flagging it as consider_parallel won't change anything,
* but that's true for plain tables, too. We must set
* consider_parallel based on the rel's own quals and targetlist,
* so that if a subquery path is parallel-safe but the quals and
* projection we're sticking onto it are not, we correctly mark
* the SubqueryScanPath as not parallel-safe. (Note that
* set_subquery_pathlist() might push some of these quals down
* into the subquery itself, but that doesn't change anything.)
*
* We can't push sub-select containing LIMIT/OFFSET to workers as
* there is no guarantee that the row order will be fully
* deterministic, and applying LIMIT/OFFSET will lead to
* inconsistent results at the top-level. (In some cases, where
* the result is ordered, we could relax this restriction. But it
* doesn't currently seem worth expending extra effort to do so.)
*/
{
Query *subquery = castNode(Query, rte->subquery);
if (limit_needed(subquery))
return;
}
break;
case RTE_JOIN:
/* Shouldn't happen; we're only considering baserels here. */
Assert(false);
return;
case RTE_FUNCTION:
/* Check for parallel-restricted functions. */
if (!is_parallel_safe(root, (Node *) rte->functions))
return;
break;
case RTE_TABLEFUNC:
/* not parallel safe */
return;
case RTE_VALUES:
/* Check for parallel-restricted functions. */
if (!is_parallel_safe(root, (Node *) rte->values_lists))
return;
break;
case RTE_CTE:
/*
* CTE tuplestores aren't shared among parallel workers, so we
* force all CTE scans to happen in the leader. Also, populating
* the CTE would require executing a subplan that's not available
* in the worker, might be parallel-restricted, and must get
* executed only once.
*/
return;
case RTE_NAMEDTUPLESTORE:
/*
* tuplestore cannot be shared, at least without more
* infrastructure to support that.
*/
return;
case RTE_RESULT:
/* RESULT RTEs, in themselves, are no problem. */
break;
}
/*
* If there's anything in baserestrictinfo that's parallel-restricted, we
* give up on parallelizing access to this relation. We could consider
* instead postponing application of the restricted quals until we're
* above all the parallelism in the plan tree, but it's not clear that
* that would be a win in very many cases, and it might be tricky to make
* outer join clauses work correctly. It would likely break equivalence
* classes, too.
*/
if (!is_parallel_safe(root, (Node *) rel->baserestrictinfo))
return;
/*
* Likewise, if the relation's outputs are not parallel-safe, give up.
* (Usually, they're just Vars, but sometimes they're not.)
*/
if (!is_parallel_safe(root, (Node *) rel->reltarget->exprs))
return;
/* We have a winner. */
rel->consider_parallel = true;
}
/*
* set_plain_rel_pathlist
* Build access paths for a plain relation (no subquery, no inheritance)
*/
static void
set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
Relids required_outer;
/*
* We don't support pushing join clauses into the quals of a seqscan, but
* it could still have required parameterization due to LATERAL refs in
* its tlist.
*/
required_outer = rel->lateral_relids;
/* Consider sequential scan */
add_path(rel, create_seqscan_path(root, rel, required_outer, 0));
/* If appropriate, consider parallel sequential scan */
if (rel->consider_parallel && required_outer == NULL)
create_plain_partial_paths(root, rel);
/* Consider index scans */
create_index_paths(root, rel);
/* Consider TID scans */
create_tidscan_paths(root, rel);
}
/*
* create_plain_partial_paths
* Build partial access paths for parallel scan of a plain relation
*/
static void
create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel)
{
int parallel_workers;
parallel_workers = compute_parallel_worker(rel, rel->pages, -1,
max_parallel_workers_per_gather);
/* If any limit was set to zero, the user doesn't want a parallel scan. */
if (parallel_workers <= 0)
return;
/* Add an unordered partial path based on a parallel sequential scan. */
add_partial_path(rel, create_seqscan_path(root, rel, NULL, parallel_workers));
}
/*
* set_tablesample_rel_size
* Set size estimates for a sampled relation
*/
static void
set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
TableSampleClause *tsc = rte->tablesample;
TsmRoutine *tsm;
BlockNumber pages;
double tuples;
/*
* Test any partial indexes of rel for applicability. We must do this
* first since partial unique indexes can affect size estimates.
*/
check_index_predicates(root, rel);
/*
* Call the sampling method's estimation function to estimate the number
* of pages it will read and the number of tuples it will return. (Note:
* we assume the function returns sane values.)
*/
tsm = GetTsmRoutine(tsc->tsmhandler);
tsm->SampleScanGetSampleSize(root, rel, tsc->args,
&pages, &tuples);
/*
* For the moment, because we will only consider a SampleScan path for the
* rel, it's okay to just overwrite the pages and tuples estimates for the
* whole relation. If we ever consider multiple path types for sampled
* rels, we'll need more complication.
*/
rel->pages = pages;
rel->tuples = tuples;
/* Mark rel with estimated output rows, width, etc */
set_baserel_size_estimates(root, rel);
}
/*
* set_tablesample_rel_pathlist
* Build access paths for a sampled relation
*/
static void
set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
Relids required_outer;
Path *path;
/*
* We don't support pushing join clauses into the quals of a samplescan,
* but it could still have required parameterization due to LATERAL refs
* in its tlist or TABLESAMPLE arguments.
*/
required_outer = rel->lateral_relids;
/* Consider sampled scan */
path = create_samplescan_path(root, rel, required_outer);
/*
* If the sampling method does not support repeatable scans, we must avoid
* plans that would scan the rel multiple times. Ideally, we'd simply
* avoid putting the rel on the inside of a nestloop join; but adding such
* a consideration to the planner seems like a great deal of complication
* to support an uncommon usage of second-rate sampling methods. Instead,
* if there is a risk that the query might perform an unsafe join, just
* wrap the SampleScan in a Materialize node. We can check for joins by
* counting the membership of all_query_rels (note that this correctly
* counts inheritance trees as single rels). If we're inside a subquery,
* we can't easily check whether a join might occur in the outer query, so
* just assume one is possible.
*
* GetTsmRoutine is relatively expensive compared to the other tests here,
* so check repeatable_across_scans last, even though that's a bit odd.
*/
if ((root->query_level > 1 ||
bms_membership(root->all_query_rels) != BMS_SINGLETON) &&
!(GetTsmRoutine(rte->tablesample->tsmhandler)->repeatable_across_scans))
{
path = (Path *) create_material_path(rel, path);
}
add_path(rel, path);
/* For the moment, at least, there are no other paths to consider */
}
/*
* set_foreign_size
* Set size estimates for a foreign table RTE
*/
static void
set_foreign_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
/* Mark rel with estimated output rows, width, etc */
set_foreign_size_estimates(root, rel);
/* Let FDW adjust the size estimates, if it can */
rel->fdwroutine->GetForeignRelSize(root, rel, rte->relid);
/* ... but do not let it set the rows estimate to zero */
rel->rows = clamp_row_est(rel->rows);
/*
* Also, make sure rel->tuples is not insane relative to rel->rows.
* Notably, this ensures sanity if pg_class.reltuples contains -1 and the
* FDW doesn't do anything to replace that.
*/
rel->tuples = Max(rel->tuples, rel->rows);
}
/*
* set_foreign_pathlist
* Build access paths for a foreign table RTE
*/
static void
set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
/* Call the FDW's GetForeignPaths function to generate path(s) */
rel->fdwroutine->GetForeignPaths(root, rel, rte->relid);
}
/*
* set_append_rel_size
* Set size estimates for a simple "append relation"
*
* The passed-in rel and RTE represent the entire append relation. The
* relation's contents are computed by appending together the output of the
* individual member relations. Note that in the non-partitioned inheritance
* case, the first member relation is actually the same table as is mentioned
* in the parent RTE ... but it has a different RTE and RelOptInfo. This is
* a good thing because their outputs are not the same size.
*/
static void
set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
Index rti, RangeTblEntry *rte)
{
int parentRTindex = rti;
bool has_live_children;
double parent_rows;
double parent_size;
double *parent_attrsizes;
int nattrs;
ListCell *l;
/* Guard against stack overflow due to overly deep inheritance tree. */
check_stack_depth();
Assert(IS_SIMPLE_REL(rel));
/*
* If this is a partitioned baserel, set the consider_partitionwise_join
* flag; currently, we only consider partitionwise joins with the baserel
* if its targetlist doesn't contain a whole-row Var.
*/
if (enable_partitionwise_join &&
rel->reloptkind == RELOPT_BASEREL &&
rte->relkind == RELKIND_PARTITIONED_TABLE &&
bms_is_empty(rel->attr_needed[InvalidAttrNumber - rel->min_attr]))
rel->consider_partitionwise_join = true;
/*
* Initialize to compute size estimates for whole append relation.
*
* We handle width estimates by weighting the widths of different child
* rels proportionally to their number of rows. This is sensible because
* the use of width estimates is mainly to compute the total relation
* "footprint" if we have to sort or hash it. To do this, we sum the
* total equivalent size (in "double" arithmetic) and then divide by the
* total rowcount estimate. This is done separately for the total rel
* width and each attribute.
*
* Note: if you consider changing this logic, beware that child rels could
* have zero rows and/or width, if they were excluded by constraints.
*/
has_live_children = false;
parent_rows = 0;
parent_size = 0;
nattrs = rel->max_attr - rel->min_attr + 1;
parent_attrsizes = (double *) palloc0(nattrs * sizeof(double));
foreach(l, root->append_rel_list)
{
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
int childRTindex;
RangeTblEntry *childRTE;
RelOptInfo *childrel;
List *childrinfos;
ListCell *parentvars;
ListCell *childvars;
ListCell *lc;
/* append_rel_list contains all append rels; ignore others */
if (appinfo->parent_relid != parentRTindex)
continue;
childRTindex = appinfo->child_relid;
childRTE = root->simple_rte_array[childRTindex];
/*
* The child rel's RelOptInfo was already created during
* add_other_rels_to_query.
*/
childrel = find_base_rel(root, childRTindex);
Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);
/* We may have already proven the child to be dummy. */
if (IS_DUMMY_REL(childrel))
continue;
/*
* We have to copy the parent's targetlist and quals to the child,
* with appropriate substitution of variables. However, the
* baserestrictinfo quals were already copied/substituted when the
* child RelOptInfo was built. So we don't need any additional setup
* before applying constraint exclusion.
*/
if (relation_excluded_by_constraints(root, childrel, childRTE))
{
/*
* This child need not be scanned, so we can omit it from the
* appendrel.
*/
set_dummy_rel_pathlist(childrel);
continue;
}
/*
* Constraint exclusion failed, so copy the parent's join quals and
* targetlist to the child, with appropriate variable substitutions.
*
* We skip join quals that came from above outer joins that can null
* this rel, since they would be of no value while generating paths
* for the child. This saves some effort while processing the child
* rel, and it also avoids an implementation restriction in
* adjust_appendrel_attrs (it can't apply nullingrels to a non-Var).
*/
childrinfos = NIL;
foreach(lc, rel->joininfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
if (!bms_overlap(rinfo->clause_relids, rel->nulling_relids))
childrinfos = lappend(childrinfos,
adjust_appendrel_attrs(root,
(Node *) rinfo,
1, &appinfo));
}
childrel->joininfo = childrinfos;
/*
* Now for the child's targetlist.
*
* NB: the resulting childrel->reltarget->exprs may contain arbitrary
* expressions, which otherwise would not occur in a rel's targetlist.
* Code that might be looking at an appendrel child must cope with
* such. (Normally, a rel's targetlist would only include Vars and
* PlaceHolderVars.) XXX we do not bother to update the cost or width
* fields of childrel->reltarget; not clear if that would be useful.
*/
childrel->reltarget->exprs = (List *)
adjust_appendrel_attrs(root,
(Node *) rel->reltarget->exprs,
1, &appinfo);
/*
* We have to make child entries in the EquivalenceClass data
* structures as well. This is needed either if the parent
* participates in some eclass joins (because we will want to consider
* inner-indexscan joins on the individual children) or if the parent
* has useful pathkeys (because we should try to build MergeAppend
* paths that produce those sort orderings).
*/
if (rel->has_eclass_joins || has_useful_pathkeys(root, rel))
add_child_rel_equivalences(root, appinfo, rel, childrel);
childrel->has_eclass_joins = rel->has_eclass_joins;
/*
* Note: we could compute appropriate attr_needed data for the child's
* variables, by transforming the parent's attr_needed through the
* translated_vars mapping. However, currently there's no need
* because attr_needed is only examined for base relations not
* otherrels. So we just leave the child's attr_needed empty.
*/
/*
* If we consider partitionwise joins with the parent rel, do the same
* for partitioned child rels.
*
* Note: here we abuse the consider_partitionwise_join flag by setting
* it for child rels that are not themselves partitioned. We do so to
* tell try_partitionwise_join() that the child rel is sufficiently
* valid to be used as a per-partition input, even if it later gets
* proven to be dummy. (It's not usable until we've set up the
* reltarget and EC entries, which we just did.)
*/
if (rel->consider_partitionwise_join)
childrel->consider_partitionwise_join = true;
/*
* If parallelism is allowable for this query in general, see whether
* it's allowable for this childrel in particular. But if we've
* already decided the appendrel is not parallel-safe as a whole,
* there's no point in considering parallelism for this child. For
* consistency, do this before calling set_rel_size() for the child.
*/
if (root->glob->parallelModeOK && rel->consider_parallel)
set_rel_consider_parallel(root, childrel, childRTE);
/*
* Compute the child's size.
*/
set_rel_size(root, childrel, childRTindex, childRTE);
/*
* It is possible that constraint exclusion detected a contradiction
* within a child subquery, even though we didn't prove one above. If
* so, we can skip this child.
*/
if (IS_DUMMY_REL(childrel))
continue;
/* We have at least one live child. */
has_live_children = true;
/*
* If any live child is not parallel-safe, treat the whole appendrel
* as not parallel-safe. In future we might be able to generate plans
* in which some children are farmed out to workers while others are
* not; but we don't have that today, so it's a waste to consider
* partial paths anywhere in the appendrel unless it's all safe.
* (Child rels visited before this one will be unmarked in
* set_append_rel_pathlist().)
*/
if (!childrel->consider_parallel)
rel->consider_parallel = false;
/*
* Accumulate size information from each live child.
*/
Assert(childrel->rows > 0);
parent_rows += childrel->rows;
parent_size += childrel->reltarget->width * childrel->rows;
/*
* Accumulate per-column estimates too. We need not do anything for
* PlaceHolderVars in the parent list. If child expression isn't a
* Var, or we didn't record a width estimate for it, we have to fall
* back on a datatype-based estimate.
*
* By construction, child's targetlist is 1-to-1 with parent's.
*/
forboth(parentvars, rel->reltarget->exprs,
childvars, childrel->reltarget->exprs)
{
Var *parentvar = (Var *) lfirst(parentvars);
Node *childvar = (Node *) lfirst(childvars);
if (IsA(parentvar, Var) && parentvar->varno == parentRTindex)
{
int pndx = parentvar->varattno - rel->min_attr;
int32 child_width = 0;
if (IsA(childvar, Var) &&
((Var *) childvar)->varno == childrel->relid)
{
int cndx = ((Var *) childvar)->varattno - childrel->min_attr;
child_width = childrel->attr_widths[cndx];
}
if (child_width <= 0)
child_width = get_typavgwidth(exprType(childvar),
exprTypmod(childvar));
Assert(child_width > 0);
parent_attrsizes[pndx] += child_width * childrel->rows;
}
}
}
if (has_live_children)
{
/*
* Save the finished size estimates.
*/
int i;
Assert(parent_rows > 0);
rel->rows = parent_rows;
rel->reltarget->width = rint(parent_size / parent_rows);
for (i = 0; i < nattrs; i++)
rel->attr_widths[i] = rint(parent_attrsizes[i] / parent_rows);
/*
* Set "raw tuples" count equal to "rows" for the appendrel; needed
* because some places assume rel->tuples is valid for any baserel.
*/
rel->tuples = parent_rows;
/*
* Note that we leave rel->pages as zero; this is important to avoid
* double-counting the appendrel tree in total_table_pages.
*/
}
else
{
/*
* All children were excluded by constraints, so mark the whole
* appendrel dummy. We must do this in this phase so that the rel's
* dummy-ness is visible when we generate paths for other rels.
*/
set_dummy_rel_pathlist(rel);
}
pfree(parent_attrsizes);
}
/*
* set_append_rel_pathlist
* Build access paths for an "append relation"
*/
static void
set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
Index rti, RangeTblEntry *rte)
{
int parentRTindex = rti;
List *live_childrels = NIL;
ListCell *l;
/*
* Generate access paths for each member relation, and remember the
* non-dummy children.
*/
foreach(l, root->append_rel_list)
{
AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
int childRTindex;
RangeTblEntry *childRTE;
RelOptInfo *childrel;
/* append_rel_list contains all append rels; ignore others */
if (appinfo->parent_relid != parentRTindex)
continue;
/* Re-locate the child RTE and RelOptInfo */
childRTindex = appinfo->child_relid;
childRTE = root->simple_rte_array[childRTindex];
childrel = root->simple_rel_array[childRTindex];
/*
* If set_append_rel_size() decided the parent appendrel was
* parallel-unsafe at some point after visiting this child rel, we
* need to propagate the unsafety marking down to the child, so that
* we don't generate useless partial paths for it.
*/
if (!rel->consider_parallel)
childrel->consider_parallel = false;
/*
* Compute the child's access paths.
*/
set_rel_pathlist(root, childrel, childRTindex, childRTE);
/*
* If child is dummy, ignore it.
*/
if (IS_DUMMY_REL(childrel))
continue;
/*
* Child is live, so add it to the live_childrels list for use below.
*/
live_childrels = lappend(live_childrels, childrel);
}
/* Add paths to the append relation. */
add_paths_to_append_rel(root, rel, live_childrels);
}
/*
* add_paths_to_append_rel
* Generate paths for the given append relation given the set of non-dummy
* child rels.
*
* The function collects all parameterizations and orderings supported by the
* non-dummy children. For every such parameterization or ordering, it creates
* an append path collecting one path from each non-dummy child with given
* parameterization or ordering. Similarly it collects partial paths from
* non-dummy children to create partial append paths.
*/
void
add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
List *live_childrels)
{
List *subpaths = NIL;
bool subpaths_valid = true;
List *partial_subpaths = NIL;
List *pa_partial_subpaths = NIL;
List *pa_nonpartial_subpaths = NIL;
bool partial_subpaths_valid = true;
bool pa_subpaths_valid;
List *all_child_pathkeys = NIL;
List *all_child_outers = NIL;
ListCell *l;
double partial_rows = -1;
/* If appropriate, consider parallel append */
pa_subpaths_valid = enable_parallel_append && rel->consider_parallel;
/*
* For every non-dummy child, remember the cheapest path. Also, identify
* all pathkeys (orderings) and parameterizations (required_outer sets)
* available for the non-dummy member relations.
*/
foreach(l, live_childrels)
{
RelOptInfo *childrel = lfirst(l);
ListCell *lcp;
Path *cheapest_partial_path = NULL;
/*
* If child has an unparameterized cheapest-total path, add that to
* the unparameterized Append path we are constructing for the parent.
* If not, there's no workable unparameterized path.
*
* With partitionwise aggregates, the child rel's pathlist may be
* empty, so don't assume that a path exists here.
*/
if (childrel->pathlist != NIL &&
childrel->cheapest_total_path->param_info == NULL)
accumulate_append_subpath(childrel->cheapest_total_path,
&subpaths, NULL);
else
subpaths_valid = false;
/* Same idea, but for a partial plan. */
if (childrel->partial_pathlist != NIL)
{
cheapest_partial_path = linitial(childrel->partial_pathlist);
accumulate_append_subpath(cheapest_partial_path,
&partial_subpaths, NULL);
}
else
partial_subpaths_valid = false;
/*
* Same idea, but for a parallel append mixing partial and non-partial
* paths.
*/
if (pa_subpaths_valid)
{
Path *nppath = NULL;
nppath =
get_cheapest_parallel_safe_total_inner(childrel->pathlist);
if (cheapest_partial_path == NULL && nppath == NULL)
{
/* Neither a partial nor a parallel-safe path? Forget it. */
pa_subpaths_valid = false;
}
else if (nppath == NULL ||
(cheapest_partial_path != NULL &&
cheapest_partial_path->total_cost < nppath->total_cost))
{
/* Partial path is cheaper or the only option. */
Assert(cheapest_partial_path != NULL);
accumulate_append_subpath(cheapest_partial_path,
&pa_partial_subpaths,
&pa_nonpartial_subpaths);
}
else
{
/*
* Either we've got only a non-partial path, or we think that
* a single backend can execute the best non-partial path
* faster than all the parallel backends working together can
* execute the best partial path.
*
* It might make sense to be more aggressive here. Even if
* the best non-partial path is more expensive than the best
* partial path, it could still be better to choose the
* non-partial path if there are several such paths that can
* be given to different workers. For now, we don't try to
* figure that out.
*/
accumulate_append_subpath(nppath,
&pa_nonpartial_subpaths,
NULL);
}
}
/*
* Collect lists of all the available path orderings and
* parameterizations for all the children. We use these as a
* heuristic to indicate which sort orderings and parameterizations we
* should build Append and MergeAppend paths for.
*/
foreach(lcp, childrel->pathlist)
{
Path *childpath = (Path *) lfirst(lcp);
List *childkeys = childpath->pathkeys;
Relids childouter = PATH_REQ_OUTER(childpath);
/* Unsorted paths don't contribute to pathkey list */
if (childkeys != NIL)
{
ListCell *lpk;
bool found = false;
/* Have we already seen this ordering? */
foreach(lpk, all_child_pathkeys)
{
List *existing_pathkeys = (List *) lfirst(lpk);
if (compare_pathkeys(existing_pathkeys,
childkeys) == PATHKEYS_EQUAL)
{
found = true;
break;
}
}
if (!found)
{
/* No, so add it to all_child_pathkeys */
all_child_pathkeys = lappend(all_child_pathkeys,
childkeys);
}
}
/* Unparameterized paths don't contribute to param-set list */
if (childouter)
{
ListCell *lco;
bool found = false;
/* Have we already seen this param set? */
foreach(lco, all_child_outers)
{
Relids existing_outers = (Relids) lfirst(lco);
if (bms_equal(existing_outers, childouter))
{
found = true;
break;
}
}
if (!found)
{
/* No, so add it to all_child_outers */
all_child_outers = lappend(all_child_outers,
childouter);
}
}
}
}
/*
* If we found unparameterized paths for all children, build an unordered,
* unparameterized Append path for the rel. (Note: this is correct even
* if we have zero or one live subpath due to constraint exclusion.)
*/
if (subpaths_valid)
add_path(rel, (Path *) create_append_path(root, rel, subpaths, NIL,
NIL, NULL, 0, false,
-1));
/*
* Consider an append of unordered, unparameterized partial paths. Make
* it parallel-aware if possible.
*/
if (partial_subpaths_valid && partial_subpaths != NIL)
{
AppendPath *appendpath;
ListCell *lc;
int parallel_workers = 0;
/* Find the highest number of workers requested for any subpath. */
foreach(lc, partial_subpaths)
{
Path *path = lfirst(lc);
parallel_workers = Max(parallel_workers, path->parallel_workers);
}
Assert(parallel_workers > 0);
/*
* If the use of parallel append is permitted, always request at least
* log2(# of children) workers. We assume it can be useful to have
* extra workers in this case because they will be spread out across
* the children. The precise formula is just a guess, but we don't
* want to end up with a radically different answer for a table with N
* partitions vs. an unpartitioned table with the same data, so the
* use of some kind of log-scaling here seems to make some sense.
*/
if (enable_parallel_append)
{
parallel_workers = Max(parallel_workers,
pg_leftmost_one_pos32(list_length(live_childrels)) + 1);
parallel_workers = Min(parallel_workers,
max_parallel_workers_per_gather);
}
Assert(parallel_workers > 0);
/* Generate a partial append path. */
appendpath = create_append_path(root, rel, NIL, partial_subpaths,
NIL, NULL, parallel_workers,
enable_parallel_append,
-1);
/*
* Make sure any subsequent partial paths use the same row count
* estimate.
*/
partial_rows = appendpath->path.rows;
/* Add the path. */
add_partial_path(rel, (Path *) appendpath);
}
/*
* Consider a parallel-aware append using a mix of partial and non-partial
* paths. (This only makes sense if there's at least one child which has
* a non-partial path that is substantially cheaper than any partial path;
* otherwise, we should use the append path added in the previous step.)
*/
if (pa_subpaths_valid && pa_nonpartial_subpaths != NIL)
{
AppendPath *appendpath;
ListCell *lc;
int parallel_workers = 0;
/*
* Find the highest number of workers requested for any partial
* subpath.
*/
foreach(lc, pa_partial_subpaths)
{
Path *path = lfirst(lc);
parallel_workers = Max(parallel_workers, path->parallel_workers);
}
/*
* Same formula here as above. It's even more important in this
* instance because the non-partial paths won't contribute anything to
* the planned number of parallel workers.
*/
parallel_workers = Max(parallel_workers,
pg_leftmost_one_pos32(list_length(live_childrels)) + 1);
parallel_workers = Min(parallel_workers,
max_parallel_workers_per_gather);
Assert(parallel_workers > 0);
appendpath = create_append_path(root, rel, pa_nonpartial_subpaths,
pa_partial_subpaths,
NIL, NULL, parallel_workers, true,
partial_rows);
add_partial_path(rel, (Path *) appendpath);
}
/*
* Also build unparameterized ordered append paths based on the collected
* list of child pathkeys.
*/
if (subpaths_valid)
generate_orderedappend_paths(root, rel, live_childrels,
all_child_pathkeys);
/*
* Build Append paths for each parameterization seen among the child rels.
* (This may look pretty expensive, but in most cases of practical
* interest, the child rels will expose mostly the same parameterizations,
* so that not that many cases actually get considered here.)
*
* The Append node itself cannot enforce quals, so all qual checking must
* be done in the child paths. This means that to have a parameterized
* Append path, we must have the exact same parameterization for each
* child path; otherwise some children might be failing to check the
* moved-down quals. To make them match up, we can try to increase the
* parameterization of lesser-parameterized paths.
*/
foreach(l, all_child_outers)
{
Relids required_outer = (Relids) lfirst(l);
ListCell *lcr;
/* Select the child paths for an Append with this parameterization */
subpaths = NIL;
subpaths_valid = true;
foreach(lcr, live_childrels)
{
RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
Path *subpath;
if (childrel->pathlist == NIL)
{
/* failed to make a suitable path for this child */
subpaths_valid = false;
break;
}
subpath = get_cheapest_parameterized_child_path(root,
childrel,
required_outer);
if (subpath == NULL)
{
/* failed to make a suitable path for this child */
subpaths_valid = false;
break;
}
accumulate_append_subpath(subpath, &subpaths, NULL);
}
if (subpaths_valid)
add_path(rel, (Path *)
create_append_path(root, rel, subpaths, NIL,
NIL, required_outer, 0, false,
-1));
}
/*
* When there is only a single child relation, the Append path can inherit
* any ordering available for the child rel's path, so that it's useful to
* consider ordered partial paths. Above we only considered the cheapest
* partial path for each child, but let's also make paths using any
* partial paths that have pathkeys.
*/
if (list_length(live_childrels) == 1)
{
RelOptInfo *childrel = (RelOptInfo *) linitial(live_childrels);
/* skip the cheapest partial path, since we already used that above */
for_each_from(l, childrel->partial_pathlist, 1)
{
Path *path = (Path *) lfirst(l);
AppendPath *appendpath;
/* skip paths with no pathkeys. */
if (path->pathkeys == NIL)
continue;
appendpath = create_append_path(root, rel, NIL, list_make1(path),
NIL, NULL,
path->parallel_workers, true,
partial_rows);
add_partial_path(rel, (Path *) appendpath);
}
}
}
/*
* generate_orderedappend_paths
* Generate ordered append paths for an append relation
*
* Usually we generate MergeAppend paths here, but there are some special
* cases where we can generate simple Append paths, because the subpaths
* can provide tuples in the required order already.
*
* We generate a path for each ordering (pathkey list) appearing in
* all_child_pathkeys.
*
* We consider both cheapest-startup and cheapest-total cases, ie, for each
* interesting ordering, collect all the cheapest startup subpaths and all the
* cheapest total paths, and build a suitable path for each case.
*
* We don't currently generate any parameterized ordered paths here. While
* it would not take much more code here to do so, it's very unclear that it
* is worth the planning cycles to investigate such paths: there's little
* use for an ordered path on the inside of a nestloop. In fact, it's likely
* that the current coding of add_path would reject such paths out of hand,
* because add_path gives no credit for sort ordering of parameterized paths,
* and a parameterized MergeAppend is going to be more expensive than the
* corresponding parameterized Append path. If we ever try harder to support
* parameterized mergejoin plans, it might be worth adding support for
* parameterized paths here to feed such joins. (See notes in
* optimizer/README for why that might not ever happen, though.)
*/
static void
generate_orderedappend_paths(PlannerInfo *root, RelOptInfo *rel,
List *live_childrels,
List *all_child_pathkeys)
{
ListCell *lcp;
List *partition_pathkeys = NIL;
List *partition_pathkeys_desc = NIL;
bool partition_pathkeys_partial = true;
bool partition_pathkeys_desc_partial = true;
/*
* Some partitioned table setups may allow us to use an Append node
* instead of a MergeAppend. This is possible in cases such as RANGE
* partitioned tables where it's guaranteed that an earlier partition must
* contain rows which come earlier in the sort order. To detect whether
* this is relevant, build pathkey descriptions of the partition ordering,
* for both forward and reverse scans.
*/
if (rel->part_scheme != NULL && IS_SIMPLE_REL(rel) &&
partitions_are_ordered(rel->boundinfo, rel->live_parts))
{
partition_pathkeys = build_partition_pathkeys(root, rel,
ForwardScanDirection,
&partition_pathkeys_partial);
partition_pathkeys_desc = build_partition_pathkeys(root, rel,
BackwardScanDirection,
&partition_pathkeys_desc_partial);
/*
* You might think we should truncate_useless_pathkeys here, but
* allowing partition keys which are a subset of the query's pathkeys
* can often be useful. For example, consider a table partitioned by
* RANGE (a, b), and a query with ORDER BY a, b, c. If we have child
* paths that can produce the a, b, c ordering (perhaps via indexes on
* (a, b, c)) then it works to consider the appendrel output as
* ordered by a, b, c.
*/
}
/* Now consider each interesting sort ordering */
foreach(lcp, all_child_pathkeys)
{
List *pathkeys = (List *) lfirst(lcp);
List *startup_subpaths = NIL;
List *total_subpaths = NIL;
List *fractional_subpaths = NIL;
bool startup_neq_total = false;
bool match_partition_order;
bool match_partition_order_desc;
int end_index;
int first_index;
int direction;
/*
* Determine if this sort ordering matches any partition pathkeys we
* have, for both ascending and descending partition order. If the
* partition pathkeys happen to be contained in pathkeys then it still
* works, as described above, providing that the partition pathkeys
* are complete and not just a prefix of the partition keys. (In such
* cases we'll be relying on the child paths to have sorted the
* lower-order columns of the required pathkeys.)
*/
match_partition_order =
pathkeys_contained_in(pathkeys, partition_pathkeys) ||
(!partition_pathkeys_partial &&
pathkeys_contained_in(partition_pathkeys, pathkeys));
match_partition_order_desc = !match_partition_order &&
(pathkeys_contained_in(pathkeys, partition_pathkeys_desc) ||
(!partition_pathkeys_desc_partial &&
pathkeys_contained_in(partition_pathkeys_desc, pathkeys)));
/*
* When the required pathkeys match the reverse of the partition
* order, we must build the list of paths in reverse starting with the
* last matching partition first. We can get away without making any
* special cases for this in the loop below by just looping backward
* over the child relations in this case.
*/
if (match_partition_order_desc)
{
/* loop backward */
first_index = list_length(live_childrels) - 1;
end_index = -1;
direction = -1;
/*
* Set this to true to save us having to check for
* match_partition_order_desc in the loop below.
*/
match_partition_order = true;
}
else
{
/* for all other case, loop forward */
first_index = 0;
end_index = list_length(live_childrels);
direction = 1;
}
/* Select the child paths for this ordering... */
for (int i = first_index; i != end_index; i += direction)
{
RelOptInfo *childrel = list_nth_node(RelOptInfo, live_childrels, i);
Path *cheapest_startup,
*cheapest_total,
*cheapest_fractional = NULL;
/* Locate the right paths, if they are available. */
cheapest_startup =
get_cheapest_path_for_pathkeys(childrel->pathlist,
pathkeys,
NULL,
STARTUP_COST,
false);
cheapest_total =
get_cheapest_path_for_pathkeys(childrel->pathlist,
pathkeys,
NULL,
TOTAL_COST,
false);
/*
* If we can't find any paths with the right order just use the
* cheapest-total path; we'll have to sort it later.
*/
if (cheapest_startup == NULL || cheapest_total == NULL)
{
cheapest_startup = cheapest_total =
childrel->cheapest_total_path;
/* Assert we do have an unparameterized path for this child */
Assert(cheapest_total->param_info == NULL);
}
/*
* When building a fractional path, determine a cheapest
* fractional path for each child relation too. Looking at startup
* and total costs is not enough, because the cheapest fractional
* path may be dominated by two separate paths (one for startup,
* one for total).
*
* When needed (building fractional path), determine the cheapest
* fractional path too.
*/
if (root->tuple_fraction > 0)
{
double path_fraction = (1.0 / root->tuple_fraction);
cheapest_fractional =
get_cheapest_fractional_path_for_pathkeys(childrel->pathlist,
pathkeys,
NULL,
path_fraction);
/*
* If we found no path with matching pathkeys, use the
* cheapest total path instead.
*
* XXX We might consider partially sorted paths too (with an
* incremental sort on top). But we'd have to build all the
* incremental paths, do the costing etc.
*/
if (!cheapest_fractional)
cheapest_fractional = cheapest_total;
}
/*
* Notice whether we actually have different paths for the
* "cheapest" and "total" cases; frequently there will be no point
* in two create_merge_append_path() calls.
*/
if (cheapest_startup != cheapest_total)
startup_neq_total = true;
/*
* Collect the appropriate child paths. The required logic varies
* for the Append and MergeAppend cases.
*/
if (match_partition_order)
{
/*
* We're going to make a plain Append path. We don't need
* most of what accumulate_append_subpath would do, but we do
* want to cut out child Appends or MergeAppends if they have
* just a single subpath (and hence aren't doing anything
* useful).
*/
cheapest_startup = get_singleton_append_subpath(cheapest_startup);
cheapest_total = get_singleton_append_subpath(cheapest_total);
startup_subpaths = lappend(startup_subpaths, cheapest_startup);
total_subpaths = lappend(total_subpaths, cheapest_total);
if (cheapest_fractional)
{
cheapest_fractional = get_singleton_append_subpath(cheapest_fractional);
fractional_subpaths = lappend(fractional_subpaths, cheapest_fractional);
}
}
else
{
/*
* Otherwise, rely on accumulate_append_subpath to collect the
* child paths for the MergeAppend.
*/
accumulate_append_subpath(cheapest_startup,
&startup_subpaths, NULL);
accumulate_append_subpath(cheapest_total,
&total_subpaths, NULL);
if (cheapest_fractional)
accumulate_append_subpath(cheapest_fractional,
&fractional_subpaths, NULL);
}
}
/* ... and build the Append or MergeAppend paths */
if (match_partition_order)
{
/* We only need Append */
add_path(rel, (Path *) create_append_path(root,
rel,
startup_subpaths,
NIL,
pathkeys,
NULL,
0,
false,
-1));
if (startup_neq_total)
add_path(rel, (Path *) create_append_path(root,
rel,
total_subpaths,
NIL,
pathkeys,
NULL,
0,
false,
-1));
if (fractional_subpaths)
add_path(rel, (Path *) create_append_path(root,
rel,
fractional_subpaths,
NIL,
pathkeys,
NULL,
0,
false,
-1));
}
else
{
/* We need MergeAppend */
add_path(rel, (Path *) create_merge_append_path(root,
rel,
startup_subpaths,
pathkeys,
NULL));
if (startup_neq_total)
add_path(rel, (Path *) create_merge_append_path(root,
rel,
total_subpaths,
pathkeys,
NULL));
if (fractional_subpaths)
add_path(rel, (Path *) create_merge_append_path(root,
rel,
fractional_subpaths,
pathkeys,
NULL));
}
}
}
/*
* get_cheapest_parameterized_child_path
* Get cheapest path for this relation that has exactly the requested
* parameterization.
*
* Returns NULL if unable to create such a path.
*/
static Path *
get_cheapest_parameterized_child_path(PlannerInfo *root, RelOptInfo *rel,
Relids required_outer)
{
Path *cheapest;
ListCell *lc;
/*
* Look up the cheapest existing path with no more than the needed
* parameterization. If it has exactly the needed parameterization, we're
* done.
*/
cheapest = get_cheapest_path_for_pathkeys(rel->pathlist,
NIL,
required_outer,
TOTAL_COST,
false);
Assert(cheapest != NULL);
if (bms_equal(PATH_REQ_OUTER(cheapest), required_outer))
return cheapest;
/*
* Otherwise, we can "reparameterize" an existing path to match the given
* parameterization, which effectively means pushing down additional
* joinquals to be checked within the path's scan. However, some existing
* paths might check the available joinquals already while others don't;
* therefore, it's not clear which existing path will be cheapest after
* reparameterization. We have to go through them all and find out.
*/
cheapest = NULL;
foreach(lc, rel->pathlist)
{
Path *path = (Path *) lfirst(lc);
/* Can't use it if it needs more than requested parameterization */
if (!bms_is_subset(PATH_REQ_OUTER(path), required_outer))
continue;
/*
* Reparameterization can only increase the path's cost, so if it's
* already more expensive than the current cheapest, forget it.
*/
if (cheapest != NULL &&
compare_path_costs(cheapest, path, TOTAL_COST) <= 0)
continue;
/* Reparameterize if needed, then recheck cost */
if (!bms_equal(PATH_REQ_OUTER(path), required_outer))
{
path = reparameterize_path(root, path, required_outer, 1.0);
if (path == NULL)
continue; /* failed to reparameterize this one */
Assert(bms_equal(PATH_REQ_OUTER(path), required_outer));
if (cheapest != NULL &&
compare_path_costs(cheapest, path, TOTAL_COST) <= 0)
continue;
}
/* We have a new best path */
cheapest = path;
}
/* Return the best path, or NULL if we found no suitable candidate */
return cheapest;
}
/*
* accumulate_append_subpath
* Add a subpath to the list being built for an Append or MergeAppend.
*
* It's possible that the child is itself an Append or MergeAppend path, in
* which case we can "cut out the middleman" and just add its child paths to
* our own list. (We don't try to do this earlier because we need to apply
* both levels of transformation to the quals.)
*
* Note that if we omit a child MergeAppend in this way, we are effectively
* omitting a sort step, which seems fine: if the parent is to be an Append,
* its result would be unsorted anyway, while if the parent is to be a
* MergeAppend, there's no point in a separate sort on a child.
*
* Normally, either path is a partial path and subpaths is a list of partial
* paths, or else path is a non-partial plan and subpaths is a list of those.
* However, if path is a parallel-aware Append, then we add its partial path
* children to subpaths and the rest to special_subpaths. If the latter is
* NULL, we don't flatten the path at all (unless it contains only partial
* paths).
*/
static void
accumulate_append_subpath(Path *path, List **subpaths, List **special_subpaths)
{
if (IsA(path, AppendPath))
{
AppendPath *apath = (AppendPath *) path;
if (!apath->path.parallel_aware || apath->first_partial_path == 0)
{
*subpaths = list_concat(*subpaths, apath->subpaths);
return;
}
else if (special_subpaths != NULL)
{
List *new_special_subpaths;
/* Split Parallel Append into partial and non-partial subpaths */
*subpaths = list_concat(*subpaths,
list_copy_tail(apath->subpaths,
apath->first_partial_path));
new_special_subpaths = list_copy_head(apath->subpaths,
apath->first_partial_path);
*special_subpaths = list_concat(*special_subpaths,
new_special_subpaths);
return;
}
}
else if (IsA(path, MergeAppendPath))
{
MergeAppendPath *mpath = (MergeAppendPath *) path;
*subpaths = list_concat(*subpaths, mpath->subpaths);
return;
}
*subpaths = lappend(*subpaths, path);
}
/*
* get_singleton_append_subpath
* Returns the single subpath of an Append/MergeAppend, or just
* return 'path' if it's not a single sub-path Append/MergeAppend.
*
* Note: 'path' must not be a parallel-aware path.
*/
static Path *
get_singleton_append_subpath(Path *path)
{
Assert(!path->parallel_aware);
if (IsA(path, AppendPath))
{
AppendPath *apath = (AppendPath *) path;
if (list_length(apath->subpaths) == 1)
return (Path *) linitial(apath->subpaths);
}
else if (IsA(path, MergeAppendPath))
{
MergeAppendPath *mpath = (MergeAppendPath *) path;
if (list_length(mpath->subpaths) == 1)
return (Path *) linitial(mpath->subpaths);
}
return path;
}
/*
* set_dummy_rel_pathlist
* Build a dummy path for a relation that's been excluded by constraints
*
* Rather than inventing a special "dummy" path type, we represent this as an
* AppendPath with no members (see also IS_DUMMY_APPEND/IS_DUMMY_REL macros).
*
* (See also mark_dummy_rel, which does basically the same thing, but is
* typically used to change a rel into dummy state after we already made
* paths for it.)
*/
static void
set_dummy_rel_pathlist(RelOptInfo *rel)
{
/* Set dummy size estimates --- we leave attr_widths[] as zeroes */
rel->rows = 0;
rel->reltarget->width = 0;
/* Discard any pre-existing paths; no further need for them */
rel->pathlist = NIL;
rel->partial_pathlist = NIL;
/* Set up the dummy path */
add_path(rel, (Path *) create_append_path(NULL, rel, NIL, NIL,
NIL, rel->lateral_relids,
0, false, -1));
/*
* We set the cheapest-path fields immediately, just in case they were
* pointing at some discarded path. This is redundant when we're called
* from set_rel_size(), but not when called from elsewhere, and doing it
* twice is harmless anyway.
*/
set_cheapest(rel);
}
/* quick-and-dirty test to see if any joining is needed */
static bool
has_multiple_baserels(PlannerInfo *root)
{
int num_base_rels = 0;
Index rti;
for (rti = 1; rti < root->simple_rel_array_size; rti++)
{
RelOptInfo *brel = root->simple_rel_array[rti];
if (brel == NULL)
continue;
/* ignore RTEs that are "other rels" */
if (brel->reloptkind == RELOPT_BASEREL)
if (++num_base_rels > 1)
return true;
}
return false;
}
/*
* find_window_run_conditions
* Determine if 'wfunc' is really a WindowFunc and call its prosupport
* function to determine the function's monotonic properties. We then
* see if 'opexpr' can be used to short-circuit execution.
*
* For example row_number() over (order by ...) always produces a value one
* higher than the previous. If someone has a window function in a subquery
* and has a WHERE clause in the outer query to filter rows <= 10, then we may
* as well stop processing the windowagg once the row number reaches 11. Here
* we check if 'opexpr' might help us to stop doing needless extra processing
* in WindowAgg nodes.
*
* '*keep_original' is set to true if the caller should also use 'opexpr' for
* its original purpose. This is set to false if the caller can assume that
* the run condition will handle all of the required filtering.
*
* Returns true if 'opexpr' was found to be useful and was added to the
* WindowClauses runCondition. We also set *keep_original accordingly and add
* 'attno' to *run_cond_attrs offset by FirstLowInvalidHeapAttributeNumber.
* If the 'opexpr' cannot be used then we set *keep_original to true and
* return false.
*/
static bool
find_window_run_conditions(Query *subquery, RangeTblEntry *rte, Index rti,
AttrNumber attno, WindowFunc *wfunc, OpExpr *opexpr,
bool wfunc_left, bool *keep_original,
Bitmapset **run_cond_attrs)
{
Oid prosupport;
Expr *otherexpr;
SupportRequestWFuncMonotonic req;
SupportRequestWFuncMonotonic *res;
WindowClause *wclause;
List *opinfos;
OpExpr *runopexpr;
Oid runoperator;
ListCell *lc;
*keep_original = true;
while (IsA(wfunc, RelabelType))
wfunc = (WindowFunc *) ((RelabelType *) wfunc)->arg;
/* we can only work with window functions */
if (!IsA(wfunc, WindowFunc))
return false;
/* can't use it if there are subplans in the WindowFunc */
if (contain_subplans((Node *) wfunc))
return false;
prosupport = get_func_support(wfunc->winfnoid);
/* Check if there's a support function for 'wfunc' */
if (!OidIsValid(prosupport))
return false;
/* get the Expr from the other side of the OpExpr */
if (wfunc_left)
otherexpr = lsecond(opexpr->args);
else
otherexpr = linitial(opexpr->args);
/*
* The value being compared must not change during the evaluation of the
* window partition.
*/
if (!is_pseudo_constant_clause((Node *) otherexpr))
return false;
/* find the window clause belonging to the window function */
wclause = (WindowClause *) list_nth(subquery->windowClause,
wfunc->winref - 1);
req.type = T_SupportRequestWFuncMonotonic;
req.window_func = wfunc;
req.window_clause = wclause;
/* call the support function */
res = (SupportRequestWFuncMonotonic *)
DatumGetPointer(OidFunctionCall1(prosupport,
PointerGetDatum(&req)));
/*
* Nothing to do if the function is neither monotonically increasing nor
* monotonically decreasing.
*/
if (res == NULL || res->monotonic == MONOTONICFUNC_NONE)
return false;
runopexpr = NULL;
runoperator = InvalidOid;
opinfos = get_op_btree_interpretation(opexpr->opno);
foreach(lc, opinfos)
{
OpBtreeInterpretation *opinfo = (OpBtreeInterpretation *) lfirst(lc);
int strategy = opinfo->strategy;
/* handle < / <= */
if (strategy == BTLessStrategyNumber ||
strategy == BTLessEqualStrategyNumber)
{
/*
* < / <= is supported for monotonically increasing functions in
* the form <wfunc> op <pseudoconst> and <pseudoconst> op <wfunc>
* for monotonically decreasing functions.
*/
if ((wfunc_left && (res->monotonic & MONOTONICFUNC_INCREASING)) ||
(!wfunc_left && (res->monotonic & MONOTONICFUNC_DECREASING)))
{
*keep_original = false;
runopexpr = opexpr;
runoperator = opexpr->opno;
}
break;
}
/* handle > / >= */
else if (strategy == BTGreaterStrategyNumber ||
strategy == BTGreaterEqualStrategyNumber)
{
/*
* > / >= is supported for monotonically decreasing functions in
* the form <wfunc> op <pseudoconst> and <pseudoconst> op <wfunc>
* for monotonically increasing functions.
*/
if ((wfunc_left && (res->monotonic & MONOTONICFUNC_DECREASING)) ||
(!wfunc_left && (res->monotonic & MONOTONICFUNC_INCREASING)))
{
*keep_original = false;
runopexpr = opexpr;
runoperator = opexpr->opno;
}
break;
}
/* handle = */
else if (strategy == BTEqualStrategyNumber)
{
int16 newstrategy;
/*
* When both monotonically increasing and decreasing then the
* return value of the window function will be the same each time.
* We can simply use 'opexpr' as the run condition without
* modifying it.
*/
if ((res->monotonic & MONOTONICFUNC_BOTH) == MONOTONICFUNC_BOTH)
{
*keep_original = false;
runopexpr = opexpr;
runoperator = opexpr->opno;
break;
}
/*
* When monotonically increasing we make a qual with <wfunc> <=
* <value> or <value> >= <wfunc> in order to filter out values
* which are above the value in the equality condition. For
* monotonically decreasing functions we want to filter values
* below the value in the equality condition.
*/
if (res->monotonic & MONOTONICFUNC_INCREASING)
newstrategy = wfunc_left ? BTLessEqualStrategyNumber : BTGreaterEqualStrategyNumber;
else
newstrategy = wfunc_left ? BTGreaterEqualStrategyNumber : BTLessEqualStrategyNumber;
/* We must keep the original equality qual */
*keep_original = true;
runopexpr = opexpr;
/* determine the operator to use for the runCondition qual */
runoperator = get_opfamily_member(opinfo->opfamily_id,
opinfo->oplefttype,
opinfo->oprighttype,
newstrategy);
break;
}
}
if (runopexpr != NULL)
{
Expr *newexpr;
/*
* Build the qual required for the run condition keeping the
* WindowFunc on the same side as it was originally.
*/
if (wfunc_left)
newexpr = make_opclause(runoperator,
runopexpr->opresulttype,
runopexpr->opretset, (Expr *) wfunc,
otherexpr, runopexpr->opcollid,
runopexpr->inputcollid);
else
newexpr = make_opclause(runoperator,
runopexpr->opresulttype,
runopexpr->opretset,
otherexpr, (Expr *) wfunc,
runopexpr->opcollid,
runopexpr->inputcollid);
wclause->runCondition = lappend(wclause->runCondition, newexpr);
/* record that this attno was used in a run condition */
*run_cond_attrs = bms_add_member(*run_cond_attrs,
attno - FirstLowInvalidHeapAttributeNumber);
return true;
}
/* unsupported OpExpr */
return false;
}
/*
* check_and_push_window_quals
* Check if 'clause' is a qual that can be pushed into a WindowFunc's
* WindowClause as a 'runCondition' qual. These, when present, allow
* some unnecessary work to be skipped during execution.
*
* 'run_cond_attrs' will be populated with all targetlist resnos of subquery
* targets (offset by FirstLowInvalidHeapAttributeNumber) that we pushed
* window quals for.
*
* Returns true if the caller still must keep the original qual or false if
* the caller can safely ignore the original qual because the WindowAgg node
* will use the runCondition to stop returning tuples.
*/
static bool
check_and_push_window_quals(Query *subquery, RangeTblEntry *rte, Index rti,
Node *clause, Bitmapset **run_cond_attrs)
{
OpExpr *opexpr = (OpExpr *) clause;
bool keep_original = true;
Var *var1;
Var *var2;
/* We're only able to use OpExprs with 2 operands */
if (!IsA(opexpr, OpExpr))
return true;
if (list_length(opexpr->args) != 2)
return true;
/*
* Currently, we restrict this optimization to strict OpExprs. The reason
* for this is that during execution, once the runcondition becomes false,
* we stop evaluating WindowFuncs. To avoid leaving around stale window
* function result values, we set them to NULL. Having only strict
* OpExprs here ensures that we properly filter out the tuples with NULLs
* in the top-level WindowAgg.
*/
set_opfuncid(opexpr);
if (!func_strict(opexpr->opfuncid))
return true;
/*
* Check for plain Vars that reference window functions in the subquery.
* If we find any, we'll ask find_window_run_conditions() if 'opexpr' can
* be used as part of the run condition.
*/
/* Check the left side of the OpExpr */
var1 = linitial(opexpr->args);
if (IsA(var1, Var) && var1->varattno > 0)
{
TargetEntry *tle = list_nth(subquery->targetList, var1->varattno - 1);
WindowFunc *wfunc = (WindowFunc *) tle->expr;
if (find_window_run_conditions(subquery, rte, rti, tle->resno, wfunc,
opexpr, true, &keep_original,
run_cond_attrs))
return keep_original;
}
/* and check the right side */
var2 = lsecond(opexpr->args);
if (IsA(var2, Var) && var2->varattno > 0)
{
TargetEntry *tle = list_nth(subquery->targetList, var2->varattno - 1);
WindowFunc *wfunc = (WindowFunc *) tle->expr;
if (find_window_run_conditions(subquery, rte, rti, tle->resno, wfunc,
opexpr, false, &keep_original,
run_cond_attrs))
return keep_original;
}
return true;
}
/*
* set_subquery_pathlist
* Generate SubqueryScan access paths for a subquery RTE
*
* We don't currently support generating parameterized paths for subqueries
* by pushing join clauses down into them; it seems too expensive to re-plan
* the subquery multiple times to consider different alternatives.
* (XXX that could stand to be reconsidered, now that we use Paths.)
* So the paths made here will be parameterized if the subquery contains
* LATERAL references, otherwise not. As long as that's true, there's no need
* for a separate set_subquery_size phase: just make the paths right away.
*/
static void
set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
Index rti, RangeTblEntry *rte)
{
Query *parse = root->parse;
Query *subquery = rte->subquery;
bool trivial_pathtarget;
Relids required_outer;
pushdown_safety_info safetyInfo;
double tuple_fraction;
RelOptInfo *sub_final_rel;
Bitmapset *run_cond_attrs = NULL;
ListCell *lc;
/*
* Must copy the Query so that planning doesn't mess up the RTE contents
* (really really need to fix the planner to not scribble on its input,
* someday ... but see remove_unused_subquery_outputs to start with).
*/
subquery = copyObject(subquery);
/*
* If it's a LATERAL subquery, it might contain some Vars of the current
* query level, requiring it to be treated as parameterized, even though
* we don't support pushing down join quals into subqueries.
*/
required_outer = rel->lateral_relids;
/*
* Zero out result area for subquery_is_pushdown_safe, so that it can set
* flags as needed while recursing. In particular, we need a workspace
* for keeping track of the reasons why columns are unsafe to reference.
* These reasons are stored in the bits inside unsafeFlags[i] when we
* discover reasons that column i of the subquery is unsafe to be used in
* a pushed-down qual.
*/
memset(&safetyInfo, 0, sizeof(safetyInfo));
safetyInfo.unsafeFlags = (unsigned char *)
palloc0((list_length(subquery->targetList) + 1) * sizeof(unsigned char));
/*
* If the subquery has the "security_barrier" flag, it means the subquery
* originated from a view that must enforce row-level security. Then we
* must not push down quals that contain leaky functions. (Ideally this
* would be checked inside subquery_is_pushdown_safe, but since we don't
* currently pass the RTE to that function, we must do it here.)
*/
safetyInfo.unsafeLeaky = rte->security_barrier;
/*
* If there are any restriction clauses that have been attached to the
* subquery relation, consider pushing them down to become WHERE or HAVING
* quals of the subquery itself. This transformation is useful because it
* may allow us to generate a better plan for the subquery than evaluating
* all the subquery output rows and then filtering them.
*
* There are several cases where we cannot push down clauses. Restrictions
* involving the subquery are checked by subquery_is_pushdown_safe().
* Restrictions on individual clauses are checked by
* qual_is_pushdown_safe(). Also, we don't want to push down
* pseudoconstant clauses; better to have the gating node above the
* subquery.
*
* Non-pushed-down clauses will get evaluated as qpquals of the
* SubqueryScan node.
*
* XXX Are there any cases where we want to make a policy decision not to
* push down a pushable qual, because it'd result in a worse plan?
*/
if (rel->baserestrictinfo != NIL &&
subquery_is_pushdown_safe(subquery, subquery, &safetyInfo))
{
/* OK to consider pushing down individual quals */
List *upperrestrictlist = NIL;
ListCell *l;
foreach(l, rel->baserestrictinfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
Node *clause = (Node *) rinfo->clause;
if (rinfo->pseudoconstant)
{
upperrestrictlist = lappend(upperrestrictlist, rinfo);
continue;
}
switch (qual_is_pushdown_safe(subquery, rti, rinfo, &safetyInfo))
{
case PUSHDOWN_SAFE:
/* Push it down */
subquery_push_qual(subquery, rte, rti, clause);
break;
case PUSHDOWN_WINDOWCLAUSE_RUNCOND:
/*
* Since we can't push the qual down into the subquery,
* check if it happens to reference a window function. If
* so then it might be useful to use for the WindowAgg's
* runCondition.
*/
if (!subquery->hasWindowFuncs ||
check_and_push_window_quals(subquery, rte, rti, clause,
&run_cond_attrs))
{
/*
* subquery has no window funcs or the clause is not a
* suitable window run condition qual or it is, but
* the original must also be kept in the upper query.
*/
upperrestrictlist = lappend(upperrestrictlist, rinfo);
}
break;
case PUSHDOWN_UNSAFE:
upperrestrictlist = lappend(upperrestrictlist, rinfo);
break;
}
}
rel->baserestrictinfo = upperrestrictlist;
/* We don't bother recomputing baserestrict_min_security */
}
pfree(safetyInfo.unsafeFlags);
/*
* The upper query might not use all the subquery's output columns; if
* not, we can simplify. Pass the attributes that were pushed down into
* WindowAgg run conditions to ensure we don't accidentally think those
* are unused.
*/
remove_unused_subquery_outputs(subquery, rel, run_cond_attrs);
/*
* We can safely pass the outer tuple_fraction down to the subquery if the
* outer level has no joining, aggregation, or sorting to do. Otherwise
* we'd better tell the subquery to plan for full retrieval. (XXX This
* could probably be made more intelligent ...)
*/
if (parse->hasAggs ||
parse->groupClause ||
parse->groupingSets ||
root->hasHavingQual ||
parse->distinctClause ||
parse->sortClause ||
has_multiple_baserels(root))
tuple_fraction = 0.0; /* default case */
else
tuple_fraction = root->tuple_fraction;
/* plan_params should not be in use in current query level */
Assert(root->plan_params == NIL);
/* Generate a subroot and Paths for the subquery */
rel->subroot = subquery_planner(root->glob, subquery,
root,
false, tuple_fraction);
/* Isolate the params needed by this specific subplan */
rel->subplan_params = root->plan_params;
root->plan_params = NIL;
/*
* It's possible that constraint exclusion proved the subquery empty. If
* so, it's desirable to produce an unadorned dummy path so that we will
* recognize appropriate optimizations at this query level.
*/
sub_final_rel = fetch_upper_rel(rel->subroot, UPPERREL_FINAL, NULL);
if (IS_DUMMY_REL(sub_final_rel))
{
set_dummy_rel_pathlist(rel);
return;
}
/*
* Mark rel with estimated output rows, width, etc. Note that we have to
* do this before generating outer-query paths, else cost_subqueryscan is
* not happy.
*/
set_subquery_size_estimates(root, rel);
/*
* Also detect whether the reltarget is trivial, so that we can pass that
* info to cost_subqueryscan (rather than re-deriving it multiple times).
* It's trivial if it fetches all the subplan output columns in order.
*/
if (list_length(rel->reltarget->exprs) != list_length(subquery->targetList))
trivial_pathtarget = false;
else
{
trivial_pathtarget = true;
foreach(lc, rel->reltarget->exprs)
{
Node *node = (Node *) lfirst(lc);
Var *var;
if (!IsA(node, Var))
{
trivial_pathtarget = false;
break;
}
var = (Var *) node;
if (var->varno != rti ||
var->varattno != foreach_current_index(lc) + 1)
{
trivial_pathtarget = false;
break;
}
}
}
/*
* For each Path that subquery_planner produced, make a SubqueryScanPath
* in the outer query.
*/
foreach(lc, sub_final_rel->pathlist)
{
Path *subpath = (Path *) lfirst(lc);
List *pathkeys;
/* Convert subpath's pathkeys to outer representation */
pathkeys = convert_subquery_pathkeys(root,
rel,
subpath->pathkeys,
make_tlist_from_pathtarget(subpath->pathtarget));
/* Generate outer path using this subpath */
add_path(rel, (Path *)
create_subqueryscan_path(root, rel, subpath,
trivial_pathtarget,
pathkeys, required_outer));
}
/* If outer rel allows parallelism, do same for partial paths. */
if (rel->consider_parallel && bms_is_empty(required_outer))
{
/* If consider_parallel is false, there should be no partial paths. */
Assert(sub_final_rel->consider_parallel ||
sub_final_rel->partial_pathlist == NIL);
/* Same for partial paths. */
foreach(lc, sub_final_rel->partial_pathlist)
{
Path *subpath = (Path *) lfirst(lc);
List *pathkeys;
/* Convert subpath's pathkeys to outer representation */
pathkeys = convert_subquery_pathkeys(root,
rel,
subpath->pathkeys,
make_tlist_from_pathtarget(subpath->pathtarget));
/* Generate outer path using this subpath */
add_partial_path(rel, (Path *)
create_subqueryscan_path(root, rel, subpath,
trivial_pathtarget,
pathkeys,
required_outer));
}
}
}
/*
* set_function_pathlist
* Build the (single) access path for a function RTE
*/
static void
set_function_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
Relids required_outer;
List *pathkeys = NIL;
/*
* We don't support pushing join clauses into the quals of a function
* scan, but it could still have required parameterization due to LATERAL
* refs in the function expression.
*/
required_outer = rel->lateral_relids;
/*
* The result is considered unordered unless ORDINALITY was used, in which
* case it is ordered by the ordinal column (the last one). See if we
* care, by checking for uses of that Var in equivalence classes.
*/
if (rte->funcordinality)
{
AttrNumber ordattno = rel->max_attr;
Var *var = NULL;
ListCell *lc;
/*
* Is there a Var for it in rel's targetlist? If not, the query did
* not reference the ordinality column, or at least not in any way
* that would be interesting for sorting.
*/
foreach(lc, rel->reltarget->exprs)
{
Var *node = (Var *) lfirst(lc);
/* checking varno/varlevelsup is just paranoia */
if (IsA(node, Var) &&
node->varattno == ordattno &&
node->varno == rel->relid &&
node->varlevelsup == 0)
{
var = node;
break;
}
}
/*
* Try to build pathkeys for this Var with int8 sorting. We tell
* build_expression_pathkey not to build any new equivalence class; if
* the Var isn't already mentioned in some EC, it means that nothing
* cares about the ordering.
*/
if (var)
pathkeys = build_expression_pathkey(root,
(Expr *) var,
Int8LessOperator,
rel->relids,
false);
}
/* Generate appropriate path */
add_path(rel, create_functionscan_path(root, rel,
pathkeys, required_outer));
}
/*
* set_values_pathlist
* Build the (single) access path for a VALUES RTE
*/
static void
set_values_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
Relids required_outer;
/*
* We don't support pushing join clauses into the quals of a values scan,
* but it could still have required parameterization due to LATERAL refs
* in the values expressions.
*/
required_outer = rel->lateral_relids;
/* Generate appropriate path */
add_path(rel, create_valuesscan_path(root, rel, required_outer));
}
/*
* set_tablefunc_pathlist
* Build the (single) access path for a table func RTE
*/
static void
set_tablefunc_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
Relids required_outer;
/*
* We don't support pushing join clauses into the quals of a tablefunc
* scan, but it could still have required parameterization due to LATERAL
* refs in the function expression.
*/
required_outer = rel->lateral_relids;
/* Generate appropriate path */
add_path(rel, create_tablefuncscan_path(root, rel,
required_outer));
}
/*
* set_cte_pathlist
* Build the (single) access path for a non-self-reference CTE RTE
*
* There's no need for a separate set_cte_size phase, since we don't
* support join-qual-parameterized paths for CTEs.
*/
static void
set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
Plan *cteplan;
PlannerInfo *cteroot;
Index levelsup;
int ndx;
ListCell *lc;
int plan_id;
Relids required_outer;
/*
* Find the referenced CTE, and locate the plan previously made for it.
*/
levelsup = rte->ctelevelsup;
cteroot = root;
while (levelsup-- > 0)
{
cteroot = cteroot->parent_root;
if (!cteroot) /* shouldn't happen */
elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
}
/*
* Note: cte_plan_ids can be shorter than cteList, if we are still working
* on planning the CTEs (ie, this is a side-reference from another CTE).
* So we mustn't use forboth here.
*/
ndx = 0;
foreach(lc, cteroot->parse->cteList)
{
CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
if (strcmp(cte->ctename, rte->ctename) == 0)
break;
ndx++;
}
if (lc == NULL) /* shouldn't happen */
elog(ERROR, "could not find CTE \"%s\"", rte->ctename);
if (ndx >= list_length(cteroot->cte_plan_ids))
elog(ERROR, "could not find plan for CTE \"%s\"", rte->ctename);
plan_id = list_nth_int(cteroot->cte_plan_ids, ndx);
if (plan_id <= 0)
elog(ERROR, "no plan was made for CTE \"%s\"", rte->ctename);
cteplan = (Plan *) list_nth(root->glob->subplans, plan_id - 1);
/* Mark rel with estimated output rows, width, etc */
set_cte_size_estimates(root, rel, cteplan->plan_rows);
/*
* We don't support pushing join clauses into the quals of a CTE scan, but
* it could still have required parameterization due to LATERAL refs in
* its tlist.
*/
required_outer = rel->lateral_relids;
/* Generate appropriate path */
add_path(rel, create_ctescan_path(root, rel, required_outer));
}
/*
* set_namedtuplestore_pathlist
* Build the (single) access path for a named tuplestore RTE
*
* There's no need for a separate set_namedtuplestore_size phase, since we
* don't support join-qual-parameterized paths for tuplestores.
*/
static void
set_namedtuplestore_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte)
{
Relids required_outer;
/* Mark rel with estimated output rows, width, etc */
set_namedtuplestore_size_estimates(root, rel);
/*
* We don't support pushing join clauses into the quals of a tuplestore
* scan, but it could still have required parameterization due to LATERAL
* refs in its tlist.
*/
required_outer = rel->lateral_relids;
/* Generate appropriate path */
add_path(rel, create_namedtuplestorescan_path(root, rel, required_outer));
/* Select cheapest path (pretty easy in this case...) */
set_cheapest(rel);
}
/*
* set_result_pathlist
* Build the (single) access path for an RTE_RESULT RTE
*
* There's no need for a separate set_result_size phase, since we
* don't support join-qual-parameterized paths for these RTEs.
*/
static void
set_result_pathlist(PlannerInfo *root, RelOptInfo *rel,
RangeTblEntry *rte)
{
Relids required_outer;
/* Mark rel with estimated output rows, width, etc */
set_result_size_estimates(root, rel);
/*
* We don't support pushing join clauses into the quals of a Result scan,
* but it could still have required parameterization due to LATERAL refs
* in its tlist.
*/
required_outer = rel->lateral_relids;
/* Generate appropriate path */
add_path(rel, create_resultscan_path(root, rel, required_outer));
/* Select cheapest path (pretty easy in this case...) */
set_cheapest(rel);
}
/*
* set_worktable_pathlist
* Build the (single) access path for a self-reference CTE RTE
*
* There's no need for a separate set_worktable_size phase, since we don't
* support join-qual-parameterized paths for CTEs.
*/
static void
set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
Path *ctepath;
PlannerInfo *cteroot;
Index levelsup;
Relids required_outer;
/*
* We need to find the non-recursive term's path, which is in the plan
* level that's processing the recursive UNION, which is one level *below*
* where the CTE comes from.
*/
levelsup = rte->ctelevelsup;
if (levelsup == 0) /* shouldn't happen */
elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
levelsup--;
cteroot = root;
while (levelsup-- > 0)
{
cteroot = cteroot->parent_root;
if (!cteroot) /* shouldn't happen */
elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
}
ctepath = cteroot->non_recursive_path;
if (!ctepath) /* shouldn't happen */
elog(ERROR, "could not find path for CTE \"%s\"", rte->ctename);
/* Mark rel with estimated output rows, width, etc */
set_cte_size_estimates(root, rel, ctepath->rows);
/*
* We don't support pushing join clauses into the quals of a worktable
* scan, but it could still have required parameterization due to LATERAL
* refs in its tlist. (I'm not sure this is actually possible given the
* restrictions on recursive references, but it's easy enough to support.)
*/
required_outer = rel->lateral_relids;
/* Generate appropriate path */
add_path(rel, create_worktablescan_path(root, rel, required_outer));
}
/*
* generate_gather_paths
* Generate parallel access paths for a relation by pushing a Gather or
* Gather Merge on top of a partial path.
*
* This must not be called until after we're done creating all partial paths
* for the specified relation. (Otherwise, add_partial_path might delete a
* path that some GatherPath or GatherMergePath has a reference to.)
*
* If we're generating paths for a scan or join relation, override_rows will
* be false, and we'll just use the relation's size estimate. When we're
* being called for a partially-grouped path, though, we need to override
* the rowcount estimate. (It's not clear that the particular value we're
* using here is actually best, but the underlying rel has no estimate so
* we must do something.)
*/
void
generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
{
Path *cheapest_partial_path;
Path *simple_gather_path;
ListCell *lc;
double rows;
double *rowsp = NULL;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
/*
* The output of Gather is always unsorted, so there's only one partial
* path of interest: the cheapest one. That will be the one at the front
* of partial_pathlist because of the way add_partial_path works.
*/
cheapest_partial_path = linitial(rel->partial_pathlist);
rows =
cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
simple_gather_path = (Path *)
create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
NULL, rowsp);
add_path(rel, simple_gather_path);
/*
* For each useful ordering, we can consider an order-preserving Gather
* Merge.
*/
foreach(lc, rel->partial_pathlist)
{
Path *subpath = (Path *) lfirst(lc);
GatherMergePath *path;
if (subpath->pathkeys == NIL)
continue;
rows = subpath->rows * subpath->parallel_workers;
path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
subpath->pathkeys, NULL, rowsp);
add_path(rel, &path->path);
}
}
/*
* get_useful_pathkeys_for_relation
* Determine which orderings of a relation might be useful.
*
* Getting data in sorted order can be useful either because the requested
* order matches the final output ordering for the overall query we're
* planning, or because it enables an efficient merge join. Here, we try
* to figure out which pathkeys to consider.
*
* This allows us to do incremental sort on top of an index scan under a gather
* merge node, i.e. parallelized.
*
* If the require_parallel_safe is true, we also require the expressions to
* be parallel safe (which allows pushing the sort below Gather Merge).
*
* XXX At the moment this can only ever return a list with a single element,
* because it looks at query_pathkeys only. So we might return the pathkeys
* directly, but it seems plausible we'll want to consider other orderings
* in the future. For example, we might want to consider pathkeys useful for
* merge joins.
*/
static List *
get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel,
bool require_parallel_safe)
{
List *useful_pathkeys_list = NIL;
/*
* Considering query_pathkeys is always worth it, because it might allow
* us to avoid a total sort when we have a partially presorted path
* available or to push the total sort into the parallel portion of the
* query.
*/
if (root->query_pathkeys)
{
ListCell *lc;
int npathkeys = 0; /* useful pathkeys */
foreach(lc, root->query_pathkeys)
{
PathKey *pathkey = (PathKey *) lfirst(lc);
EquivalenceClass *pathkey_ec = pathkey->pk_eclass;
/*
* We can only build a sort for pathkeys that contain a
* safe-to-compute-early EC member computable from the current
* relation's reltarget, so ignore the remainder of the list as
* soon as we find a pathkey without such a member.
*
* It's still worthwhile to return any prefix of the pathkeys list
* that meets this requirement, as we may be able to do an
* incremental sort.
*
* If requested, ensure the sort expression is parallel-safe too.
*/
if (!relation_can_be_sorted_early(root, rel, pathkey_ec,
require_parallel_safe))
break;
npathkeys++;
}
/*
* The whole query_pathkeys list matches, so append it directly, to
* allow comparing pathkeys easily by comparing list pointer. If we
* have to truncate the pathkeys, we gotta do a copy though.
*/
if (npathkeys == list_length(root->query_pathkeys))
useful_pathkeys_list = lappend(useful_pathkeys_list,
root->query_pathkeys);
else if (npathkeys > 0)
useful_pathkeys_list = lappend(useful_pathkeys_list,
list_copy_head(root->query_pathkeys,
npathkeys));
}
return useful_pathkeys_list;
}
/*
* generate_useful_gather_paths
* Generate parallel access paths for a relation by pushing a Gather or
* Gather Merge on top of a partial path.
*
* Unlike plain generate_gather_paths, this looks both at pathkeys of input
* paths (aiming to preserve the ordering), but also considers ordering that
* might be useful for nodes above the gather merge node, and tries to add
* a sort (regular or incremental) to provide that.
*/
void
generate_useful_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
{
ListCell *lc;
double rows;
double *rowsp = NULL;
List *useful_pathkeys_list = NIL;
Path *cheapest_partial_path = NULL;
/* If there are no partial paths, there's nothing to do here. */
if (rel->partial_pathlist == NIL)
return;
/* Should we override the rel's rowcount estimate? */
if (override_rows)
rowsp = &rows;
/* generate the regular gather (merge) paths */
generate_gather_paths(root, rel, override_rows);
/* consider incremental sort for interesting orderings */
useful_pathkeys_list = get_useful_pathkeys_for_relation(root, rel, true);
/* used for explicit (full) sort paths */
cheapest_partial_path = linitial(rel->partial_pathlist);
/*
* Consider sorted paths for each interesting ordering. We generate both
* incremental and full sort.
*/
foreach(lc, useful_pathkeys_list)
{
List *useful_pathkeys = lfirst(lc);
ListCell *lc2;
bool is_sorted;
int presorted_keys;
foreach(lc2, rel->partial_pathlist)
{
Path *subpath = (Path *) lfirst(lc2);
GatherMergePath *path;
is_sorted = pathkeys_count_contained_in(useful_pathkeys,
subpath->pathkeys,
&presorted_keys);
/*
* We don't need to consider the case where a subpath is already
* fully sorted because generate_gather_paths already creates a
* gather merge path for every subpath that has pathkeys present.
*
* But since the subpath is already sorted, we know we don't need
* to consider adding a sort (full or incremental) on top of it,
* so we can continue here.
*/
if (is_sorted)
continue;
/*
* Try at least sorting the cheapest path and also try
* incrementally sorting any path which is partially sorted
* already (no need to deal with paths which have presorted keys
* when incremental sort is disabled unless it's the cheapest
* input path).
*/
if (subpath != cheapest_partial_path &&
(presorted_keys == 0 || !enable_incremental_sort))
continue;
/*
* Consider regular sort for any path that's not presorted or if
* incremental sort is disabled. We've no need to consider both
* sort and incremental sort on the same path. We assume that
* incremental sort is always faster when there are presorted
* keys.
*
* This is not redundant with the gather paths created in
* generate_gather_paths, because that doesn't generate ordered
* output. Here we add an explicit sort to match the useful
* ordering.
*/
if (presorted_keys == 0 || !enable_incremental_sort)
{
subpath = (Path *) create_sort_path(root,
rel,
subpath,
useful_pathkeys,
-1.0);
rows = subpath->rows * subpath->parallel_workers;
}
else
subpath = (Path *) create_incremental_sort_path(root,
rel,
subpath,
useful_pathkeys,
presorted_keys,
-1);
path = create_gather_merge_path(root, rel,
subpath,
rel->reltarget,
subpath->pathkeys,
NULL,
rowsp);
add_path(rel, &path->path);
}
}
}
/*
* make_rel_from_joinlist
* Build access paths using a "joinlist" to guide the join path search.
*
* See comments for deconstruct_jointree() for definition of the joinlist
* data structure.
*/
static RelOptInfo *
make_rel_from_joinlist(PlannerInfo *root, List *joinlist)
{
int levels_needed;
List *initial_rels;
ListCell *jl;
/*
* Count the number of child joinlist nodes. This is the depth of the
* dynamic-programming algorithm we must employ to consider all ways of
* joining the child nodes.
*/
levels_needed = list_length(joinlist);
if (levels_needed <= 0)
return NULL; /* nothing to do? */
/*
* Construct a list of rels corresponding to the child joinlist nodes.
* This may contain both base rels and rels constructed according to
* sub-joinlists.
*/
initial_rels = NIL;
foreach(jl, joinlist)
{
Node *jlnode = (Node *) lfirst(jl);
RelOptInfo *thisrel;
if (IsA(jlnode, RangeTblRef))
{
int varno = ((RangeTblRef *) jlnode)->rtindex;
thisrel = find_base_rel(root, varno);
}
else if (IsA(jlnode, List))
{
/* Recurse to handle subproblem */
thisrel = make_rel_from_joinlist(root, (List *) jlnode);
}
else
{
elog(ERROR, "unrecognized joinlist node type: %d",
(int) nodeTag(jlnode));
thisrel = NULL; /* keep compiler quiet */
}
initial_rels = lappend(initial_rels, thisrel);
}
if (levels_needed == 1)
{
/*
* Single joinlist node, so we're done.
*/
return (RelOptInfo *) linitial(initial_rels);
}
else
{
/*
* Consider the different orders in which we could join the rels,
* using a plugin, GEQO, or the regular join search code.
*
* We put the initial_rels list into a PlannerInfo field because
* has_legal_joinclause() needs to look at it (ugly :-().
*/
root->initial_rels = initial_rels;
if (join_search_hook)
return (*join_search_hook) (root, levels_needed, initial_rels);
else if (enable_geqo && levels_needed >= geqo_threshold)
return geqo(root, levels_needed, initial_rels);
else
return standard_join_search(root, levels_needed, initial_rels);
}
}
/*
* standard_join_search
* Find possible joinpaths for a query by successively finding ways
* to join component relations into join relations.
*
* 'levels_needed' is the number of iterations needed, ie, the number of
* independent jointree items in the query. This is > 1.
*
* 'initial_rels' is a list of RelOptInfo nodes for each independent
* jointree item. These are the components to be joined together.
* Note that levels_needed == list_length(initial_rels).
*
* Returns the final level of join relations, i.e., the relation that is
* the result of joining all the original relations together.
* At least one implementation path must be provided for this relation and
* all required sub-relations.
*
* To support loadable plugins that modify planner behavior by changing the
* join searching algorithm, we provide a hook variable that lets a plugin
* replace or supplement this function. Any such hook must return the same
* final join relation as the standard code would, but it might have a
* different set of implementation paths attached, and only the sub-joinrels
* needed for these paths need have been instantiated.
*
* Note to plugin authors: the functions invoked during standard_join_search()
* modify root->join_rel_list and root->join_rel_hash. If you want to do more
* than one join-order search, you'll probably need to save and restore the
* original states of those data structures. See geqo_eval() for an example.
*/
RelOptInfo *
standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
{
int lev;
RelOptInfo *rel;
/*
* This function cannot be invoked recursively within any one planning
* problem, so join_rel_level[] can't be in use already.
*/
Assert(root->join_rel_level == NULL);
/*
* We employ a simple "dynamic programming" algorithm: we first find all
* ways to build joins of two jointree items, then all ways to build joins
* of three items (from two-item joins and single items), then four-item
* joins, and so on until we have considered all ways to join all the
* items into one rel.
*
* root->join_rel_level[j] is a list of all the j-item rels. Initially we
* set root->join_rel_level[1] to represent all the single-jointree-item
* relations.
*/
root->join_rel_level = (List **) palloc0((levels_needed + 1) * sizeof(List *));
root->join_rel_level[1] = initial_rels;
for (lev = 2; lev <= levels_needed; lev++)
{
ListCell *lc;
/*
* Determine all possible pairs of relations to be joined at this
* level, and build paths for making each one from every available
* pair of lower-level relations.
*/
join_search_one_level(root, lev);
/*
* Run generate_partitionwise_join_paths() and
* generate_useful_gather_paths() for each just-processed joinrel. We
* could not do this earlier because both regular and partial paths
* can get added to a particular joinrel at multiple times within
* join_search_one_level.
*
* After that, we're done creating paths for the joinrel, so run
* set_cheapest().
*/
foreach(lc, root->join_rel_level[lev])
{
rel = (RelOptInfo *) lfirst(lc);
/* Create paths for partitionwise joins. */
generate_partitionwise_join_paths(root, rel);
/*
* Except for the topmost scan/join rel, consider gathering
* partial paths. We'll do the same for the topmost scan/join rel
* once we know the final targetlist (see grouping_planner).
*/
if (!bms_equal(rel->relids, root->all_query_rels))
generate_useful_gather_paths(root, rel, false);
/* Find and save the cheapest paths for this rel */
set_cheapest(rel);
#ifdef OPTIMIZER_DEBUG
debug_print_rel(root, rel);
#endif
}
}
/*
* We should have a single rel at the final level.
*/
if (root->join_rel_level[levels_needed] == NIL)
elog(ERROR, "failed to build any %d-way joins", levels_needed);
Assert(list_length(root->join_rel_level[levels_needed]) == 1);
rel = (RelOptInfo *) linitial(root->join_rel_level[levels_needed]);
root->join_rel_level = NULL;
return rel;
}
/*****************************************************************************
* PUSHING QUALS DOWN INTO SUBQUERIES
*****************************************************************************/
/*
* subquery_is_pushdown_safe - is a subquery safe for pushing down quals?
*
* subquery is the particular component query being checked. topquery
* is the top component of a set-operations tree (the same Query if no
* set-op is involved).
*
* Conditions checked here:
*
* 1. If the subquery has a LIMIT clause, we must not push down any quals,
* since that could change the set of rows returned.
*
* 2. If the subquery contains EXCEPT or EXCEPT ALL set ops we cannot push
* quals into it, because that could change the results.
*
* 3. If the subquery uses DISTINCT, we cannot push volatile quals into it.
* This is because upper-level quals should semantically be evaluated only
* once per distinct row, not once per original row, and if the qual is
* volatile then extra evaluations could change the results. (This issue
* does not apply to other forms of aggregation such as GROUP BY, because
* when those are present we push into HAVING not WHERE, so that the quals
* are still applied after aggregation.)
*
* 4. If the subquery contains window functions, we cannot push volatile quals
* into it. The issue here is a bit different from DISTINCT: a volatile qual
* might succeed for some rows of a window partition and fail for others,
* thereby changing the partition contents and thus the window functions'
* results for rows that remain.
*
* 5. If the subquery contains any set-returning functions in its targetlist,
* we cannot push volatile quals into it. That would push them below the SRFs
* and thereby change the number of times they are evaluated. Also, a
* volatile qual could succeed for some SRF output rows and fail for others,
* a behavior that cannot occur if it's evaluated before SRF expansion.
*
* 6. If the subquery has nonempty grouping sets, we cannot push down any
* quals. The concern here is that a qual referencing a "constant" grouping
* column could get constant-folded, which would be improper because the value
* is potentially nullable by grouping-set expansion. This restriction could
* be removed if we had a parsetree representation that shows that such
* grouping columns are not really constant. (There are other ideas that
* could be used to relax this restriction, but that's the approach most
* likely to get taken in the future. Note that there's not much to be gained
* so long as subquery_planner can't move HAVING clauses to WHERE within such
* a subquery.)
*
* In addition, we make several checks on the subquery's output columns to see
* if it is safe to reference them in pushed-down quals. If output column k
* is found to be unsafe to reference, we set the reason for that inside
* safetyInfo->unsafeFlags[k], but we don't reject the subquery overall since
* column k might not be referenced by some/all quals. The unsafeFlags[]
* array will be consulted later by qual_is_pushdown_safe(). It's better to
* do it this way than to make the checks directly in qual_is_pushdown_safe(),
* because when the subquery involves set operations we have to check the
* output expressions in each arm of the set op.
*
* Note: pushing quals into a DISTINCT subquery is theoretically dubious:
* we're effectively assuming that the quals cannot distinguish values that
* the DISTINCT's equality operator sees as equal, yet there are many
* counterexamples to that assumption. However use of such a qual with a
* DISTINCT subquery would be unsafe anyway, since there's no guarantee which
* "equal" value will be chosen as the output value by the DISTINCT operation.
* So we don't worry too much about that. Another objection is that if the
* qual is expensive to evaluate, running it for each original row might cost
* more than we save by eliminating rows before the DISTINCT step. But it
* would be very hard to estimate that at this stage, and in practice pushdown
* seldom seems to make things worse, so we ignore that problem too.
*
* Note: likewise, pushing quals into a subquery with window functions is a
* bit dubious: the quals might remove some rows of a window partition while
* leaving others, causing changes in the window functions' results for the
* surviving rows. We insist that such a qual reference only partitioning
* columns, but again that only protects us if the qual does not distinguish
* values that the partitioning equality operator sees as equal. The risks
* here are perhaps larger than for DISTINCT, since no de-duplication of rows
* occurs and thus there is no theoretical problem with such a qual. But
* we'll do this anyway because the potential performance benefits are very
* large, and we've seen no field complaints about the longstanding comparable
* behavior with DISTINCT.
*/
static bool
subquery_is_pushdown_safe(Query *subquery, Query *topquery,
pushdown_safety_info *safetyInfo)
{
SetOperationStmt *topop;
/* Check point 1 */
if (subquery->limitOffset != NULL || subquery->limitCount != NULL)
return false;
/* Check point 6 */
if (subquery->groupClause && subquery->groupingSets)
return false;
/* Check points 3, 4, and 5 */
if (subquery->distinctClause ||
subquery->hasWindowFuncs ||
subquery->hasTargetSRFs)
safetyInfo->unsafeVolatile = true;
/*
* If we're at a leaf query, check for unsafe expressions in its target
* list, and mark any reasons why they're unsafe in unsafeFlags[].
* (Non-leaf nodes in setop trees have only simple Vars in their tlists,
* so no need to check them.)
*/
if (subquery->setOperations == NULL)
check_output_expressions(subquery, safetyInfo);
/* Are we at top level, or looking at a setop component? */
if (subquery == topquery)
{
/* Top level, so check any component queries */
if (subquery->setOperations != NULL)
if (!recurse_pushdown_safe(subquery->setOperations, topquery,
safetyInfo))
return false;
}
else
{
/* Setop component must not have more components (too weird) */
if (subquery->setOperations != NULL)
return false;
/* Check whether setop component output types match top level */
topop = castNode(SetOperationStmt, topquery->setOperations);
Assert(topop);
compare_tlist_datatypes(subquery->targetList,
topop->colTypes,
safetyInfo);
}
return true;
}
/*
* Helper routine to recurse through setOperations tree
*/
static bool
recurse_pushdown_safe(Node *setOp, Query *topquery,
pushdown_safety_info *safetyInfo)
{
if (IsA(setOp, RangeTblRef))
{
RangeTblRef *rtr = (RangeTblRef *) setOp;
RangeTblEntry *rte = rt_fetch(rtr->rtindex, topquery->rtable);
Query *subquery = rte->subquery;
Assert(subquery != NULL);
return subquery_is_pushdown_safe(subquery, topquery, safetyInfo);
}
else if (IsA(setOp, SetOperationStmt))
{
SetOperationStmt *op = (SetOperationStmt *) setOp;
/* EXCEPT is no good (point 2 for subquery_is_pushdown_safe) */
if (op->op == SETOP_EXCEPT)
return false;
/* Else recurse */
if (!recurse_pushdown_safe(op->larg, topquery, safetyInfo))
return false;
if (!recurse_pushdown_safe(op->rarg, topquery, safetyInfo))
return false;
}
else
{
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(setOp));
}
return true;
}
/*
* check_output_expressions - check subquery's output expressions for safety
*
* There are several cases in which it's unsafe to push down an upper-level
* qual if it references a particular output column of a subquery. We check
* each output column of the subquery and set flags in unsafeFlags[k] when we
* see that column is unsafe for a pushed-down qual to reference. The
* conditions checked here are:
*
* 1. We must not push down any quals that refer to subselect outputs that
* return sets, else we'd introduce functions-returning-sets into the
* subquery's WHERE/HAVING quals.
*
* 2. We must not push down any quals that refer to subselect outputs that
* contain volatile functions, for fear of introducing strange results due
* to multiple evaluation of a volatile function.
*
* 3. If the subquery uses DISTINCT ON, we must not push down any quals that
* refer to non-DISTINCT output columns, because that could change the set
* of rows returned. (This condition is vacuous for DISTINCT, because then
* there are no non-DISTINCT output columns, so we needn't check. Note that
* subquery_is_pushdown_safe already reported that we can't use volatile
* quals if there's DISTINCT or DISTINCT ON.)
*
* 4. If the subquery has any window functions, we must not push down quals
* that reference any output columns that are not listed in all the subquery's
* window PARTITION BY clauses. We can push down quals that use only
* partitioning columns because they should succeed or fail identically for
* every row of any one window partition, and totally excluding some
* partitions will not change a window function's results for remaining
* partitions. (Again, this also requires nonvolatile quals, but
* subquery_is_pushdown_safe handles that.). Subquery columns marked as
* unsafe for this reason can still have WindowClause run conditions pushed
* down.
*/
static void
check_output_expressions(Query *subquery, pushdown_safety_info *safetyInfo)
{
ListCell *lc;
foreach(lc, subquery->targetList)
{
TargetEntry *tle = (TargetEntry *) lfirst(lc);
if (tle->resjunk)
continue; /* ignore resjunk columns */
/* Functions returning sets are unsafe (point 1) */
if (subquery->hasTargetSRFs &&
(safetyInfo->unsafeFlags[tle->resno] &
UNSAFE_HAS_SET_FUNC) == 0 &&
expression_returns_set((Node *) tle->expr))
{
safetyInfo->unsafeFlags[tle->resno] |= UNSAFE_HAS_SET_FUNC;
continue;
}
/* Volatile functions are unsafe (point 2) */
if ((safetyInfo->unsafeFlags[tle->resno] &
UNSAFE_HAS_VOLATILE_FUNC) == 0 &&
contain_volatile_functions((Node *) tle->expr))
{
safetyInfo->unsafeFlags[tle->resno] |= UNSAFE_HAS_VOLATILE_FUNC;
continue;
}
/* If subquery uses DISTINCT ON, check point 3 */
if (subquery->hasDistinctOn &&
(safetyInfo->unsafeFlags[tle->resno] &
UNSAFE_NOTIN_DISTINCTON_CLAUSE) == 0 &&
!targetIsInSortList(tle, InvalidOid, subquery->distinctClause))
{
/* non-DISTINCT column, so mark it unsafe */
safetyInfo->unsafeFlags[tle->resno] |= UNSAFE_NOTIN_DISTINCTON_CLAUSE;
continue;
}
/* If subquery uses window functions, check point 4 */
if (subquery->hasWindowFuncs &&
(safetyInfo->unsafeFlags[tle->resno] &
UNSAFE_NOTIN_DISTINCTON_CLAUSE) == 0 &&
!targetIsInAllPartitionLists(tle, subquery))
{
/* not present in all PARTITION BY clauses, so mark it unsafe */
safetyInfo->unsafeFlags[tle->resno] |= UNSAFE_NOTIN_PARTITIONBY_CLAUSE;
continue;
}
}
}
/*
* For subqueries using UNION/UNION ALL/INTERSECT/INTERSECT ALL, we can
* push quals into each component query, but the quals can only reference
* subquery columns that suffer no type coercions in the set operation.
* Otherwise there are possible semantic gotchas. So, we check the
* component queries to see if any of them have output types different from
* the top-level setop outputs. We set the UNSAFE_TYPE_MISMATCH bit in
* unsafeFlags[k] if column k has different type in any component.
*
* We don't have to care about typmods here: the only allowed difference
* between set-op input and output typmods is input is a specific typmod
* and output is -1, and that does not require a coercion.
*
* tlist is a subquery tlist.
* colTypes is an OID list of the top-level setop's output column types.
* safetyInfo is the pushdown_safety_info to set unsafeFlags[] for.
*/
static void
compare_tlist_datatypes(List *tlist, List *colTypes,
pushdown_safety_info *safetyInfo)
{
ListCell *l;
ListCell *colType = list_head(colTypes);
foreach(l, tlist)
{
TargetEntry *tle = (TargetEntry *) lfirst(l);
if (tle->resjunk)
continue; /* ignore resjunk columns */
if (colType == NULL)
elog(ERROR, "wrong number of tlist entries");
if (exprType((Node *) tle->expr) != lfirst_oid(colType))
safetyInfo->unsafeFlags[tle->resno] |= UNSAFE_TYPE_MISMATCH;
colType = lnext(colTypes, colType);
}
if (colType != NULL)
elog(ERROR, "wrong number of tlist entries");
}
/*
* targetIsInAllPartitionLists
* True if the TargetEntry is listed in the PARTITION BY clause
* of every window defined in the query.
*
* It would be safe to ignore windows not actually used by any window
* function, but it's not easy to get that info at this stage; and it's
* unlikely to be useful to spend any extra cycles getting it, since
* unreferenced window definitions are probably infrequent in practice.
*/
static bool
targetIsInAllPartitionLists(TargetEntry *tle, Query *query)
{
ListCell *lc;
foreach(lc, query->windowClause)
{
WindowClause *wc = (WindowClause *) lfirst(lc);
if (!targetIsInSortList(tle, InvalidOid, wc->partitionClause))
return false;
}
return true;
}
/*
* qual_is_pushdown_safe - is a particular rinfo safe to push down?
*
* rinfo is a restriction clause applying to the given subquery (whose RTE
* has index rti in the parent query).
*
* Conditions checked here:
*
* 1. rinfo's clause must not contain any SubPlans (mainly because it's
* unclear that it will work correctly: SubLinks will already have been
* transformed into SubPlans in the qual, but not in the subquery). Note that
* SubLinks that transform to initplans are safe, and will be accepted here
* because what we'll see in the qual is just a Param referencing the initplan
* output.
*
* 2. If unsafeVolatile is set, rinfo's clause must not contain any volatile
* functions.
*
* 3. If unsafeLeaky is set, rinfo's clause must not contain any leaky
* functions that are passed Var nodes, and therefore might reveal values from
* the subquery as side effects.
*
* 4. rinfo's clause must not refer to the whole-row output of the subquery
* (since there is no easy way to name that within the subquery itself).
*
* 5. rinfo's clause must not refer to any subquery output columns that were
* found to be unsafe to reference by subquery_is_pushdown_safe().
*/
static pushdown_safe_type
qual_is_pushdown_safe(Query *subquery, Index rti, RestrictInfo *rinfo,
pushdown_safety_info *safetyInfo)
{
pushdown_safe_type safe = PUSHDOWN_SAFE;
Node *qual = (Node *) rinfo->clause;
List *vars;
ListCell *vl;
/* Refuse subselects (point 1) */
if (contain_subplans(qual))
return PUSHDOWN_UNSAFE;
/* Refuse volatile quals if we found they'd be unsafe (point 2) */
if (safetyInfo->unsafeVolatile &&
contain_volatile_functions((Node *) rinfo))
return PUSHDOWN_UNSAFE;
/* Refuse leaky quals if told to (point 3) */
if (safetyInfo->unsafeLeaky &&
contain_leaked_vars(qual))
return PUSHDOWN_UNSAFE;
/*
* Examine all Vars used in clause. Since it's a restriction clause, all
* such Vars must refer to subselect output columns ... unless this is
* part of a LATERAL subquery, in which case there could be lateral
* references.
*
* By omitting the relevant flags, this also gives us a cheap sanity check
* that no aggregates or window functions appear in the qual. Those would
* be unsafe to push down, but at least for the moment we could never see
* any in a qual anyhow.
*/
vars = pull_var_clause(qual, PVC_INCLUDE_PLACEHOLDERS);
foreach(vl, vars)
{
Var *var = (Var *) lfirst(vl);
/*
* XXX Punt if we find any PlaceHolderVars in the restriction clause.
* It's not clear whether a PHV could safely be pushed down, and even
* less clear whether such a situation could arise in any cases of
* practical interest anyway. So for the moment, just refuse to push
* down.
*/
if (!IsA(var, Var))
{
safe = PUSHDOWN_UNSAFE;
break;
}
/*
* Punt if we find any lateral references. It would be safe to push
* these down, but we'd have to convert them into outer references,
* which subquery_push_qual lacks the infrastructure to do. The case
* arises so seldom that it doesn't seem worth working hard on.
*/
if (var->varno != rti)
{
safe = PUSHDOWN_UNSAFE;
break;
}
/* Subqueries have no system columns */
Assert(var->varattno >= 0);
/* Check point 4 */
if (var->varattno == 0)
{
safe = PUSHDOWN_UNSAFE;
break;
}
/* Check point 5 */
if (safetyInfo->unsafeFlags[var->varattno] != 0)
{
if (safetyInfo->unsafeFlags[var->varattno] &
(UNSAFE_HAS_VOLATILE_FUNC | UNSAFE_HAS_SET_FUNC |
UNSAFE_NOTIN_DISTINCTON_CLAUSE | UNSAFE_TYPE_MISMATCH))
{
safe = PUSHDOWN_UNSAFE;
break;
}
else
{
/* UNSAFE_NOTIN_PARTITIONBY_CLAUSE is ok for run conditions */
safe = PUSHDOWN_WINDOWCLAUSE_RUNCOND;
/* don't break, we might find another Var that's unsafe */
}
}
}
list_free(vars);
return safe;
}
/*
* subquery_push_qual - push down a qual that we have determined is safe
*/
static void
subquery_push_qual(Query *subquery, RangeTblEntry *rte, Index rti, Node *qual)
{
if (subquery->setOperations != NULL)
{
/* Recurse to push it separately to each component query */
recurse_push_qual(subquery->setOperations, subquery,
rte, rti, qual);
}
else
{
/*
* We need to replace Vars in the qual (which must refer to outputs of
* the subquery) with copies of the subquery's targetlist expressions.
* Note that at this point, any uplevel Vars in the qual should have
* been replaced with Params, so they need no work.
*
* This step also ensures that when we are pushing into a setop tree,
* each component query gets its own copy of the qual.
*/
qual = ReplaceVarsFromTargetList(qual, rti, 0, rte,
subquery->targetList,
REPLACEVARS_REPORT_ERROR, 0,
&subquery->hasSubLinks);
/*
* Now attach the qual to the proper place: normally WHERE, but if the
* subquery uses grouping or aggregation, put it in HAVING (since the
* qual really refers to the group-result rows).
*/
if (subquery->hasAggs || subquery->groupClause || subquery->groupingSets || subquery->havingQual)
subquery->havingQual = make_and_qual(subquery->havingQual, qual);
else
subquery->jointree->quals =
make_and_qual(subquery->jointree->quals, qual);
/*
* We need not change the subquery's hasAggs or hasSubLinks flags,
* since we can't be pushing down any aggregates that weren't there
* before, and we don't push down subselects at all.
*/
}
}
/*
* Helper routine to recurse through setOperations tree
*/
static void
recurse_push_qual(Node *setOp, Query *topquery,
RangeTblEntry *rte, Index rti, Node *qual)
{
if (IsA(setOp, RangeTblRef))
{
RangeTblRef *rtr = (RangeTblRef *) setOp;
RangeTblEntry *subrte = rt_fetch(rtr->rtindex, topquery->rtable);
Query *subquery = subrte->subquery;
Assert(subquery != NULL);
subquery_push_qual(subquery, rte, rti, qual);
}
else if (IsA(setOp, SetOperationStmt))
{
SetOperationStmt *op = (SetOperationStmt *) setOp;
recurse_push_qual(op->larg, topquery, rte, rti, qual);
recurse_push_qual(op->rarg, topquery, rte, rti, qual);
}
else
{
elog(ERROR, "unrecognized node type: %d",
(int) nodeTag(setOp));
}
}
/*****************************************************************************
* SIMPLIFYING SUBQUERY TARGETLISTS
*****************************************************************************/
/*
* remove_unused_subquery_outputs
* Remove subquery targetlist items we don't need
*
* It's possible, even likely, that the upper query does not read all the
* output columns of the subquery. We can remove any such outputs that are
* not needed by the subquery itself (e.g., as sort/group columns) and do not
* affect semantics otherwise (e.g., volatile functions can't be removed).
* This is useful not only because we might be able to remove expensive-to-
* compute expressions, but because deletion of output columns might allow
* optimizations such as join removal to occur within the subquery.
*
* extra_used_attrs can be passed as non-NULL to mark any columns (offset by
* FirstLowInvalidHeapAttributeNumber) that we should not remove. This
* parameter is modifed by the function, so callers must make a copy if they
* need to use the passed in Bitmapset after calling this function.
*
* To avoid affecting column numbering in the targetlist, we don't physically
* remove unused tlist entries, but rather replace their expressions with NULL
* constants. This is implemented by modifying subquery->targetList.
*/
static void
remove_unused_subquery_outputs(Query *subquery, RelOptInfo *rel,
Bitmapset *extra_used_attrs)
{
Bitmapset *attrs_used;
ListCell *lc;
/*
* Just point directly to extra_used_attrs. No need to bms_copy as none of
* the current callers use the Bitmapset after calling this function.
*/
attrs_used = extra_used_attrs;
/*
* Do nothing if subquery has UNION/INTERSECT/EXCEPT: in principle we
* could update all the child SELECTs' tlists, but it seems not worth the
* trouble presently.
*/
if (subquery->setOperations)
return;
/*
* If subquery has regular DISTINCT (not DISTINCT ON), we're wasting our
* time: all its output columns must be used in the distinctClause.
*/
if (subquery->distinctClause && !subquery->hasDistinctOn)
return;
/*
* Collect a bitmap of all the output column numbers used by the upper
* query.
*
* Add all the attributes needed for joins or final output. Note: we must
* look at rel's targetlist, not the attr_needed data, because attr_needed
* isn't computed for inheritance child rels, cf set_append_rel_size().
* (XXX might be worth changing that sometime.)
*/
pull_varattnos((Node *) rel->reltarget->exprs, rel->relid, &attrs_used);
/* Add all the attributes used by un-pushed-down restriction clauses. */
foreach(lc, rel->baserestrictinfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
pull_varattnos((Node *) rinfo->clause, rel->relid, &attrs_used);
}
/*
* If there's a whole-row reference to the subquery, we can't remove
* anything.
*/
if (bms_is_member(0 - FirstLowInvalidHeapAttributeNumber, attrs_used))
return;
/*
* Run through the tlist and zap entries we don't need. It's okay to
* modify the tlist items in-place because set_subquery_pathlist made a
* copy of the subquery.
*/
foreach(lc, subquery->targetList)
{
TargetEntry *tle = (TargetEntry *) lfirst(lc);
Node *texpr = (Node *) tle->expr;
/*
* If it has a sortgroupref number, it's used in some sort/group
* clause so we'd better not remove it. Also, don't remove any
* resjunk columns, since their reason for being has nothing to do
* with anybody reading the subquery's output. (It's likely that
* resjunk columns in a sub-SELECT would always have ressortgroupref
* set, but even if they don't, it seems imprudent to remove them.)
*/
if (tle->ressortgroupref || tle->resjunk)
continue;
/*
* If it's used by the upper query, we can't remove it.
*/
if (bms_is_member(tle->resno - FirstLowInvalidHeapAttributeNumber,
attrs_used))
continue;
/*
* If it contains a set-returning function, we can't remove it since
* that could change the number of rows returned by the subquery.
*/
if (subquery->hasTargetSRFs &&
expression_returns_set(texpr))
continue;
/*
* If it contains volatile functions, we daren't remove it for fear
* that the user is expecting their side-effects to happen.
*/
if (contain_volatile_functions(texpr))
continue;
/*
* OK, we don't need it. Replace the expression with a NULL constant.
* Preserve the exposed type of the expression, in case something
* looks at the rowtype of the subquery's result.
*/
tle->expr = (Expr *) makeNullConst(exprType(texpr),
exprTypmod(texpr),
exprCollation(texpr));
}
}
/*
* create_partial_bitmap_paths
* Build partial bitmap heap path for the relation
*/
void
create_partial_bitmap_paths(PlannerInfo *root, RelOptInfo *rel,
Path *bitmapqual)
{
int parallel_workers;
double pages_fetched;
/* Compute heap pages for bitmap heap scan */
pages_fetched = compute_bitmap_pages(root, rel, bitmapqual, 1.0,
NULL, NULL);
parallel_workers = compute_parallel_worker(rel, pages_fetched, -1,
max_parallel_workers_per_gather);
if (parallel_workers <= 0)
return;
add_partial_path(rel, (Path *) create_bitmap_heap_path(root, rel,
bitmapqual, rel->lateral_relids, 1.0, parallel_workers));
}
/*
* Compute the number of parallel workers that should be used to scan a
* relation. We compute the parallel workers based on the size of the heap to
* be scanned and the size of the index to be scanned, then choose a minimum
* of those.
*
* "heap_pages" is the number of pages from the table that we expect to scan, or
* -1 if we don't expect to scan any.
*
* "index_pages" is the number of pages from the index that we expect to scan, or
* -1 if we don't expect to scan any.
*
* "max_workers" is caller's limit on the number of workers. This typically
* comes from a GUC.
*/
int
compute_parallel_worker(RelOptInfo *rel, double heap_pages, double index_pages,
int max_workers)
{
int parallel_workers = 0;
/*
* If the user has set the parallel_workers reloption, use that; otherwise
* select a default number of workers.
*/
if (rel->rel_parallel_workers != -1)
parallel_workers = rel->rel_parallel_workers;
else
{
/*
* If the number of pages being scanned is insufficient to justify a
* parallel scan, just return zero ... unless it's an inheritance
* child. In that case, we want to generate a parallel path here
* anyway. It might not be worthwhile just for this relation, but
* when combined with all of its inheritance siblings it may well pay
* off.
*/
if (rel->reloptkind == RELOPT_BASEREL &&
((heap_pages >= 0 && heap_pages < min_parallel_table_scan_size) ||
(index_pages >= 0 && index_pages < min_parallel_index_scan_size)))
return 0;
if (heap_pages >= 0)
{
int heap_parallel_threshold;
int heap_parallel_workers = 1;
/*
* Select the number of workers based on the log of the size of
* the relation. This probably needs to be a good deal more
* sophisticated, but we need something here for now. Note that
* the upper limit of the min_parallel_table_scan_size GUC is
* chosen to prevent overflow here.
*/
heap_parallel_threshold = Max(min_parallel_table_scan_size, 1);
while (heap_pages >= (BlockNumber) (heap_parallel_threshold * 3))
{
heap_parallel_workers++;
heap_parallel_threshold *= 3;
if (heap_parallel_threshold > INT_MAX / 3)
break; /* avoid overflow */
}
parallel_workers = heap_parallel_workers;
}
if (index_pages >= 0)
{
int index_parallel_workers = 1;
int index_parallel_threshold;
/* same calculation as for heap_pages above */
index_parallel_threshold = Max(min_parallel_index_scan_size, 1);
while (index_pages >= (BlockNumber) (index_parallel_threshold * 3))
{
index_parallel_workers++;
index_parallel_threshold *= 3;
if (index_parallel_threshold > INT_MAX / 3)
break; /* avoid overflow */
}
if (parallel_workers > 0)
parallel_workers = Min(parallel_workers, index_parallel_workers);
else
parallel_workers = index_parallel_workers;
}
}
/* In no case use more than caller supplied maximum number of workers */
parallel_workers = Min(parallel_workers, max_workers);
return parallel_workers;
}
/*
* generate_partitionwise_join_paths
* Create paths representing partitionwise join for given partitioned
* join relation.
*
* This must not be called until after we are done adding paths for all
* child-joins. Otherwise, add_path might delete a path to which some path
* generated here has a reference.
*/
void
generate_partitionwise_join_paths(PlannerInfo *root, RelOptInfo *rel)
{
List *live_children = NIL;
int cnt_parts;
int num_parts;
RelOptInfo **part_rels;
/* Handle only join relations here. */
if (!IS_JOIN_REL(rel))
return;
/* We've nothing to do if the relation is not partitioned. */
if (!IS_PARTITIONED_REL(rel))
return;
/* The relation should have consider_partitionwise_join set. */
Assert(rel->consider_partitionwise_join);
/* Guard against stack overflow due to overly deep partition hierarchy. */
check_stack_depth();
num_parts = rel->nparts;
part_rels = rel->part_rels;
/* Collect non-dummy child-joins. */
for (cnt_parts = 0; cnt_parts < num_parts; cnt_parts++)
{
RelOptInfo *child_rel = part_rels[cnt_parts];
/* If it's been pruned entirely, it's certainly dummy. */
if (child_rel == NULL)
continue;
/* Make partitionwise join paths for this partitioned child-join. */
generate_partitionwise_join_paths(root, child_rel);
/* If we failed to make any path for this child, we must give up. */
if (child_rel->pathlist == NIL)
{
/*
* Mark the parent joinrel as unpartitioned so that later
* functions treat it correctly.
*/
rel->nparts = 0;
return;
}
/* Else, identify the cheapest path for it. */
set_cheapest(child_rel);
/* Dummy children need not be scanned, so ignore those. */
if (IS_DUMMY_REL(child_rel))
continue;
#ifdef OPTIMIZER_DEBUG
debug_print_rel(root, child_rel);
#endif
live_children = lappend(live_children, child_rel);
}
/* If all child-joins are dummy, parent join is also dummy. */
if (!live_children)
{
mark_dummy_rel(rel);
return;
}
/* Build additional paths for this rel from child-join paths. */
add_paths_to_append_rel(root, rel, live_children);
list_free(live_children);
}
/*****************************************************************************
* DEBUG SUPPORT
*****************************************************************************/
#ifdef OPTIMIZER_DEBUG
static void
print_relids(PlannerInfo *root, Relids relids)
{
int x;
bool first = true;
x = -1;
while ((x = bms_next_member(relids, x)) >= 0)
{
if (!first)
printf(" ");
if (x < root->simple_rel_array_size &&
root->simple_rte_array[x])
printf("%s", root->simple_rte_array[x]->eref->aliasname);
else
printf("%d", x);
first = false;
}
}
static void
print_restrictclauses(PlannerInfo *root, List *clauses)
{
ListCell *l;
foreach(l, clauses)
{
RestrictInfo *c = lfirst(l);
print_expr((Node *) c->clause, root->parse->rtable);
if (lnext(clauses, l))
printf(", ");
}
}
static void
print_path(PlannerInfo *root, Path *path, int indent)
{
const char *ptype;
bool join = false;
Path *subpath = NULL;
int i;
switch (nodeTag(path))
{
case T_Path:
switch (path->pathtype)
{
case T_SeqScan:
ptype = "SeqScan";
break;
case T_SampleScan:
ptype = "SampleScan";
break;
case T_FunctionScan:
ptype = "FunctionScan";
break;
case T_TableFuncScan:
ptype = "TableFuncScan";
break;
case T_ValuesScan:
ptype = "ValuesScan";
break;
case T_CteScan:
ptype = "CteScan";
break;
case T_NamedTuplestoreScan:
ptype = "NamedTuplestoreScan";
break;
case T_Result:
ptype = "Result";
break;
case T_WorkTableScan:
ptype = "WorkTableScan";
break;
default:
ptype = "???Path";
break;
}
break;
case T_IndexPath:
ptype = "IdxScan";
break;
case T_BitmapHeapPath:
ptype = "BitmapHeapScan";
break;
case T_BitmapAndPath:
ptype = "BitmapAndPath";
break;
case T_BitmapOrPath:
ptype = "BitmapOrPath";
break;
case T_TidPath:
ptype = "TidScan";
break;
case T_SubqueryScanPath:
ptype = "SubqueryScan";
break;
case T_ForeignPath:
ptype = "ForeignScan";
break;
case T_CustomPath:
ptype = "CustomScan";
break;
case T_NestPath:
ptype = "NestLoop";
join = true;
break;
case T_MergePath:
ptype = "MergeJoin";
join = true;
break;
case T_HashPath:
ptype = "HashJoin";
join = true;
break;
case T_AppendPath:
ptype = "Append";
break;
case T_MergeAppendPath:
ptype = "MergeAppend";
break;
case T_GroupResultPath:
ptype = "GroupResult";
break;
case T_MaterialPath:
ptype = "Material";
subpath = ((MaterialPath *) path)->subpath;
break;
case T_MemoizePath:
ptype = "Memoize";
subpath = ((MemoizePath *) path)->subpath;
break;
case T_UniquePath:
ptype = "Unique";
subpath = ((UniquePath *) path)->subpath;
break;
case T_GatherPath:
ptype = "Gather";
subpath = ((GatherPath *) path)->subpath;
break;
case T_GatherMergePath:
ptype = "GatherMerge";
subpath = ((GatherMergePath *) path)->subpath;
break;
case T_ProjectionPath:
ptype = "Projection";
subpath = ((ProjectionPath *) path)->subpath;
break;
case T_ProjectSetPath:
ptype = "ProjectSet";
subpath = ((ProjectSetPath *) path)->subpath;
break;
case T_SortPath:
ptype = "Sort";
subpath = ((SortPath *) path)->subpath;
break;
case T_IncrementalSortPath:
ptype = "IncrementalSort";
subpath = ((SortPath *) path)->subpath;
break;
case T_GroupPath:
ptype = "Group";
subpath = ((GroupPath *) path)->subpath;
break;
case T_UpperUniquePath:
ptype = "UpperUnique";
subpath = ((UpperUniquePath *) path)->subpath;
break;
case T_AggPath:
ptype = "Agg";
subpath = ((AggPath *) path)->subpath;
break;
case T_GroupingSetsPath:
ptype = "GroupingSets";
subpath = ((GroupingSetsPath *) path)->subpath;
break;
case T_MinMaxAggPath:
ptype = "MinMaxAgg";
break;
case T_WindowAggPath:
ptype = "WindowAgg";
subpath = ((WindowAggPath *) path)->subpath;
break;
case T_SetOpPath:
ptype = "SetOp";
subpath = ((SetOpPath *) path)->subpath;
break;
case T_RecursiveUnionPath:
ptype = "RecursiveUnion";
break;
case T_LockRowsPath:
ptype = "LockRows";
subpath = ((LockRowsPath *) path)->subpath;
break;
case T_ModifyTablePath:
ptype = "ModifyTable";
break;
case T_LimitPath:
ptype = "Limit";
subpath = ((LimitPath *) path)->subpath;
break;
default:
ptype = "???Path";
break;
}
for (i = 0; i < indent; i++)
printf("\t");
printf("%s", ptype);
if (path->parent)
{
printf("(");
print_relids(root, path->parent->relids);
printf(")");
}
if (path->param_info)
{
printf(" required_outer (");
print_relids(root, path->param_info->ppi_req_outer);
printf(")");
}
printf(" rows=%.0f cost=%.2f..%.2f\n",
path->rows, path->startup_cost, path->total_cost);
if (path->pathkeys)
{
for (i = 0; i < indent; i++)
printf("\t");
printf(" pathkeys: ");
print_pathkeys(path->pathkeys, root->parse->rtable);
}
if (join)
{
JoinPath *jp = (JoinPath *) path;
for (i = 0; i < indent; i++)
printf("\t");
printf(" clauses: ");
print_restrictclauses(root, jp->joinrestrictinfo);
printf("\n");
if (IsA(path, MergePath))
{
MergePath *mp = (MergePath *) path;
for (i = 0; i < indent; i++)
printf("\t");
printf(" sortouter=%d sortinner=%d materializeinner=%d\n",
((mp->outersortkeys) ? 1 : 0),
((mp->innersortkeys) ? 1 : 0),
((mp->materialize_inner) ? 1 : 0));
}
print_path(root, jp->outerjoinpath, indent + 1);
print_path(root, jp->innerjoinpath, indent + 1);
}
if (subpath)
print_path(root, subpath, indent + 1);
}
void
debug_print_rel(PlannerInfo *root, RelOptInfo *rel)
{
ListCell *l;
printf("RELOPTINFO (");
print_relids(root, rel->relids);
printf("): rows=%.0f width=%d\n", rel->rows, rel->reltarget->width);
if (rel->baserestrictinfo)
{
printf("\tbaserestrictinfo: ");
print_restrictclauses(root, rel->baserestrictinfo);
printf("\n");
}
if (rel->joininfo)
{
printf("\tjoininfo: ");
print_restrictclauses(root, rel->joininfo);
printf("\n");
}
printf("\tpath list:\n");
foreach(l, rel->pathlist)
print_path(root, lfirst(l), 1);
if (rel->cheapest_parameterized_paths)
{
printf("\n\tcheapest parameterized paths:\n");
foreach(l, rel->cheapest_parameterized_paths)
print_path(root, lfirst(l), 1);
}
if (rel->cheapest_startup_path)
{
printf("\n\tcheapest startup path:\n");
print_path(root, rel->cheapest_startup_path, 1);
}
if (rel->cheapest_total_path)
{
printf("\n\tcheapest total path:\n");
print_path(root, rel->cheapest_total_path, 1);
}
printf("\n");
fflush(stdout);
}
#endif /* OPTIMIZER_DEBUG */
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