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Tighten coding in new_join_pathkey, which seems to be a hotspot

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for GEQO ...
This commit is contained in:
Tom Lane 1999-05-17 00:26:33 +00:00
parent 1332c1e144
commit 0b8b1fe3aa
1 changed files with 53 additions and 96 deletions
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149
src/backend/optimizer/path/pathkeys.c
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@ -7,7 +7,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.8 1999/04/30 03:59:06 tgl Exp $ * $Header: /cvsroot/pgsql/src/backend/optimizer/path/pathkeys.c,v 1.9 1999/05/17 00:26:33 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -29,30 +29,34 @@ static int match_pathkey_joinkeys(List *pathkey, List *joinkeys,
int outer_or_inner); int outer_or_inner);
static List *new_join_pathkey(List *pathkeys, List *join_rel_tlist, static List *new_join_pathkey(List *pathkeys, List *join_rel_tlist,
List *joinclauses); List *joinclauses);
static List *get_joinvars_for_var(Var *pathkey, List **considered_pathkeys,
List *join_rel_tlist, List *joinclauses);
/* /*--------------------
* Explanation of Path.pathkeys * Explanation of Path.pathkeys
* *
* Path.pathkeys is a List of List of Var nodes that represent the sort * Path.pathkeys is a List of List of Var nodes that represent the sort
* order of the result generated by the Path. * order of the result generated by the Path.
* *
* In single/base relation RelOptInfo's, the Path's represent various ways * In single/base relation RelOptInfo's, the Path's represent various ways
* of generate the relation. Sequential scan Paths have a NIL pathkeys. * of generating the relation and the resulting ordering of the tuples.
* Index scans have Path.pathkeys that represent the chosen index. A * Sequential scan Paths have NIL pathkeys, indicating no known ordering.
* single-key index pathkeys would be { {tab1_indexkey1} }. The pathkeys * Index scans have Path.pathkeys that represent the chosen index.
* entry for a multi-key index would be { {tab1_indexkey1}, {tab1_indexkey2} }. * A single-key index pathkeys would be { {tab1_indexkey1} }. For a
* multi-key index pathkeys would be { {tab1_indexkey1}, {tab1_indexkey2} },
* indicating major sort by indexkey1 and minor sort by indexkey2.
* *
* Multi-relation RelOptInfo Path's are more complicated. Mergejoins are * Multi-relation RelOptInfo Path's are more complicated. Mergejoins are
* only performed with equajoins("="). Because of this, the multi-relation * only performed with equijoins ("="). Because of this, the multi-relation
* path actually has more than one primary Var key. For example, a * path actually has more than one primary Var key. For example, a
* mergejoin Path of "tab1.col1 = tab2.col1" would generate a pathkeys of * mergejoin Path of "tab1.col1 = tab2.col1" would generate a pathkeys of
* { {tab1.col1, tab2.col1} }. This allows future joins to use either Var * { {tab1.col1, tab2.col1} }, indicating that the major sort order of the
* as a pre-sorted key to prevent Mergejoins from having to re-sort the Path. * Path can be taken to be *either* tab1.col1 or tab2.col1.
* They are equal, so they are both primary sort keys. This is why pathkeys * They are equal, so they are both primary sort keys. This allows future
* is a List of Lists. * joins to use either Var as a pre-sorted key to prevent upper Mergejoins
* from having to re-sort the Path. This is why pathkeys is a List of Lists.
*
* Note that while the order of the top list is meaningful (primary vs.
* secondary sort key), the order of each sublist is arbitrary.
* *
* For multi-key sorts, if the outer is sorted by a multi-key index, the * For multi-key sorts, if the outer is sorted by a multi-key index, the
* multi-key index remains after the join. If the inner has a multi-key * multi-key index remains after the join. If the inner has a multi-key
@ -60,11 +64,16 @@ static List *get_joinvars_for_var(Var *pathkey, List **considered_pathkeys,
* Mergejoins only join on the primary key. Currently, non-primary keys * Mergejoins only join on the primary key. Currently, non-primary keys
* in the pathkeys List are of limited value. * in the pathkeys List are of limited value.
* *
* HashJoin has similar functionality. NestJoin does not perform sorting, * Although Hashjoins also work only with equijoin operators, it is *not*
* and allows non-equajoins, so it does not allow useful pathkeys. * safe to consider the output of a Hashjoin to be sorted in any particular
* order --- not even the outer path's order. This is true because the
* executor might have to split the join into multiple batches.
*
* NestJoin does not perform sorting, and allows non-equijoins, so it does
* not allow useful pathkeys. (But couldn't we use the outer path's order?)
* *
* -- bjm * -- bjm
* *--------------------
*/ */
/**************************************************************************** /****************************************************************************
@ -228,7 +237,7 @@ get_cheapest_path_for_joinkeys(List *joinkeys,
int outer_or_inner) int outer_or_inner)
{ {
Path *matched_path = NULL; Path *matched_path = NULL;
List *i = NIL; List *i;
foreach(i, paths) foreach(i, paths)
{ {
@ -337,16 +346,16 @@ new_join_pathkeys(List *outer_pathkeys,
List *join_rel_tlist, List *join_rel_tlist,
List *joinclauses) List *joinclauses)
{ {
List *outer_pathkey = NIL;
List *final_pathkeys = NIL; List *final_pathkeys = NIL;
List *new_pathkey; List *i;
List *i = NIL;
foreach(i, outer_pathkeys) foreach(i, outer_pathkeys)
{ {
outer_pathkey = lfirst(i); List *outer_pathkey = lfirst(i);
List *new_pathkey;
new_pathkey = new_join_pathkey(outer_pathkey, join_rel_tlist, new_pathkey = new_join_pathkey(outer_pathkey, join_rel_tlist,
joinclauses); joinclauses);
if (new_pathkey != NIL) if (new_pathkey != NIL)
final_pathkeys = lappend(final_pathkeys, new_pathkey); final_pathkeys = lappend(final_pathkeys, new_pathkey);
} }
@ -355,19 +364,18 @@ new_join_pathkeys(List *outer_pathkeys,
/* /*
* new_join_pathkey * new_join_pathkey
* Finds new vars that become pathkeys due to qualification clauses that * Generate an individual pathkey sublist, consisting of the outer vars
* contain any previously considered pathkeys. These new pathkeys plus the * already mentioned in 'pathkey' plus any inner vars that are joined to
* pathkeys from 'pathkeys' form a new pathkey for the join relation. * them (and thus can now also be considered path keys, per discussion
* at the top of this file).
* *
* Note that each returned pathkey is the var node found in * Note that each returned pathkey is the var node found in
* 'join_rel_tlist' rather than the joinclause var node. * 'join_rel_tlist' rather than the joinclause var node.
* (Is this important?) Also, we return a fully copied list
* that does not share any subnodes with existing data structures.
* (Is that important, either?)
* *
* 'pathkeys' is a list of pathkeys for which matching pathkeys are to be * Returns a new pathkey (list of pathkey variables).
* found
* 'considered_pathkeys' is the current list of all pathkeys corresponding
* to a given pathkey
*
* Returns a new pathkey(list of pathkeys).
* *
*/ */
static List * static List *
@ -375,84 +383,33 @@ new_join_pathkey(List *pathkey,
List *join_rel_tlist, List *join_rel_tlist,
List *joinclauses) List *joinclauses)
{ {
List *final_pathkey = NIL; List *new_pathkey = NIL;
List *i = NIL; List *i,
List *considered_pathkeys = NIL; *j;
foreach(i, pathkey) foreach(i, pathkey)
{ {
Var *key = (Var *) lfirst(i); Var *key = (Var *) lfirst(i);
List *joined_keys;
Expr *tlist_key; Expr *tlist_key;
Assert(key); Assert(key);
joined_keys = get_joinvars_for_var(key, &considered_pathkeys,
join_rel_tlist, joinclauses);
if (joined_keys)
{
considered_pathkeys = nconc(considered_pathkeys, joined_keys);
final_pathkey = nconc(final_pathkey, joined_keys);
}
tlist_key = matching_tlist_var(key, join_rel_tlist); tlist_key = matching_tlist_var(key, join_rel_tlist);
if (tlist_key && !member(tlist_key, considered_pathkeys)) if (tlist_key && !member(tlist_key, new_pathkey))
new_pathkey = lcons(copyObject(tlist_key), new_pathkey);
foreach(j, joinclauses)
{ {
/* Expr *joinclause = lfirst(j);
* If pathkey is in the target list, and not considered, Expr *tlist_other_var;
* add it
*/
considered_pathkeys = lcons(tlist_key, considered_pathkeys);
final_pathkey = lcons(tlist_key, final_pathkey);
}
}
return copyObject(final_pathkey);
}
/* tlist_other_var = matching_tlist_var(
* get_joinvars_for_var
* Returns a list of new pathkeys:
* (1) which are not listed in 'considered_pathkeys'
* (2) for which the "other" variable in some clause in 'joinclauses' is
* 'pathkey'
* (3) which are mentioned in 'join_rel_tlist'
*
* Note that each returned pathkey is the var node found in
* 'join_rel_tlist' rather than the joinclause var node.
*
* 'pathkey' is the var node for which we are trying to find matching
* clauses
*
* Returns a list of new pathkeys.
*
*/
static List *
get_joinvars_for_var(Var *key,
List **considered_pathkeys,
List *join_rel_tlist,
List *joinclauses)
{
List *final_pathkey = NIL;
Expr *joinclause;
List *i;
Expr *tlist_other_var;
foreach(i, joinclauses)
{
joinclause = lfirst(i);
tlist_other_var = matching_tlist_var(
other_join_clause_var(key, joinclause), other_join_clause_var(key, joinclause),
join_rel_tlist); join_rel_tlist);
if (tlist_other_var && if (tlist_other_var && !member(tlist_other_var, new_pathkey))
!member(tlist_other_var, *considered_pathkeys)) new_pathkey = lcons(copyObject(tlist_other_var), new_pathkey);
{
/*
* The key has a join variable that is in the target list,
* and has not been considered.
*/
*considered_pathkeys = lcons(tlist_other_var, *considered_pathkeys);
final_pathkey = lcons(tlist_other_var, final_pathkey);
} }
} }
return final_pathkey;
return new_pathkey;
} }