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Teach the planner to treat a partial unique index as proving a variable is

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unique for a particular query, if the index predicate is satisfied.  This
requires a bit of reordering of operations so that we check the predicates
before doing any selectivity estimates, but shouldn't really cause any
noticeable slowdown.  Per a comment from Michal Politowski.
This commit is contained in:
Tom Lane
2009-02-15 20:16:21 +00:00
parent 57b5984d24
commit ce6e31de9c
5 changed files with 70 additions and 39 deletions
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16
src/backend/optimizer/path/allpaths.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.179 2009/01/01 17:23:43 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/allpaths.c,v 1.180 2009/02/15 20:16:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -225,19 +225,25 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
return;
}
/*
* Test any partial indexes of rel for applicability. We must do this
* first since partial unique indexes can affect size estimates.
*/
check_partial_indexes(root, rel);
/* Mark rel with estimated output rows, width, etc */
set_baserel_size_estimates(root, rel);
/* Test any partial indexes of rel for applicability */
check_partial_indexes(root, rel);
/*
* Check to see if we can extract any restriction conditions from join
* quals that are OR-of-AND structures. If so, add them to the rel's
* restriction list, and recompute the size estimates.
* restriction list, and redo the above steps.
*/
if (create_or_index_quals(root, rel))
{
check_partial_indexes(root, rel);
set_baserel_size_estimates(root, rel);
}
/*
* Generate paths and add them to the rel's pathlist.

13
src/backend/optimizer/path/indxpath.c
View File

@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.235 2009/01/01 17:23:43 momjian Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/indxpath.c,v 1.236 2009/02/15 20:16:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1367,8 +1367,12 @@ match_rowcompare_to_indexcol(IndexOptInfo *index,
/*
* check_partial_indexes
* Check each partial index of the relation, and mark it predOK or not
* depending on whether the predicate is satisfied for this query.
* Check each partial index of the relation, and mark it predOK if
* the index's predicate is satisfied for this query.
*
* Note: it is possible for this to get re-run after adding more restrictions
* to the rel; so we might be able to prove more indexes OK. We assume that
* adding more restrictions can't make an index not OK.
*/
void
check_partial_indexes(PlannerInfo *root, RelOptInfo *rel)
@@ -1383,6 +1387,9 @@ check_partial_indexes(PlannerInfo *root, RelOptInfo *rel)
if (index->indpred == NIL)
continue; /* ignore non-partial indexes */
if (index->predOK)
continue; /* don't repeat work if already proven OK */
index->predOK = predicate_implied_by(index->indpred,
restrictinfo_list);
}

4
src/backend/optimizer/path/orindxpath.c
View File

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/path/orindxpath.c,v 1.87 2009/02/06 23:43:23 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/path/orindxpath.c,v 1.88 2009/02/15 20:16:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -181,6 +181,6 @@ create_or_index_quals(PlannerInfo *root, RelOptInfo *rel)
/* It isn't an outer join clause, so no need to adjust outer_selec */
}
/* Tell caller to recompute rel's rows estimate */
/* Tell caller to recompute partial index status and rowcount estimate */
return true;
}

13
src/backend/optimizer/util/plancat.c
View File

@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.154 2009/01/07 22:40:49 tgl Exp $
* $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.155 2009/02/15 20:16:21 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -939,15 +939,16 @@ has_unique_index(RelOptInfo *rel, AttrNumber attno)
/*
* Note: ignore partial indexes, since they don't allow us to conclude
* that all attr values are distinct. We don't take any interest in
* expressional indexes either. Also, a multicolumn unique index
* doesn't allow us to conclude that just the specified attr is
* unique.
* that all attr values are distinct, *unless* they are marked predOK
* which means we know the index's predicate is satisfied by the query.
* We don't take any interest in expressional indexes either. Also, a
* multicolumn unique index doesn't allow us to conclude that just the
* specified attr is unique.
*/
if (index->unique &&
index->ncolumns == 1 &&
index->indexkeys[0] == attno &&
index->indpred == NIL)
(index->indpred == NIL || index->predOK))
return true;
}
return false;