/*-------------------------------------------------------------------------
*
* postgres_fdw.c
* Foreign-data wrapper for remote PostgreSQL servers
*
* Portions Copyright (c) 2012-2014, PostgreSQL Global Development Group
*
* IDENTIFICATION
* contrib/postgres_fdw/postgres_fdw.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "postgres_fdw.h"
#include "access/htup_details.h"
#include "access/sysattr.h"
#include "commands/defrem.h"
#include "commands/explain.h"
#include "commands/vacuum.h"
#include "foreign/fdwapi.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/cost.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/prep.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/var.h"
#include "parser/parsetree.h"
#include "utils/builtins.h"
#include "utils/guc.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
PG_MODULE_MAGIC;
/* Default CPU cost to start up a foreign query. */
#define DEFAULT_FDW_STARTUP_COST 100.0
/* Default CPU cost to process 1 row (above and beyond cpu_tuple_cost). */
#define DEFAULT_FDW_TUPLE_COST 0.01
/*
* FDW-specific planner information kept in RelOptInfo.fdw_private for a
* foreign table. This information is collected by postgresGetForeignRelSize.
*/
typedef struct PgFdwRelationInfo
{
/* baserestrictinfo clauses, broken down into safe and unsafe subsets. */
List *remote_conds;
List *local_conds;
/* Bitmap of attr numbers we need to fetch from the remote server. */
Bitmapset *attrs_used;
/* Cost and selectivity of local_conds. */
QualCost local_conds_cost;
Selectivity local_conds_sel;
/* Estimated size and cost for a scan with baserestrictinfo quals. */
double rows;
int width;
Cost startup_cost;
Cost total_cost;
/* Options extracted from catalogs. */
bool use_remote_estimate;
Cost fdw_startup_cost;
Cost fdw_tuple_cost;
/* Cached catalog information. */
ForeignTable *table;
ForeignServer *server;
UserMapping *user; /* only set in use_remote_estimate mode */
} PgFdwRelationInfo;
/*
* Indexes of FDW-private information stored in fdw_private lists.
*
* We store various information in ForeignScan.fdw_private to pass it from
* planner to executor. Currently we store:
*
* 1) SELECT statement text to be sent to the remote server
* 2) Integer list of attribute numbers retrieved by the SELECT
*
* These items are indexed with the enum FdwScanPrivateIndex, so an item
* can be fetched with list_nth(). For example, to get the SELECT statement:
* sql = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql));
*/
enum FdwScanPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwScanPrivateSelectSql,
/* Integer list of attribute numbers retrieved by the SELECT */
FdwScanPrivateRetrievedAttrs
};
/*
* Similarly, this enum describes what's kept in the fdw_private list for
* a ModifyTable node referencing a postgres_fdw foreign table. We store:
*
* 1) INSERT/UPDATE/DELETE statement text to be sent to the remote server
* 2) Integer list of target attribute numbers for INSERT/UPDATE
* (NIL for a DELETE)
* 3) Boolean flag showing if the remote query has a RETURNING clause
* 4) Integer list of attribute numbers retrieved by RETURNING, if any
*/
enum FdwModifyPrivateIndex
{
/* SQL statement to execute remotely (as a String node) */
FdwModifyPrivateUpdateSql,
/* Integer list of target attribute numbers for INSERT/UPDATE */
FdwModifyPrivateTargetAttnums,
/* has-returning flag (as an integer Value node) */
FdwModifyPrivateHasReturning,
/* Integer list of attribute numbers retrieved by RETURNING */
FdwModifyPrivateRetrievedAttrs
};
/*
* Execution state of a foreign scan using postgres_fdw.
*/
typedef struct PgFdwScanState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* extracted fdw_private data */
char *query; /* text of SELECT command */
List *retrieved_attrs; /* list of retrieved attribute numbers */
/* for remote query execution */
PGconn *conn; /* connection for the scan */
unsigned int cursor_number; /* quasi-unique ID for my cursor */
bool cursor_exists; /* have we created the cursor? */
int numParams; /* number of parameters passed to query */
FmgrInfo *param_flinfo; /* output conversion functions for them */
List *param_exprs; /* executable expressions for param values */
const char **param_values; /* textual values of query parameters */
/* for storing result tuples */
HeapTuple *tuples; /* array of currently-retrieved tuples */
int num_tuples; /* # of tuples in array */
int next_tuple; /* index of next one to return */
/* batch-level state, for optimizing rewinds and avoiding useless fetch */
int fetch_ct_2; /* Min(# of fetches done, 2) */
bool eof_reached; /* true if last fetch reached EOF */
/* working memory contexts */
MemoryContext batch_cxt; /* context holding current batch of tuples */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwScanState;
/*
* Execution state of a foreign insert/update/delete operation.
*/
typedef struct PgFdwModifyState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
/* for remote query execution */
PGconn *conn; /* connection for the scan */
char *p_name; /* name of prepared statement, if created */
/* extracted fdw_private data */
char *query; /* text of INSERT/UPDATE/DELETE command */
List *target_attrs; /* list of target attribute numbers */
bool has_returning; /* is there a RETURNING clause? */
List *retrieved_attrs; /* attr numbers retrieved by RETURNING */
/* info about parameters for prepared statement */
AttrNumber ctidAttno; /* attnum of input resjunk ctid column */
int p_nums; /* number of parameters to transmit */
FmgrInfo *p_flinfo; /* output conversion functions for them */
/* working memory context */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwModifyState;
/*
* Workspace for analyzing a foreign table.
*/
typedef struct PgFdwAnalyzeState
{
Relation rel; /* relcache entry for the foreign table */
AttInMetadata *attinmeta; /* attribute datatype conversion metadata */
List *retrieved_attrs; /* attr numbers retrieved by query */
/* collected sample rows */
HeapTuple *rows; /* array of size targrows */
int targrows; /* target # of sample rows */
int numrows; /* # of sample rows collected */
/* for random sampling */
double samplerows; /* # of rows fetched */
double rowstoskip; /* # of rows to skip before next sample */
double rstate; /* random state */
/* working memory contexts */
MemoryContext anl_cxt; /* context for per-analyze lifespan data */
MemoryContext temp_cxt; /* context for per-tuple temporary data */
} PgFdwAnalyzeState;
/*
* Identify the attribute where data conversion fails.
*/
typedef struct ConversionLocation
{
Relation rel; /* foreign table's relcache entry */
AttrNumber cur_attno; /* attribute number being processed, or 0 */
} ConversionLocation;
/* Callback argument for ec_member_matches_foreign */
typedef struct
{
Expr *current; /* current expr, or NULL if not yet found */
List *already_used; /* expressions already dealt with */
} ec_member_foreign_arg;
/*
* SQL functions
*/
PG_FUNCTION_INFO_V1(postgres_fdw_handler);
/*
* FDW callback routines
*/
static void postgresGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static void postgresGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid);
static ForeignScan *postgresGetForeignPlan(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses);
static void postgresBeginForeignScan(ForeignScanState *node, int eflags);
static TupleTableSlot *postgresIterateForeignScan(ForeignScanState *node);
static void postgresReScanForeignScan(ForeignScanState *node);
static void postgresEndForeignScan(ForeignScanState *node);
static void postgresAddForeignUpdateTargets(Query *parsetree,
RangeTblEntry *target_rte,
Relation target_relation);
static List *postgresPlanForeignModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index);
static void postgresBeginForeignModify(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo,
List *fdw_private,
int subplan_index,
int eflags);
static TupleTableSlot *postgresExecForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *postgresExecForeignUpdate(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static TupleTableSlot *postgresExecForeignDelete(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot);
static void postgresEndForeignModify(EState *estate,
ResultRelInfo *resultRelInfo);
static int postgresIsForeignRelUpdatable(Relation rel);
static void postgresExplainForeignScan(ForeignScanState *node,
ExplainState *es);
static void postgresExplainForeignModify(ModifyTableState *mtstate,
ResultRelInfo *rinfo,
List *fdw_private,
int subplan_index,
ExplainState *es);
static bool postgresAnalyzeForeignTable(Relation relation,
AcquireSampleRowsFunc *func,
BlockNumber *totalpages);
/*
* Helper functions
*/
static void estimate_path_cost_size(PlannerInfo *root,
RelOptInfo *baserel,
List *join_conds,
double *p_rows, int *p_width,
Cost *p_startup_cost, Cost *p_total_cost);
static void get_remote_estimate(const char *sql,
PGconn *conn,
double *rows,
int *width,
Cost *startup_cost,
Cost *total_cost);
static bool ec_member_matches_foreign(PlannerInfo *root, RelOptInfo *rel,
EquivalenceClass *ec, EquivalenceMember *em,
void *arg);
static void create_cursor(ForeignScanState *node);
static void fetch_more_data(ForeignScanState *node);
static void close_cursor(PGconn *conn, unsigned int cursor_number);
static void prepare_foreign_modify(PgFdwModifyState *fmstate);
static const char **convert_prep_stmt_params(PgFdwModifyState *fmstate,
ItemPointer tupleid,
TupleTableSlot *slot);
static void store_returning_result(PgFdwModifyState *fmstate,
TupleTableSlot *slot, PGresult *res);
static int postgresAcquireSampleRowsFunc(Relation relation, int elevel,
HeapTuple *rows, int targrows,
double *totalrows,
double *totaldeadrows);
static void analyze_row_processor(PGresult *res, int row,
PgFdwAnalyzeState *astate);
static HeapTuple make_tuple_from_result_row(PGresult *res,
int row,
Relation rel,
AttInMetadata *attinmeta,
List *retrieved_attrs,
MemoryContext temp_context);
static void conversion_error_callback(void *arg);
/*
* Foreign-data wrapper handler function: return a struct with pointers
* to my callback routines.
*/
Datum
postgres_fdw_handler(PG_FUNCTION_ARGS)
{
FdwRoutine *routine = makeNode(FdwRoutine);
/* Functions for scanning foreign tables */
routine->GetForeignRelSize = postgresGetForeignRelSize;
routine->GetForeignPaths = postgresGetForeignPaths;
routine->GetForeignPlan = postgresGetForeignPlan;
routine->BeginForeignScan = postgresBeginForeignScan;
routine->IterateForeignScan = postgresIterateForeignScan;
routine->ReScanForeignScan = postgresReScanForeignScan;
routine->EndForeignScan = postgresEndForeignScan;
/* Functions for updating foreign tables */
routine->AddForeignUpdateTargets = postgresAddForeignUpdateTargets;
routine->PlanForeignModify = postgresPlanForeignModify;
routine->BeginForeignModify = postgresBeginForeignModify;
routine->ExecForeignInsert = postgresExecForeignInsert;
routine->ExecForeignUpdate = postgresExecForeignUpdate;
routine->ExecForeignDelete = postgresExecForeignDelete;
routine->EndForeignModify = postgresEndForeignModify;
routine->IsForeignRelUpdatable = postgresIsForeignRelUpdatable;
/* Support functions for EXPLAIN */
routine->ExplainForeignScan = postgresExplainForeignScan;
routine->ExplainForeignModify = postgresExplainForeignModify;
/* Support functions for ANALYZE */
routine->AnalyzeForeignTable = postgresAnalyzeForeignTable;
PG_RETURN_POINTER(routine);
}
/*
* postgresGetForeignRelSize
* Estimate # of rows and width of the result of the scan
*
* We should consider the effect of all baserestrictinfo clauses here, but
* not any join clauses.
*/
static void
postgresGetForeignRelSize(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
PgFdwRelationInfo *fpinfo;
ListCell *lc;
/*
* We use PgFdwRelationInfo to pass various information to subsequent
* functions.
*/
fpinfo = (PgFdwRelationInfo *) palloc0(sizeof(PgFdwRelationInfo));
baserel->fdw_private = (void *) fpinfo;
/* Look up foreign-table catalog info. */
fpinfo->table = GetForeignTable(foreigntableid);
fpinfo->server = GetForeignServer(fpinfo->table->serverid);
/*
* Extract user-settable option values. Note that per-table setting of
* use_remote_estimate overrides per-server setting.
*/
fpinfo->use_remote_estimate = false;
fpinfo->fdw_startup_cost = DEFAULT_FDW_STARTUP_COST;
fpinfo->fdw_tuple_cost = DEFAULT_FDW_TUPLE_COST;
foreach(lc, fpinfo->server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0)
fpinfo->use_remote_estimate = defGetBoolean(def);
else if (strcmp(def->defname, "fdw_startup_cost") == 0)
fpinfo->fdw_startup_cost = strtod(defGetString(def), NULL);
else if (strcmp(def->defname, "fdw_tuple_cost") == 0)
fpinfo->fdw_tuple_cost = strtod(defGetString(def), NULL);
}
foreach(lc, fpinfo->table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "use_remote_estimate") == 0)
{
fpinfo->use_remote_estimate = defGetBoolean(def);
break; /* only need the one value */
}
}
/*
* If the table or the server is configured to use remote estimates,
* identify which user to do remote access as during planning. This
* should match what ExecCheckRTEPerms() does. If we fail due to lack of
* permissions, the query would have failed at runtime anyway.
*/
if (fpinfo->use_remote_estimate)
{
RangeTblEntry *rte = planner_rt_fetch(baserel->relid, root);
Oid userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
fpinfo->user = GetUserMapping(userid, fpinfo->server->serverid);
}
else
fpinfo->user = NULL;
/*
* Identify which baserestrictinfo clauses can be sent to the remote
* server and which can't.
*/
classifyConditions(root, baserel, baserel->baserestrictinfo,
&fpinfo->remote_conds, &fpinfo->local_conds);
/*
* Identify which attributes will need to be retrieved from the remote
* server. These include all attrs needed for joins or final output, plus
* all attrs used in the local_conds. (Note: if we end up using a
* parameterized scan, it's possible that some of the join clauses will be
* sent to the remote and thus we wouldn't really need to retrieve the
* columns used in them. Doesn't seem worth detecting that case though.)
*/
fpinfo->attrs_used = NULL;
pull_varattnos((Node *) baserel->reltargetlist, baserel->relid,
&fpinfo->attrs_used);
foreach(lc, fpinfo->local_conds)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
pull_varattnos((Node *) rinfo->clause, baserel->relid,
&fpinfo->attrs_used);
}
/*
* Compute the selectivity and cost of the local_conds, so we don't have
* to do it over again for each path. The best we can do for these
* conditions is to estimate selectivity on the basis of local statistics.
*/
fpinfo->local_conds_sel = clauselist_selectivity(root,
fpinfo->local_conds,
baserel->relid,
JOIN_INNER,
NULL);
cost_qual_eval(&fpinfo->local_conds_cost, fpinfo->local_conds, root);
/*
* If the table or the server is configured to use remote estimates,
* connect to the foreign server and execute EXPLAIN to estimate the
* number of rows selected by the restriction clauses, as well as the
* average row width. Otherwise, estimate using whatever statistics we
* have locally, in a way similar to ordinary tables.
*/
if (fpinfo->use_remote_estimate)
{
/*
* Get cost/size estimates with help of remote server. Save the
* values in fpinfo so we don't need to do it again to generate the
* basic foreign path.
*/
estimate_path_cost_size(root, baserel, NIL,
&fpinfo->rows, &fpinfo->width,
&fpinfo->startup_cost, &fpinfo->total_cost);
/* Report estimated baserel size to planner. */
baserel->rows = fpinfo->rows;
baserel->width = fpinfo->width;
}
else
{
/*
* If the foreign table has never been ANALYZEd, it will have relpages
* and reltuples equal to zero, which most likely has nothing to do
* with reality. We can't do a whole lot about that if we're not
* allowed to consult the remote server, but we can use a hack similar
* to plancat.c's treatment of empty relations: use a minimum size
* estimate of 10 pages, and divide by the column-datatype-based width
* estimate to get the corresponding number of tuples.
*/
if (baserel->pages == 0 && baserel->tuples == 0)
{
baserel->pages = 10;
baserel->tuples =
(10 * BLCKSZ) / (baserel->width + sizeof(HeapTupleHeaderData));
}
/* Estimate baserel size as best we can with local statistics. */
set_baserel_size_estimates(root, baserel);
/* Fill in basically-bogus cost estimates for use later. */
estimate_path_cost_size(root, baserel, NIL,
&fpinfo->rows, &fpinfo->width,
&fpinfo->startup_cost, &fpinfo->total_cost);
}
}
/*
* postgresGetForeignPaths
* Create possible scan paths for a scan on the foreign table
*/
static void
postgresGetForeignPaths(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) baserel->fdw_private;
ForeignPath *path;
List *ppi_list;
ListCell *lc;
/*
* Create simplest ForeignScan path node and add it to baserel. This path
* corresponds to SeqScan path of regular tables (though depending on what
* baserestrict conditions we were able to send to remote, there might
* actually be an indexscan happening there). We already did all the work
* to estimate cost and size of this path.
*/
path = create_foreignscan_path(root, baserel,
fpinfo->rows,
fpinfo->startup_cost,
fpinfo->total_cost,
NIL, /* no pathkeys */
NULL, /* no outer rel either */
NIL); /* no fdw_private list */
add_path(baserel, (Path *) path);
/*
* If we're not using remote estimates, stop here. We have no way to
* estimate whether any join clauses would be worth sending across, so
* don't bother building parameterized paths.
*/
if (!fpinfo->use_remote_estimate)
return;
/*
* Thumb through all join clauses for the rel to identify which outer
* relations could supply one or more safe-to-send-to-remote join clauses.
* We'll build a parameterized path for each such outer relation.
*
* It's convenient to manage this by representing each candidate outer
* relation by the ParamPathInfo node for it. We can then use the
* ppi_clauses list in the ParamPathInfo node directly as a list of the
* interesting join clauses for that rel. This takes care of the
* possibility that there are multiple safe join clauses for such a rel,
* and also ensures that we account for unsafe join clauses that we'll
* still have to enforce locally (since the parameterized-path machinery
* insists that we handle all movable clauses).
*/
ppi_list = NIL;
foreach(lc, baserel->joininfo)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Relids required_outer;
ParamPathInfo *param_info;
/* Check if clause can be moved to this rel */
if (!join_clause_is_movable_to(rinfo, baserel))
continue;
/* See if it is safe to send to remote */
if (!is_foreign_expr(root, baserel, rinfo->clause))
continue;
/* Calculate required outer rels for the resulting path */
required_outer = bms_union(rinfo->clause_relids,
baserel->lateral_relids);
/* We do not want the foreign rel itself listed in required_outer */
required_outer = bms_del_member(required_outer, baserel->relid);
/*
* required_outer probably can't be empty here, but if it were, we
* couldn't make a parameterized path.
*/
if (bms_is_empty(required_outer))
continue;
/* Get the ParamPathInfo */
param_info = get_baserel_parampathinfo(root, baserel,
required_outer);
Assert(param_info != NULL);
/*
* Add it to list unless we already have it. Testing pointer equality
* is OK since get_baserel_parampathinfo won't make duplicates.
*/
ppi_list = list_append_unique_ptr(ppi_list, param_info);
}
/*
* The above scan examined only "generic" join clauses, not those that
* were absorbed into EquivalenceClauses. See if we can make anything out
* of EquivalenceClauses.
*/
if (baserel->has_eclass_joins)
{
/*
* We repeatedly scan the eclass list looking for column references
* (or expressions) belonging to the foreign rel. Each time we find
* one, we generate a list of equivalence joinclauses for it, and then
* see if any are safe to send to the remote. Repeat till there are
* no more candidate EC members.
*/
ec_member_foreign_arg arg;
arg.already_used = NIL;
for (;;)
{
List *clauses;
/* Make clauses, skipping any that join to lateral_referencers */
arg.current = NULL;
clauses = generate_implied_equalities_for_column(root,
baserel,
ec_member_matches_foreign,
(void *) &arg,
baserel->lateral_referencers);
/* Done if there are no more expressions in the foreign rel */
if (arg.current == NULL)
{
Assert(clauses == NIL);
break;
}
/* Scan the extracted join clauses */
foreach(lc, clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Relids required_outer;
ParamPathInfo *param_info;
/* Check if clause can be moved to this rel */
if (!join_clause_is_movable_to(rinfo, baserel))
continue;
/* See if it is safe to send to remote */
if (!is_foreign_expr(root, baserel, rinfo->clause))
continue;
/* Calculate required outer rels for the resulting path */
required_outer = bms_union(rinfo->clause_relids,
baserel->lateral_relids);
required_outer = bms_del_member(required_outer, baserel->relid);
if (bms_is_empty(required_outer))
continue;
/* Get the ParamPathInfo */
param_info = get_baserel_parampathinfo(root, baserel,
required_outer);
Assert(param_info != NULL);
/* Add it to list unless we already have it */
ppi_list = list_append_unique_ptr(ppi_list, param_info);
}
/* Try again, now ignoring the expression we found this time */
arg.already_used = lappend(arg.already_used, arg.current);
}
}
/*
* Now build a path for each useful outer relation.
*/
foreach(lc, ppi_list)
{
ParamPathInfo *param_info = (ParamPathInfo *) lfirst(lc);
double rows;
int width;
Cost startup_cost;
Cost total_cost;
/* Get a cost estimate from the remote */
estimate_path_cost_size(root, baserel,
param_info->ppi_clauses,
&rows, &width,
&startup_cost, &total_cost);
/*
* ppi_rows currently won't get looked at by anything, but still we
* may as well ensure that it matches our idea of the rowcount.
*/
param_info->ppi_rows = rows;
/* Make the path */
path = create_foreignscan_path(root, baserel,
rows,
startup_cost,
total_cost,
NIL, /* no pathkeys */
param_info->ppi_req_outer,
NIL); /* no fdw_private list */
add_path(baserel, (Path *) path);
}
}
/*
* postgresGetForeignPlan
* Create ForeignScan plan node which implements selected best path
*/
static ForeignScan *
postgresGetForeignPlan(PlannerInfo *root,
RelOptInfo *baserel,
Oid foreigntableid,
ForeignPath *best_path,
List *tlist,
List *scan_clauses)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) baserel->fdw_private;
Index scan_relid = baserel->relid;
List *fdw_private;
List *remote_conds = NIL;
List *local_exprs = NIL;
List *params_list = NIL;
List *retrieved_attrs;
StringInfoData sql;
ListCell *lc;
/*
* Separate the scan_clauses into those that can be executed remotely and
* those that can't. baserestrictinfo clauses that were previously
* determined to be safe or unsafe by classifyConditions are shown in
* fpinfo->remote_conds and fpinfo->local_conds. Anything else in the
* scan_clauses list will be a join clause, which we have to check for
* remote-safety.
*
* Note: the join clauses we see here should be the exact same ones
* previously examined by postgresGetForeignPaths. Possibly it'd be worth
* passing forward the classification work done then, rather than
* repeating it here.
*
* This code must match "extract_actual_clauses(scan_clauses, false)"
* except for the additional decision about remote versus local execution.
* Note however that we only strip the RestrictInfo nodes from the
* local_exprs list, since appendWhereClause expects a list of
* RestrictInfos.
*/
foreach(lc, scan_clauses)
{
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Assert(IsA(rinfo, RestrictInfo));
/* Ignore any pseudoconstants, they're dealt with elsewhere */
if (rinfo->pseudoconstant)
continue;
if (list_member_ptr(fpinfo->remote_conds, rinfo))
remote_conds = lappend(remote_conds, rinfo);
else if (list_member_ptr(fpinfo->local_conds, rinfo))
local_exprs = lappend(local_exprs, rinfo->clause);
else if (is_foreign_expr(root, baserel, rinfo->clause))
remote_conds = lappend(remote_conds, rinfo);
else
local_exprs = lappend(local_exprs, rinfo->clause);
}
/*
* Build the query string to be sent for execution, and identify
* expressions to be sent as parameters.
*/
initStringInfo(&sql);
deparseSelectSql(&sql, root, baserel, fpinfo->attrs_used,
&retrieved_attrs);
if (remote_conds)
appendWhereClause(&sql, root, baserel, remote_conds,
true, ¶ms_list);
/*
* Add FOR UPDATE/SHARE if appropriate. We apply locking during the
* initial row fetch, rather than later on as is done for local tables.
* The extra roundtrips involved in trying to duplicate the local
* semantics exactly don't seem worthwhile (see also comments for
* RowMarkType).
*
* Note: because we actually run the query as a cursor, this assumes that
* DECLARE CURSOR ... FOR UPDATE is supported, which it isn't before 8.3.
*/
if (baserel->relid == root->parse->resultRelation &&
(root->parse->commandType == CMD_UPDATE ||
root->parse->commandType == CMD_DELETE))
{
/* Relation is UPDATE/DELETE target, so use FOR UPDATE */
appendStringInfoString(&sql, " FOR UPDATE");
}
else
{
RowMarkClause *rc = get_parse_rowmark(root->parse, baserel->relid);
if (rc)
{
/*
* Relation is specified as a FOR UPDATE/SHARE target, so handle
* that.
*
* For now, just ignore any [NO] KEY specification, since (a) it's
* not clear what that means for a remote table that we don't have
* complete information about, and (b) it wouldn't work anyway on
* older remote servers. Likewise, we don't worry about NOWAIT.
*/
switch (rc->strength)
{
case LCS_FORKEYSHARE:
case LCS_FORSHARE:
appendStringInfoString(&sql, " FOR SHARE");
break;
case LCS_FORNOKEYUPDATE:
case LCS_FORUPDATE:
appendStringInfoString(&sql, " FOR UPDATE");
break;
}
}
}
/*
* Build the fdw_private list that will be available to the executor.
* Items in the list must match enum FdwScanPrivateIndex, above.
*/
fdw_private = list_make2(makeString(sql.data),
retrieved_attrs);
/*
* Create the ForeignScan node from target list, local filtering
* expressions, remote parameter expressions, and FDW private information.
*
* Note that the remote parameter expressions are stored in the fdw_exprs
* field of the finished plan node; we can't keep them in private state
* because then they wouldn't be subject to later planner processing.
*/
return make_foreignscan(tlist,
local_exprs,
scan_relid,
params_list,
fdw_private);
}
/*
* postgresBeginForeignScan
* Initiate an executor scan of a foreign PostgreSQL table.
*/
static void
postgresBeginForeignScan(ForeignScanState *node, int eflags)
{
ForeignScan *fsplan = (ForeignScan *) node->ss.ps.plan;
EState *estate = node->ss.ps.state;
PgFdwScanState *fsstate;
RangeTblEntry *rte;
Oid userid;
ForeignTable *table;
ForeignServer *server;
UserMapping *user;
int numParams;
int i;
ListCell *lc;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. node->fdw_state stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/*
* We'll save private state in node->fdw_state.
*/
fsstate = (PgFdwScanState *) palloc0(sizeof(PgFdwScanState));
node->fdw_state = (void *) fsstate;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does.
*/
rte = rt_fetch(fsplan->scan.scanrelid, estate->es_range_table);
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
fsstate->rel = node->ss.ss_currentRelation;
table = GetForeignTable(RelationGetRelid(fsstate->rel));
server = GetForeignServer(table->serverid);
user = GetUserMapping(userid, server->serverid);
/*
* Get connection to the foreign server. Connection manager will
* establish new connection if necessary.
*/
fsstate->conn = GetConnection(server, user, false);
/* Assign a unique ID for my cursor */
fsstate->cursor_number = GetCursorNumber(fsstate->conn);
fsstate->cursor_exists = false;
/* Get private info created by planner functions. */
fsstate->query = strVal(list_nth(fsplan->fdw_private,
FdwScanPrivateSelectSql));
fsstate->retrieved_attrs = (List *) list_nth(fsplan->fdw_private,
FdwScanPrivateRetrievedAttrs);
/* Create contexts for batches of tuples and per-tuple temp workspace. */
fsstate->batch_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw tuple data",
ALLOCSET_DEFAULT_MINSIZE,
ALLOCSET_DEFAULT_INITSIZE,
ALLOCSET_DEFAULT_MAXSIZE);
fsstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw temporary data",
ALLOCSET_SMALL_MINSIZE,
ALLOCSET_SMALL_INITSIZE,
ALLOCSET_SMALL_MAXSIZE);
/* Get info we'll need for input data conversion. */
fsstate->attinmeta = TupleDescGetAttInMetadata(RelationGetDescr(fsstate->rel));
/* Prepare for output conversion of parameters used in remote query. */
numParams = list_length(fsplan->fdw_exprs);
fsstate->numParams = numParams;
fsstate->param_flinfo = (FmgrInfo *) palloc0(sizeof(FmgrInfo) * numParams);
i = 0;
foreach(lc, fsplan->fdw_exprs)
{
Node *param_expr = (Node *) lfirst(lc);
Oid typefnoid;
bool isvarlena;
getTypeOutputInfo(exprType(param_expr), &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fsstate->param_flinfo[i]);
i++;
}
/*
* Prepare remote-parameter expressions for evaluation. (Note: in
* practice, we expect that all these expressions will be just Params, so
* we could possibly do something more efficient than using the full
* expression-eval machinery for this. But probably there would be little
* benefit, and it'd require postgres_fdw to know more than is desirable
* about Param evaluation.)
*/
fsstate->param_exprs = (List *)
ExecInitExpr((Expr *) fsplan->fdw_exprs,
(PlanState *) node);
/*
* Allocate buffer for text form of query parameters, if any.
*/
if (numParams > 0)
fsstate->param_values = (const char **) palloc0(numParams * sizeof(char *));
else
fsstate->param_values = NULL;
}
/*
* postgresIterateForeignScan
* Retrieve next row from the result set, or clear tuple slot to indicate
* EOF.
*/
static TupleTableSlot *
postgresIterateForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
TupleTableSlot *slot = node->ss.ss_ScanTupleSlot;
/*
* If this is the first call after Begin or ReScan, we need to create the
* cursor on the remote side.
*/
if (!fsstate->cursor_exists)
create_cursor(node);
/*
* Get some more tuples, if we've run out.
*/
if (fsstate->next_tuple >= fsstate->num_tuples)
{
/* No point in another fetch if we already detected EOF, though. */
if (!fsstate->eof_reached)
fetch_more_data(node);
/* If we didn't get any tuples, must be end of data. */
if (fsstate->next_tuple >= fsstate->num_tuples)
return ExecClearTuple(slot);
}
/*
* Return the next tuple.
*/
ExecStoreTuple(fsstate->tuples[fsstate->next_tuple++],
slot,
InvalidBuffer,
false);
return slot;
}
/*
* postgresReScanForeignScan
* Restart the scan.
*/
static void
postgresReScanForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
char sql[64];
PGresult *res;
/* If we haven't created the cursor yet, nothing to do. */
if (!fsstate->cursor_exists)
return;
/*
* If any internal parameters affecting this node have changed, we'd
* better destroy and recreate the cursor. Otherwise, rewinding it should
* be good enough. If we've only fetched zero or one batch, we needn't
* even rewind the cursor, just rescan what we have.
*/
if (node->ss.ps.chgParam != NULL)
{
fsstate->cursor_exists = false;
snprintf(sql, sizeof(sql), "CLOSE c%u",
fsstate->cursor_number);
}
else if (fsstate->fetch_ct_2 > 1)
{
snprintf(sql, sizeof(sql), "MOVE BACKWARD ALL IN c%u",
fsstate->cursor_number);
}
else
{
/* Easy: just rescan what we already have in memory, if anything */
fsstate->next_tuple = 0;
return;
}
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexec(fsstate->conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, fsstate->conn, true, sql);
PQclear(res);
/* Now force a fresh FETCH. */
fsstate->tuples = NULL;
fsstate->num_tuples = 0;
fsstate->next_tuple = 0;
fsstate->fetch_ct_2 = 0;
fsstate->eof_reached = false;
}
/*
* postgresEndForeignScan
* Finish scanning foreign table and dispose objects used for this scan
*/
static void
postgresEndForeignScan(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
/* if fsstate is NULL, we are in EXPLAIN; nothing to do */
if (fsstate == NULL)
return;
/* Close the cursor if open, to prevent accumulation of cursors */
if (fsstate->cursor_exists)
close_cursor(fsstate->conn, fsstate->cursor_number);
/* Release remote connection */
ReleaseConnection(fsstate->conn);
fsstate->conn = NULL;
/* MemoryContexts will be deleted automatically. */
}
/*
* postgresAddForeignUpdateTargets
* Add resjunk column(s) needed for update/delete on a foreign table
*/
static void
postgresAddForeignUpdateTargets(Query *parsetree,
RangeTblEntry *target_rte,
Relation target_relation)
{
Var *var;
const char *attrname;
TargetEntry *tle;
/*
* In postgres_fdw, what we need is the ctid, same as for a regular table.
*/
/* Make a Var representing the desired value */
var = makeVar(parsetree->resultRelation,
SelfItemPointerAttributeNumber,
TIDOID,
-1,
InvalidOid,
0);
/* Wrap it in a resjunk TLE with the right name ... */
attrname = "ctid";
tle = makeTargetEntry((Expr *) var,
list_length(parsetree->targetList) + 1,
pstrdup(attrname),
true);
/* ... and add it to the query's targetlist */
parsetree->targetList = lappend(parsetree->targetList, tle);
}
/*
* postgresPlanForeignModify
* Plan an insert/update/delete operation on a foreign table
*
* Note: currently, the plan tree generated for UPDATE/DELETE will always
* include a ForeignScan that retrieves ctids (using SELECT FOR UPDATE)
* and then the ModifyTable node will have to execute individual remote
* UPDATE/DELETE commands. If there are no local conditions or joins
* needed, it'd be better to let the scan node do UPDATE/DELETE RETURNING
* and then do nothing at ModifyTable. Room for future optimization ...
*/
static List *
postgresPlanForeignModify(PlannerInfo *root,
ModifyTable *plan,
Index resultRelation,
int subplan_index)
{
CmdType operation = plan->operation;
RangeTblEntry *rte = planner_rt_fetch(resultRelation, root);
Relation rel;
StringInfoData sql;
List *targetAttrs = NIL;
List *returningList = NIL;
List *retrieved_attrs = NIL;
initStringInfo(&sql);
/*
* Core code already has some lock on each rel being planned, so we can
* use NoLock here.
*/
rel = heap_open(rte->relid, NoLock);
/*
* In an INSERT, we transmit all columns that are defined in the foreign
* table. In an UPDATE, we transmit only columns that were explicitly
* targets of the UPDATE, so as to avoid unnecessary data transmission.
* (We can't do that for INSERT since we would miss sending default values
* for columns not listed in the source statement.)
*/
if (operation == CMD_INSERT)
{
TupleDesc tupdesc = RelationGetDescr(rel);
int attnum;
for (attnum = 1; attnum <= tupdesc->natts; attnum++)
{
Form_pg_attribute attr = tupdesc->attrs[attnum - 1];
if (!attr->attisdropped)
targetAttrs = lappend_int(targetAttrs, attnum);
}
}
else if (operation == CMD_UPDATE)
{
Bitmapset *tmpset = bms_copy(rte->modifiedCols);
AttrNumber col;
while ((col = bms_first_member(tmpset)) >= 0)
{
col += FirstLowInvalidHeapAttributeNumber;
if (col <= InvalidAttrNumber) /* shouldn't happen */
elog(ERROR, "system-column update is not supported");
targetAttrs = lappend_int(targetAttrs, col);
}
}
/*
* Extract the relevant RETURNING list if any.
*/
if (plan->returningLists)
returningList = (List *) list_nth(plan->returningLists, subplan_index);
/*
* Construct the SQL command string.
*/
switch (operation)
{
case CMD_INSERT:
deparseInsertSql(&sql, root, resultRelation, rel,
targetAttrs, returningList,
&retrieved_attrs);
break;
case CMD_UPDATE:
deparseUpdateSql(&sql, root, resultRelation, rel,
targetAttrs, returningList,
&retrieved_attrs);
break;
case CMD_DELETE:
deparseDeleteSql(&sql, root, resultRelation, rel,
returningList,
&retrieved_attrs);
break;
default:
elog(ERROR, "unexpected operation: %d", (int) operation);
break;
}
heap_close(rel, NoLock);
/*
* Build the fdw_private list that will be available to the executor.
* Items in the list must match enum FdwModifyPrivateIndex, above.
*/
return list_make4(makeString(sql.data),
targetAttrs,
makeInteger((retrieved_attrs != NIL)),
retrieved_attrs);
}
/*
* postgresBeginForeignModify
* Begin an insert/update/delete operation on a foreign table
*/
static void
postgresBeginForeignModify(ModifyTableState *mtstate,
ResultRelInfo *resultRelInfo,
List *fdw_private,
int subplan_index,
int eflags)
{
PgFdwModifyState *fmstate;
EState *estate = mtstate->ps.state;
CmdType operation = mtstate->operation;
Relation rel = resultRelInfo->ri_RelationDesc;
RangeTblEntry *rte;
Oid userid;
ForeignTable *table;
ForeignServer *server;
UserMapping *user;
AttrNumber n_params;
Oid typefnoid;
bool isvarlena;
ListCell *lc;
/*
* Do nothing in EXPLAIN (no ANALYZE) case. resultRelInfo->ri_FdwState
* stays NULL.
*/
if (eflags & EXEC_FLAG_EXPLAIN_ONLY)
return;
/* Begin constructing PgFdwModifyState. */
fmstate = (PgFdwModifyState *) palloc0(sizeof(PgFdwModifyState));
fmstate->rel = rel;
/*
* Identify which user to do the remote access as. This should match what
* ExecCheckRTEPerms() does.
*/
rte = rt_fetch(resultRelInfo->ri_RangeTableIndex, estate->es_range_table);
userid = rte->checkAsUser ? rte->checkAsUser : GetUserId();
/* Get info about foreign table. */
table = GetForeignTable(RelationGetRelid(rel));
server = GetForeignServer(table->serverid);
user = GetUserMapping(userid, server->serverid);
/* Open connection; report that we'll create a prepared statement. */
fmstate->conn = GetConnection(server, user, true);
fmstate->p_name = NULL; /* prepared statement not made yet */
/* Deconstruct fdw_private data. */
fmstate->query = strVal(list_nth(fdw_private,
FdwModifyPrivateUpdateSql));
fmstate->target_attrs = (List *) list_nth(fdw_private,
FdwModifyPrivateTargetAttnums);
fmstate->has_returning = intVal(list_nth(fdw_private,
FdwModifyPrivateHasReturning));
fmstate->retrieved_attrs = (List *) list_nth(fdw_private,
FdwModifyPrivateRetrievedAttrs);
/* Create context for per-tuple temp workspace. */
fmstate->temp_cxt = AllocSetContextCreate(estate->es_query_cxt,
"postgres_fdw temporary data",
ALLOCSET_SMALL_MINSIZE,
ALLOCSET_SMALL_INITSIZE,
ALLOCSET_SMALL_MAXSIZE);
/* Prepare for input conversion of RETURNING results. */
if (fmstate->has_returning)
fmstate->attinmeta = TupleDescGetAttInMetadata(RelationGetDescr(rel));
/* Prepare for output conversion of parameters used in prepared stmt. */
n_params = list_length(fmstate->target_attrs) + 1;
fmstate->p_flinfo = (FmgrInfo *) palloc0(sizeof(FmgrInfo) * n_params);
fmstate->p_nums = 0;
if (operation == CMD_UPDATE || operation == CMD_DELETE)
{
/* Find the ctid resjunk column in the subplan's result */
Plan *subplan = mtstate->mt_plans[subplan_index]->plan;
fmstate->ctidAttno = ExecFindJunkAttributeInTlist(subplan->targetlist,
"ctid");
if (!AttributeNumberIsValid(fmstate->ctidAttno))
elog(ERROR, "could not find junk ctid column");
/* First transmittable parameter will be ctid */
getTypeOutputInfo(TIDOID, &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
fmstate->p_nums++;
}
if (operation == CMD_INSERT || operation == CMD_UPDATE)
{
/* Set up for remaining transmittable parameters */
foreach(lc, fmstate->target_attrs)
{
int attnum = lfirst_int(lc);
Form_pg_attribute attr = RelationGetDescr(rel)->attrs[attnum - 1];
Assert(!attr->attisdropped);
getTypeOutputInfo(attr->atttypid, &typefnoid, &isvarlena);
fmgr_info(typefnoid, &fmstate->p_flinfo[fmstate->p_nums]);
fmstate->p_nums++;
}
}
Assert(fmstate->p_nums <= n_params);
resultRelInfo->ri_FdwState = fmstate;
}
/*
* postgresExecForeignInsert
* Insert one row into a foreign table
*/
static TupleTableSlot *
postgresExecForeignInsert(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
const char **p_values;
PGresult *res;
int n_rows;
/* Set up the prepared statement on the remote server, if we didn't yet */
if (!fmstate->p_name)
prepare_foreign_modify(fmstate);
/* Convert parameters needed by prepared statement to text form */
p_values = convert_prep_stmt_params(fmstate, NULL, slot);
/*
* Execute the prepared statement, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexecPrepared(fmstate->conn,
fmstate->p_name,
fmstate->p_nums,
p_values,
NULL,
NULL,
0);
if (PQresultStatus(res) !=
(fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
/* Check number of rows affected, and fetch RETURNING tuple if any */
if (fmstate->has_returning)
{
n_rows = PQntuples(res);
if (n_rows > 0)
store_returning_result(fmstate, slot, res);
}
else
n_rows = atoi(PQcmdTuples(res));
/* And clean up */
PQclear(res);
MemoryContextReset(fmstate->temp_cxt);
/* Return NULL if nothing was inserted on the remote end */
return (n_rows > 0) ? slot : NULL;
}
/*
* postgresExecForeignUpdate
* Update one row in a foreign table
*/
static TupleTableSlot *
postgresExecForeignUpdate(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
Datum datum;
bool isNull;
const char **p_values;
PGresult *res;
int n_rows;
/* Set up the prepared statement on the remote server, if we didn't yet */
if (!fmstate->p_name)
prepare_foreign_modify(fmstate);
/* Get the ctid that was passed up as a resjunk column */
datum = ExecGetJunkAttribute(planSlot,
fmstate->ctidAttno,
&isNull);
/* shouldn't ever get a null result... */
if (isNull)
elog(ERROR, "ctid is NULL");
/* Convert parameters needed by prepared statement to text form */
p_values = convert_prep_stmt_params(fmstate,
(ItemPointer) DatumGetPointer(datum),
slot);
/*
* Execute the prepared statement, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexecPrepared(fmstate->conn,
fmstate->p_name,
fmstate->p_nums,
p_values,
NULL,
NULL,
0);
if (PQresultStatus(res) !=
(fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
/* Check number of rows affected, and fetch RETURNING tuple if any */
if (fmstate->has_returning)
{
n_rows = PQntuples(res);
if (n_rows > 0)
store_returning_result(fmstate, slot, res);
}
else
n_rows = atoi(PQcmdTuples(res));
/* And clean up */
PQclear(res);
MemoryContextReset(fmstate->temp_cxt);
/* Return NULL if nothing was updated on the remote end */
return (n_rows > 0) ? slot : NULL;
}
/*
* postgresExecForeignDelete
* Delete one row from a foreign table
*/
static TupleTableSlot *
postgresExecForeignDelete(EState *estate,
ResultRelInfo *resultRelInfo,
TupleTableSlot *slot,
TupleTableSlot *planSlot)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
Datum datum;
bool isNull;
const char **p_values;
PGresult *res;
int n_rows;
/* Set up the prepared statement on the remote server, if we didn't yet */
if (!fmstate->p_name)
prepare_foreign_modify(fmstate);
/* Get the ctid that was passed up as a resjunk column */
datum = ExecGetJunkAttribute(planSlot,
fmstate->ctidAttno,
&isNull);
/* shouldn't ever get a null result... */
if (isNull)
elog(ERROR, "ctid is NULL");
/* Convert parameters needed by prepared statement to text form */
p_values = convert_prep_stmt_params(fmstate,
(ItemPointer) DatumGetPointer(datum),
NULL);
/*
* Execute the prepared statement, and check for success.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexecPrepared(fmstate->conn,
fmstate->p_name,
fmstate->p_nums,
p_values,
NULL,
NULL,
0);
if (PQresultStatus(res) !=
(fmstate->has_returning ? PGRES_TUPLES_OK : PGRES_COMMAND_OK))
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
/* Check number of rows affected, and fetch RETURNING tuple if any */
if (fmstate->has_returning)
{
n_rows = PQntuples(res);
if (n_rows > 0)
store_returning_result(fmstate, slot, res);
}
else
n_rows = atoi(PQcmdTuples(res));
/* And clean up */
PQclear(res);
MemoryContextReset(fmstate->temp_cxt);
/* Return NULL if nothing was deleted on the remote end */
return (n_rows > 0) ? slot : NULL;
}
/*
* postgresEndForeignModify
* Finish an insert/update/delete operation on a foreign table
*/
static void
postgresEndForeignModify(EState *estate,
ResultRelInfo *resultRelInfo)
{
PgFdwModifyState *fmstate = (PgFdwModifyState *) resultRelInfo->ri_FdwState;
/* If fmstate is NULL, we are in EXPLAIN; nothing to do */
if (fmstate == NULL)
return;
/* If we created a prepared statement, destroy it */
if (fmstate->p_name)
{
char sql[64];
PGresult *res;
snprintf(sql, sizeof(sql), "DEALLOCATE %s", fmstate->p_name);
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexec(fmstate->conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, fmstate->conn, true, sql);
PQclear(res);
fmstate->p_name = NULL;
}
/* Release remote connection */
ReleaseConnection(fmstate->conn);
fmstate->conn = NULL;
}
/*
* postgresIsForeignRelUpdatable
* Determine whether a foreign table supports INSERT, UPDATE and/or
* DELETE.
*/
static int
postgresIsForeignRelUpdatable(Relation rel)
{
bool updatable;
ForeignTable *table;
ForeignServer *server;
ListCell *lc;
/*
* By default, all postgres_fdw foreign tables are assumed updatable. This
* can be overridden by a per-server setting, which in turn can be
* overridden by a per-table setting.
*/
updatable = true;
table = GetForeignTable(RelationGetRelid(rel));
server = GetForeignServer(table->serverid);
foreach(lc, server->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "updatable") == 0)
updatable = defGetBoolean(def);
}
foreach(lc, table->options)
{
DefElem *def = (DefElem *) lfirst(lc);
if (strcmp(def->defname, "updatable") == 0)
updatable = defGetBoolean(def);
}
/*
* Currently "updatable" means support for INSERT, UPDATE and DELETE.
*/
return updatable ?
(1 << CMD_INSERT) | (1 << CMD_UPDATE) | (1 << CMD_DELETE) : 0;
}
/*
* postgresExplainForeignScan
* Produce extra output for EXPLAIN of a ForeignScan on a foreign table
*/
static void
postgresExplainForeignScan(ForeignScanState *node, ExplainState *es)
{
List *fdw_private;
char *sql;
if (es->verbose)
{
fdw_private = ((ForeignScan *) node->ss.ps.plan)->fdw_private;
sql = strVal(list_nth(fdw_private, FdwScanPrivateSelectSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
/*
* postgresExplainForeignModify
* Produce extra output for EXPLAIN of a ModifyTable on a foreign table
*/
static void
postgresExplainForeignModify(ModifyTableState *mtstate,
ResultRelInfo *rinfo,
List *fdw_private,
int subplan_index,
ExplainState *es)
{
if (es->verbose)
{
char *sql = strVal(list_nth(fdw_private,
FdwModifyPrivateUpdateSql));
ExplainPropertyText("Remote SQL", sql, es);
}
}
/*
* estimate_path_cost_size
* Get cost and size estimates for a foreign scan
*
* We assume that all the baserestrictinfo clauses will be applied, plus
* any join clauses listed in join_conds.
*/
static void
estimate_path_cost_size(PlannerInfo *root,
RelOptInfo *baserel,
List *join_conds,
double *p_rows, int *p_width,
Cost *p_startup_cost, Cost *p_total_cost)
{
PgFdwRelationInfo *fpinfo = (PgFdwRelationInfo *) baserel->fdw_private;
double rows;
double retrieved_rows;
int width;
Cost startup_cost;
Cost total_cost;
Cost run_cost;
Cost cpu_per_tuple;
/*
* If the table or the server is configured to use remote estimates,
* connect to the foreign server and execute EXPLAIN to estimate the
* number of rows selected by the restriction+join clauses. Otherwise,
* estimate rows using whatever statistics we have locally, in a way
* similar to ordinary tables.
*/
if (fpinfo->use_remote_estimate)
{
List *remote_join_conds;
List *local_join_conds;
StringInfoData sql;
List *retrieved_attrs;
PGconn *conn;
Selectivity local_sel;
QualCost local_cost;
/*
* join_conds might contain both clauses that are safe to send across,
* and clauses that aren't.
*/
classifyConditions(root, baserel, join_conds,
&remote_join_conds, &local_join_conds);
/*
* Construct EXPLAIN query including the desired SELECT, FROM, and
* WHERE clauses. Params and other-relation Vars are replaced by
* dummy values.
*/
initStringInfo(&sql);
appendStringInfoString(&sql, "EXPLAIN ");
deparseSelectSql(&sql, root, baserel, fpinfo->attrs_used,
&retrieved_attrs);
if (fpinfo->remote_conds)
appendWhereClause(&sql, root, baserel, fpinfo->remote_conds,
true, NULL);
if (remote_join_conds)
appendWhereClause(&sql, root, baserel, remote_join_conds,
(fpinfo->remote_conds == NIL), NULL);
/* Get the remote estimate */
conn = GetConnection(fpinfo->server, fpinfo->user, false);
get_remote_estimate(sql.data, conn, &rows, &width,
&startup_cost, &total_cost);
ReleaseConnection(conn);
retrieved_rows = rows;
/* Factor in the selectivity of the locally-checked quals */
local_sel = clauselist_selectivity(root,
local_join_conds,
baserel->relid,
JOIN_INNER,
NULL);
local_sel *= fpinfo->local_conds_sel;
rows = clamp_row_est(rows * local_sel);
/* Add in the eval cost of the locally-checked quals */
startup_cost += fpinfo->local_conds_cost.startup;
total_cost += fpinfo->local_conds_cost.per_tuple * retrieved_rows;
cost_qual_eval(&local_cost, local_join_conds, root);
startup_cost += local_cost.startup;
total_cost += local_cost.per_tuple * retrieved_rows;
}
else
{
/*
* We don't support join conditions in this mode (hence, no
* parameterized paths can be made).
*/
Assert(join_conds == NIL);
/* Use rows/width estimates made by set_baserel_size_estimates. */
rows = baserel->rows;
width = baserel->width;
/*
* Back into an estimate of the number of retrieved rows. Just in
* case this is nuts, clamp to at most baserel->tuples.
*/
retrieved_rows = clamp_row_est(rows / fpinfo->local_conds_sel);
retrieved_rows = Min(retrieved_rows, baserel->tuples);
/*
* Cost as though this were a seqscan, which is pessimistic. We
* effectively imagine the local_conds are being evaluated remotely,
* too.
*/
startup_cost = 0;
run_cost = 0;
run_cost += seq_page_cost * baserel->pages;
startup_cost += baserel->baserestrictcost.startup;
cpu_per_tuple = cpu_tuple_cost + baserel->baserestrictcost.per_tuple;
run_cost += cpu_per_tuple * baserel->tuples;
total_cost = startup_cost + run_cost;
}
/*
* Add some additional cost factors to account for connection overhead
* (fdw_startup_cost), transferring data across the network
* (fdw_tuple_cost per retrieved row), and local manipulation of the data
* (cpu_tuple_cost per retrieved row).
*/
startup_cost += fpinfo->fdw_startup_cost;
total_cost += fpinfo->fdw_startup_cost;
total_cost += fpinfo->fdw_tuple_cost * retrieved_rows;
total_cost += cpu_tuple_cost * retrieved_rows;
/* Return results. */
*p_rows = rows;
*p_width = width;
*p_startup_cost = startup_cost;
*p_total_cost = total_cost;
}
/*
* Estimate costs of executing a SQL statement remotely.
* The given "sql" must be an EXPLAIN command.
*/
static void
get_remote_estimate(const char *sql, PGconn *conn,
double *rows, int *width,
Cost *startup_cost, Cost *total_cost)
{
PGresult *volatile res = NULL;
/* PGresult must be released before leaving this function. */
PG_TRY();
{
char *line;
char *p;
int n;
/*
* Execute EXPLAIN remotely.
*/
res = PQexec(conn, sql);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, sql);
/*
* Extract cost numbers for topmost plan node. Note we search for a
* left paren from the end of the line to avoid being confused by
* other uses of parentheses.
*/
line = PQgetvalue(res, 0, 0);
p = strrchr(line, '(');
if (p == NULL)
elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line);
n = sscanf(p, "(cost=%lf..%lf rows=%lf width=%d)",
startup_cost, total_cost, rows, width);
if (n != 4)
elog(ERROR, "could not interpret EXPLAIN output: \"%s\"", line);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* Detect whether we want to process an EquivalenceClass member.
*
* This is a callback for use by generate_implied_equalities_for_column.
*/
static bool
ec_member_matches_foreign(PlannerInfo *root, RelOptInfo *rel,
EquivalenceClass *ec, EquivalenceMember *em,
void *arg)
{
ec_member_foreign_arg *state = (ec_member_foreign_arg *) arg;
Expr *expr = em->em_expr;
/*
* If we've identified what we're processing in the current scan, we only
* want to match that expression.
*/
if (state->current != NULL)
return equal(expr, state->current);
/*
* Otherwise, ignore anything we've already processed.
*/
if (list_member(state->already_used, expr))
return false;
/* This is the new target to process. */
state->current = expr;
return true;
}
/*
* Create cursor for node's query with current parameter values.
*/
static void
create_cursor(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
ExprContext *econtext = node->ss.ps.ps_ExprContext;
int numParams = fsstate->numParams;
const char **values = fsstate->param_values;
PGconn *conn = fsstate->conn;
StringInfoData buf;
PGresult *res;
/*
* Construct array of query parameter values in text format. We do the
* conversions in the short-lived per-tuple context, so as not to cause a
* memory leak over repeated scans.
*/
if (numParams > 0)
{
int nestlevel;
MemoryContext oldcontext;
int i;
ListCell *lc;
oldcontext = MemoryContextSwitchTo(econtext->ecxt_per_tuple_memory);
nestlevel = set_transmission_modes();
i = 0;
foreach(lc, fsstate->param_exprs)
{
ExprState *expr_state = (ExprState *) lfirst(lc);
Datum expr_value;
bool isNull;
/* Evaluate the parameter expression */
expr_value = ExecEvalExpr(expr_state, econtext, &isNull, NULL);
/*
* Get string representation of each parameter value by invoking
* type-specific output function, unless the value is null.
*/
if (isNull)
values[i] = NULL;
else
values[i] = OutputFunctionCall(&fsstate->param_flinfo[i],
expr_value);
i++;
}
reset_transmission_modes(nestlevel);
MemoryContextSwitchTo(oldcontext);
}
/* Construct the DECLARE CURSOR command */
initStringInfo(&buf);
appendStringInfo(&buf, "DECLARE c%u CURSOR FOR\n%s",
fsstate->cursor_number, fsstate->query);
/*
* Notice that we pass NULL for paramTypes, thus forcing the remote server
* to infer types for all parameters. Since we explicitly cast every
* parameter (see deparse.c), the "inference" is trivial and will produce
* the desired result. This allows us to avoid assuming that the remote
* server has the same OIDs we do for the parameters' types.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexecParams(conn, buf.data, numParams, NULL, values,
NULL, NULL, 0);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, conn, true, fsstate->query);
PQclear(res);
/* Mark the cursor as created, and show no tuples have been retrieved */
fsstate->cursor_exists = true;
fsstate->tuples = NULL;
fsstate->num_tuples = 0;
fsstate->next_tuple = 0;
fsstate->fetch_ct_2 = 0;
fsstate->eof_reached = false;
/* Clean up */
pfree(buf.data);
}
/*
* Fetch some more rows from the node's cursor.
*/
static void
fetch_more_data(ForeignScanState *node)
{
PgFdwScanState *fsstate = (PgFdwScanState *) node->fdw_state;
PGresult *volatile res = NULL;
MemoryContext oldcontext;
/*
* We'll store the tuples in the batch_cxt. First, flush the previous
* batch.
*/
fsstate->tuples = NULL;
MemoryContextReset(fsstate->batch_cxt);
oldcontext = MemoryContextSwitchTo(fsstate->batch_cxt);
/* PGresult must be released before leaving this function. */
PG_TRY();
{
PGconn *conn = fsstate->conn;
char sql[64];
int fetch_size;
int numrows;
int i;
/* The fetch size is arbitrary, but shouldn't be enormous. */
fetch_size = 100;
snprintf(sql, sizeof(sql), "FETCH %d FROM c%u",
fetch_size, fsstate->cursor_number);
res = PQexec(conn, sql);
/* On error, report the original query, not the FETCH. */
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, fsstate->query);
/* Convert the data into HeapTuples */
numrows = PQntuples(res);
fsstate->tuples = (HeapTuple *) palloc0(numrows * sizeof(HeapTuple));
fsstate->num_tuples = numrows;
fsstate->next_tuple = 0;
for (i = 0; i < numrows; i++)
{
fsstate->tuples[i] =
make_tuple_from_result_row(res, i,
fsstate->rel,
fsstate->attinmeta,
fsstate->retrieved_attrs,
fsstate->temp_cxt);
}
/* Update fetch_ct_2 */
if (fsstate->fetch_ct_2 < 2)
fsstate->fetch_ct_2++;
/* Must be EOF if we didn't get as many tuples as we asked for. */
fsstate->eof_reached = (numrows < fetch_size);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
MemoryContextSwitchTo(oldcontext);
}
/*
* Force assorted GUC parameters to settings that ensure that we'll output
* data values in a form that is unambiguous to the remote server.
*
* This is rather expensive and annoying to do once per row, but there's
* little choice if we want to be sure values are transmitted accurately;
* we can't leave the settings in place between rows for fear of affecting
* user-visible computations.
*
* We use the equivalent of a function SET option to allow the settings to
* persist only until the caller calls reset_transmission_modes(). If an
* error is thrown in between, guc.c will take care of undoing the settings.
*
* The return value is the nestlevel that must be passed to
* reset_transmission_modes() to undo things.
*/
int
set_transmission_modes(void)
{
int nestlevel = NewGUCNestLevel();
/*
* The values set here should match what pg_dump does. See also
* configure_remote_session in connection.c.
*/
if (DateStyle != USE_ISO_DATES)
(void) set_config_option("datestyle", "ISO",
PGC_USERSET, PGC_S_SESSION,
GUC_ACTION_SAVE, true, 0);
if (IntervalStyle != INTSTYLE_POSTGRES)
(void) set_config_option("intervalstyle", "postgres",
PGC_USERSET, PGC_S_SESSION,
GUC_ACTION_SAVE, true, 0);
if (extra_float_digits < 3)
(void) set_config_option("extra_float_digits", "3",
PGC_USERSET, PGC_S_SESSION,
GUC_ACTION_SAVE, true, 0);
return nestlevel;
}
/*
* Undo the effects of set_transmission_modes().
*/
void
reset_transmission_modes(int nestlevel)
{
AtEOXact_GUC(true, nestlevel);
}
/*
* Utility routine to close a cursor.
*/
static void
close_cursor(PGconn *conn, unsigned int cursor_number)
{
char sql[64];
PGresult *res;
snprintf(sql, sizeof(sql), "CLOSE c%u", cursor_number);
/*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQexec(conn, sql);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, conn, true, sql);
PQclear(res);
}
/*
* prepare_foreign_modify
* Establish a prepared statement for execution of INSERT/UPDATE/DELETE
*/
static void
prepare_foreign_modify(PgFdwModifyState *fmstate)
{
char prep_name[NAMEDATALEN];
char *p_name;
PGresult *res;
/* Construct name we'll use for the prepared statement. */
snprintf(prep_name, sizeof(prep_name), "pgsql_fdw_prep_%u",
GetPrepStmtNumber(fmstate->conn));
p_name = pstrdup(prep_name);
/*
* We intentionally do not specify parameter types here, but leave the
* remote server to derive them by default. This avoids possible problems
* with the remote server using different type OIDs than we do. All of
* the prepared statements we use in this module are simple enough that
* the remote server will make the right choices.
*
* We don't use a PG_TRY block here, so be careful not to throw error
* without releasing the PGresult.
*/
res = PQprepare(fmstate->conn,
p_name,
fmstate->query,
0,
NULL);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, fmstate->conn, true, fmstate->query);
PQclear(res);
/* This action shows that the prepare has been done. */
fmstate->p_name = p_name;
}
/*
* convert_prep_stmt_params
* Create array of text strings representing parameter values
*
* tupleid is ctid to send, or NULL if none
* slot is slot to get remaining parameters from, or NULL if none
*
* Data is constructed in temp_cxt; caller should reset that after use.
*/
static const char **
convert_prep_stmt_params(PgFdwModifyState *fmstate,
ItemPointer tupleid,
TupleTableSlot *slot)
{
const char **p_values;
int pindex = 0;
MemoryContext oldcontext;
oldcontext = MemoryContextSwitchTo(fmstate->temp_cxt);
p_values = (const char **) palloc(sizeof(char *) * fmstate->p_nums);
/* 1st parameter should be ctid, if it's in use */
if (tupleid != NULL)
{
/* don't need set_transmission_modes for TID output */
p_values[pindex] = OutputFunctionCall(&fmstate->p_flinfo[pindex],
PointerGetDatum(tupleid));
pindex++;
}
/* get following parameters from slot */
if (slot != NULL && fmstate->target_attrs != NIL)
{
int nestlevel;
ListCell *lc;
nestlevel = set_transmission_modes();
foreach(lc, fmstate->target_attrs)
{
int attnum = lfirst_int(lc);
Datum value;
bool isnull;
value = slot_getattr(slot, attnum, &isnull);
if (isnull)
p_values[pindex] = NULL;
else
p_values[pindex] = OutputFunctionCall(&fmstate->p_flinfo[pindex],
value);
pindex++;
}
reset_transmission_modes(nestlevel);
}
Assert(pindex == fmstate->p_nums);
MemoryContextSwitchTo(oldcontext);
return p_values;
}
/*
* store_returning_result
* Store the result of a RETURNING clause
*
* On error, be sure to release the PGresult on the way out. Callers do not
* have PG_TRY blocks to ensure this happens.
*/
static void
store_returning_result(PgFdwModifyState *fmstate,
TupleTableSlot *slot, PGresult *res)
{
/* PGresult must be released before leaving this function. */
PG_TRY();
{
HeapTuple newtup;
newtup = make_tuple_from_result_row(res, 0,
fmstate->rel,
fmstate->attinmeta,
fmstate->retrieved_attrs,
fmstate->temp_cxt);
/* tuple will be deleted when it is cleared from the slot */
ExecStoreTuple(newtup, slot, InvalidBuffer, true);
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
}
/*
* postgresAnalyzeForeignTable
* Test whether analyzing this foreign table is supported
*/
static bool
postgresAnalyzeForeignTable(Relation relation,
AcquireSampleRowsFunc *func,
BlockNumber *totalpages)
{
ForeignTable *table;
ForeignServer *server;
UserMapping *user;
PGconn *conn;
StringInfoData sql;
PGresult *volatile res = NULL;
/* Return the row-analysis function pointer */
*func = postgresAcquireSampleRowsFunc;
/*
* Now we have to get the number of pages. It's annoying that the ANALYZE
* API requires us to return that now, because it forces some duplication
* of effort between this routine and postgresAcquireSampleRowsFunc. But
* it's probably not worth redefining that API at this point.
*/
/*
* Get the connection to use. We do the remote access as the table's
* owner, even if the ANALYZE was started by some other user.
*/
table = GetForeignTable(RelationGetRelid(relation));
server = GetForeignServer(table->serverid);
user = GetUserMapping(relation->rd_rel->relowner, server->serverid);
conn = GetConnection(server, user, false);
/*
* Construct command to get page count for relation.
*/
initStringInfo(&sql);
deparseAnalyzeSizeSql(&sql, relation);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
res = PQexec(conn, sql.data);
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, sql.data);
if (PQntuples(res) != 1 || PQnfields(res) != 1)
elog(ERROR, "unexpected result from deparseAnalyzeSizeSql query");
*totalpages = strtoul(PQgetvalue(res, 0, 0), NULL, 10);
PQclear(res);
res = NULL;
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
return true;
}
/*
* Acquire a random sample of rows from foreign table managed by postgres_fdw.
*
* We fetch the whole table from the remote side and pick out some sample rows.
*
* Selected rows are returned in the caller-allocated array rows[],
* which must have at least targrows entries.
* The actual number of rows selected is returned as the function result.
* We also count the total number of rows in the table and return it into
* *totalrows. Note that *totaldeadrows is always set to 0.
*
* Note that the returned list of rows is not always in order by physical
* position in the table. Therefore, correlation estimates derived later
* may be meaningless, but it's OK because we don't use the estimates
* currently (the planner only pays attention to correlation for indexscans).
*/
static int
postgresAcquireSampleRowsFunc(Relation relation, int elevel,
HeapTuple *rows, int targrows,
double *totalrows,
double *totaldeadrows)
{
PgFdwAnalyzeState astate;
ForeignTable *table;
ForeignServer *server;
UserMapping *user;
PGconn *conn;
unsigned int cursor_number;
StringInfoData sql;
PGresult *volatile res = NULL;
/* Initialize workspace state */
astate.rel = relation;
astate.attinmeta = TupleDescGetAttInMetadata(RelationGetDescr(relation));
astate.rows = rows;
astate.targrows = targrows;
astate.numrows = 0;
astate.samplerows = 0;
astate.rowstoskip = -1; /* -1 means not set yet */
astate.rstate = anl_init_selection_state(targrows);
/* Remember ANALYZE context, and create a per-tuple temp context */
astate.anl_cxt = CurrentMemoryContext;
astate.temp_cxt = AllocSetContextCreate(CurrentMemoryContext,
"postgres_fdw temporary data",
ALLOCSET_SMALL_MINSIZE,
ALLOCSET_SMALL_INITSIZE,
ALLOCSET_SMALL_MAXSIZE);
/*
* Get the connection to use. We do the remote access as the table's
* owner, even if the ANALYZE was started by some other user.
*/
table = GetForeignTable(RelationGetRelid(relation));
server = GetForeignServer(table->serverid);
user = GetUserMapping(relation->rd_rel->relowner, server->serverid);
conn = GetConnection(server, user, false);
/*
* Construct cursor that retrieves whole rows from remote.
*/
cursor_number = GetCursorNumber(conn);
initStringInfo(&sql);
appendStringInfo(&sql, "DECLARE c%u CURSOR FOR ", cursor_number);
deparseAnalyzeSql(&sql, relation, &astate.retrieved_attrs);
/* In what follows, do not risk leaking any PGresults. */
PG_TRY();
{
res = PQexec(conn, sql.data);
if (PQresultStatus(res) != PGRES_COMMAND_OK)
pgfdw_report_error(ERROR, res, conn, false, sql.data);
PQclear(res);
res = NULL;
/* Retrieve and process rows a batch at a time. */
for (;;)
{
char fetch_sql[64];
int fetch_size;
int numrows;
int i;
/* Allow users to cancel long query */
CHECK_FOR_INTERRUPTS();
/*
* XXX possible future improvement: if rowstoskip is large, we
* could issue a MOVE rather than physically fetching the rows,
* then just adjust rowstoskip and samplerows appropriately.
*/
/* The fetch size is arbitrary, but shouldn't be enormous. */
fetch_size = 100;
/* Fetch some rows */
snprintf(fetch_sql, sizeof(fetch_sql), "FETCH %d FROM c%u",
fetch_size, cursor_number);
res = PQexec(conn, fetch_sql);
/* On error, report the original query, not the FETCH. */
if (PQresultStatus(res) != PGRES_TUPLES_OK)
pgfdw_report_error(ERROR, res, conn, false, sql.data);
/* Process whatever we got. */
numrows = PQntuples(res);
for (i = 0; i < numrows; i++)
analyze_row_processor(res, i, &astate);
PQclear(res);
res = NULL;
/* Must be EOF if we didn't get all the rows requested. */
if (numrows < fetch_size)
break;
}
/* Close the cursor, just to be tidy. */
close_cursor(conn, cursor_number);
}
PG_CATCH();
{
if (res)
PQclear(res);
PG_RE_THROW();
}
PG_END_TRY();
ReleaseConnection(conn);
/* We assume that we have no dead tuple. */
*totaldeadrows = 0.0;
/* We've retrieved all living tuples from foreign server. */
*totalrows = astate.samplerows;
/*
* Emit some interesting relation info
*/
ereport(elevel,
(errmsg("\"%s\": table contains %.0f rows, %d rows in sample",
RelationGetRelationName(relation),
astate.samplerows, astate.numrows)));
return astate.numrows;
}
/*
* Collect sample rows from the result of query.
* - Use all tuples in sample until target # of samples are collected.
* - Subsequently, replace already-sampled tuples randomly.
*/
static void
analyze_row_processor(PGresult *res, int row, PgFdwAnalyzeState *astate)
{
int targrows = astate->targrows;
int pos; /* array index to store tuple in */
MemoryContext oldcontext;
/* Always increment sample row counter. */
astate->samplerows += 1;
/*
* Determine the slot where this sample row should be stored. Set pos to
* negative value to indicate the row should be skipped.
*/
if (astate->numrows < targrows)
{
/* First targrows rows are always included into the sample */
pos = astate->numrows++;
}
else
{
/*
* Now we start replacing tuples in the sample until we reach the end
* of the relation. Same algorithm as in acquire_sample_rows in
* analyze.c; see Jeff Vitter's paper.
*/
if (astate->rowstoskip < 0)
astate->rowstoskip = anl_get_next_S(astate->samplerows, targrows,
&astate->rstate);
if (astate->rowstoskip <= 0)
{
/* Choose a random reservoir element to replace. */
pos = (int) (targrows * anl_random_fract());
Assert(pos >= 0 && pos < targrows);
heap_freetuple(astate->rows[pos]);
}
else
{
/* Skip this tuple. */
pos = -1;
}
astate->rowstoskip -= 1;
}
if (pos >= 0)
{
/*
* Create sample tuple from current result row, and store it in the
* position determined above. The tuple has to be created in anl_cxt.
*/
oldcontext = MemoryContextSwitchTo(astate->anl_cxt);
astate->rows[pos] = make_tuple_from_result_row(res, row,
astate->rel,
astate->attinmeta,
astate->retrieved_attrs,
astate->temp_cxt);
MemoryContextSwitchTo(oldcontext);
}
}
/*
* Create a tuple from the specified row of the PGresult.
*
* rel is the local representation of the foreign table, attinmeta is
* conversion data for the rel's tupdesc, and retrieved_attrs is an
* integer list of the table column numbers present in the PGresult.
* temp_context is a working context that can be reset after each tuple.
*/
static HeapTuple
make_tuple_from_result_row(PGresult *res,
int row,
Relation rel,
AttInMetadata *attinmeta,
List *retrieved_attrs,
MemoryContext temp_context)
{
HeapTuple tuple;
TupleDesc tupdesc = RelationGetDescr(rel);
Datum *values;
bool *nulls;
ItemPointer ctid = NULL;
ConversionLocation errpos;
ErrorContextCallback errcallback;
MemoryContext oldcontext;
ListCell *lc;
int j;
Assert(row < PQntuples(res));
/*
* Do the following work in a temp context that we reset after each tuple.
* This cleans up not only the data we have direct access to, but any
* cruft the I/O functions might leak.
*/
oldcontext = MemoryContextSwitchTo(temp_context);
values = (Datum *) palloc0(tupdesc->natts * sizeof(Datum));
nulls = (bool *) palloc(tupdesc->natts * sizeof(bool));
/* Initialize to nulls for any columns not present in result */
memset(nulls, true, tupdesc->natts * sizeof(bool));
/*
* Set up and install callback to report where conversion error occurs.
*/
errpos.rel = rel;
errpos.cur_attno = 0;
errcallback.callback = conversion_error_callback;
errcallback.arg = (void *) &errpos;
errcallback.previous = error_context_stack;
error_context_stack = &errcallback;
/*
* i indexes columns in the relation, j indexes columns in the PGresult.
*/
j = 0;
foreach(lc, retrieved_attrs)
{
int i = lfirst_int(lc);
char *valstr;
/* fetch next column's textual value */
if (PQgetisnull(res, row, j))
valstr = NULL;
else
valstr = PQgetvalue(res, row, j);
/* convert value to internal representation */
if (i > 0)
{
/* ordinary column */
Assert(i <= tupdesc->natts);
nulls[i - 1] = (valstr == NULL);
/* Apply the input function even to nulls, to support domains */
errpos.cur_attno = i;
values[i - 1] = InputFunctionCall(&attinmeta->attinfuncs[i - 1],
valstr,
attinmeta->attioparams[i - 1],
attinmeta->atttypmods[i - 1]);
errpos.cur_attno = 0;
}
else if (i == SelfItemPointerAttributeNumber)
{
/* ctid --- note we ignore any other system column in result */
if (valstr != NULL)
{
Datum datum;
datum = DirectFunctionCall1(tidin, CStringGetDatum(valstr));
ctid = (ItemPointer) DatumGetPointer(datum);
}
}
j++;
}
/* Uninstall error context callback. */
error_context_stack = errcallback.previous;
/*
* Check we got the expected number of columns. Note: j == 0 and
* PQnfields == 1 is expected, since deparse emits a NULL if no columns.
*/
if (j > 0 && j != PQnfields(res))
elog(ERROR, "remote query result does not match the foreign table");
/*
* Build the result tuple in caller's memory context.
*/
MemoryContextSwitchTo(oldcontext);
tuple = heap_form_tuple(tupdesc, values, nulls);
if (ctid)
tuple->t_self = *ctid;
/* Clean up */
MemoryContextReset(temp_context);
return tuple;
}
/*
* Callback function which is called when error occurs during column value
* conversion. Print names of column and relation.
*/
static void
conversion_error_callback(void *arg)
{
ConversionLocation *errpos = (ConversionLocation *) arg;
TupleDesc tupdesc = RelationGetDescr(errpos->rel);
if (errpos->cur_attno > 0 && errpos->cur_attno <= tupdesc->natts)
errcontext("column \"%s\" of foreign table \"%s\"",
NameStr(tupdesc->attrs[errpos->cur_attno - 1]->attname),
RelationGetRelationName(errpos->rel));
}