*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.105 2010/02/26 02:00:45 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/path/joinrels.c,v 1.106 2010/09/14 23:15:29 tgl Exp $
*
*-------------------------------------------------------------------------
*/
static bool has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel);
static bool is_dummy_rel(RelOptInfo *rel);
static void mark_dummy_rel(RelOptInfo *rel);
-static bool restriction_is_constant_false(List *restrictlist);
+static bool restriction_is_constant_false(List *restrictlist,
+ bool only_pushed_down);
/*
*
* Also, a provably constant-false join restriction typically means that
* we can skip evaluating one or both sides of the join. We do this by
- * marking the appropriate rel as dummy.
+ * marking the appropriate rel as dummy. For outer joins, a constant-false
+ * restriction that is pushed down still means the whole join is dummy,
+ * while a non-pushed-down one means that no inner rows will join so we
+ * can treat the inner rel as dummy.
*
* We need only consider the jointypes that appear in join_info_list, plus
* JOIN_INNER.
{
case JOIN_INNER:
if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
- restriction_is_constant_false(restrictlist))
+ restriction_is_constant_false(restrictlist, false))
{
mark_dummy_rel(joinrel);
break;
restrictlist);
break;
case JOIN_LEFT:
- if (is_dummy_rel(rel1))
+ if (is_dummy_rel(rel1) ||
+ restriction_is_constant_false(restrictlist, true))
{
mark_dummy_rel(joinrel);
break;
}
- if (restriction_is_constant_false(restrictlist) &&
+ if (restriction_is_constant_false(restrictlist, false) &&
bms_is_subset(rel2->relids, sjinfo->syn_righthand))
mark_dummy_rel(rel2);
add_paths_to_joinrel(root, joinrel, rel1, rel2,
restrictlist);
break;
case JOIN_FULL:
- if (is_dummy_rel(rel1) && is_dummy_rel(rel2))
+ if ((is_dummy_rel(rel1) && is_dummy_rel(rel2)) ||
+ restriction_is_constant_false(restrictlist, true))
{
mark_dummy_rel(joinrel);
break;
bms_is_subset(sjinfo->min_righthand, rel2->relids))
{
if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
- restriction_is_constant_false(restrictlist))
+ restriction_is_constant_false(restrictlist, false))
{
mark_dummy_rel(joinrel);
break;
create_unique_path(root, rel2, rel2->cheapest_total_path,
sjinfo) != NULL)
{
+ if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
+ restriction_is_constant_false(restrictlist, false))
+ {
+ mark_dummy_rel(joinrel);
+ break;
+ }
add_paths_to_joinrel(root, joinrel, rel1, rel2,
JOIN_UNIQUE_INNER, sjinfo,
restrictlist);
}
break;
case JOIN_ANTI:
- if (is_dummy_rel(rel1))
+ if (is_dummy_rel(rel1) ||
+ restriction_is_constant_false(restrictlist, true))
{
mark_dummy_rel(joinrel);
break;
}
- if (restriction_is_constant_false(restrictlist) &&
+ if (restriction_is_constant_false(restrictlist, false) &&
bms_is_subset(rel2->relids, sjinfo->syn_righthand))
mark_dummy_rel(rel2);
add_paths_to_joinrel(root, joinrel, rel1, rel2,
* join situations this will leave us computing cartesian products only to
* decide there's no match for an outer row, which is pretty stupid. So,
* we need to detect the case.
+ *
+ * If only_pushed_down is TRUE, then consider only pushed-down quals.
*/
static bool
-restriction_is_constant_false(List *restrictlist)
+restriction_is_constant_false(List *restrictlist, bool only_pushed_down)
{
ListCell *lc;
RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
Assert(IsA(rinfo, RestrictInfo));
+ if (only_pushed_down && !rinfo->is_pushed_down)
+ continue;
+
if (rinfo->clause && IsA(rinfo->clause, Const))
{
Const *con = (Const *) rinfo->clause;
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/plan/analyzejoins.c,v 1.3 2010/07/06 19:18:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/plan/analyzejoins.c,v 1.4 2010/09/14 23:15:29 tgl Exp $
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
+#include "optimizer/joininfo.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
/* local functions */
static bool join_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo);
-static void remove_rel_from_query(PlannerInfo *root, int relid);
+static void remove_rel_from_query(PlannerInfo *root, int relid,
+ Relids joinrelids);
static List *remove_rel_from_joinlist(List *joinlist, int relid, int *nremoved);
*/
innerrelid = bms_singleton_member(sjinfo->min_righthand);
- remove_rel_from_query(root, innerrelid);
+ remove_rel_from_query(root, innerrelid,
+ bms_union(sjinfo->min_lefthand,
+ sjinfo->min_righthand));
/* We verify that exactly one reference gets removed from joinlist */
nremoved = 0;
{
RestrictInfo *restrictinfo = (RestrictInfo *) lfirst(l);
- /* Ignore clauses not pertinent to this join */
- if (!bms_is_subset(restrictinfo->required_relids, joinrelids))
- continue;
-
/*
- * If we find a pushed-down clause, it must have come from above the
- * outer join and it must contain references to the inner rel. (If it
- * had only outer-rel variables, it'd have been pushed down into the
- * outer rel.) Therefore, we can conclude that join removal is unsafe
- * without any examination of the clause contents.
+ * If it's not a join clause for this outer join, we can't use it.
+ * Note that if the clause is pushed-down, then it is logically from
+ * above the outer join, even if it references no other rels (it might
+ * be from WHERE, for example).
*/
- if (restrictinfo->is_pushed_down)
- return false;
+ if (restrictinfo->is_pushed_down ||
+ !bms_equal(restrictinfo->required_relids, joinrelids))
+ {
+ /*
+ * If such a clause actually references the inner rel then
+ * join removal has to be disallowed. We have to check this
+ * despite the previous attr_needed checks because of the
+ * possibility of pushed-down clauses referencing the rel.
+ */
+ if (bms_is_member(innerrelid, restrictinfo->clause_relids))
+ return false;
+ continue; /* else, ignore; not useful here */
+ }
/* Ignore if it's not a mergejoinable clause */
if (!restrictinfo->can_join ||
* We are not terribly thorough here. We must make sure that the rel is
* no longer treated as a baserel, and that attributes of other baserels
* are no longer marked as being needed at joins involving this rel.
- * In particular, we don't bother removing join quals involving the rel from
- * the joininfo lists; they'll just get ignored, since we will never form a
- * join relation at which they could be evaluated.
+ * Also, join quals involving the rel have to be removed from the joininfo
+ * lists, but only if they belong to the outer join identified by joinrelids.
*/
static void
-remove_rel_from_query(PlannerInfo *root, int relid)
+remove_rel_from_query(PlannerInfo *root, int relid, Relids joinrelids)
{
RelOptInfo *rel = find_base_rel(root, relid);
+ List *joininfos;
Index rti;
ListCell *l;
phinfo->ph_needed = bms_del_member(phinfo->ph_needed, relid);
}
+
+ /*
+ * Remove any joinquals referencing the rel from the joininfo lists.
+ *
+ * In some cases, a joinqual has to be put back after deleting its
+ * reference to the target rel. This can occur for pseudoconstant and
+ * outerjoin-delayed quals, which can get marked as requiring the rel in
+ * order to force them to be evaluated at or above the join. We can't
+ * just discard them, though. Only quals that logically belonged to the
+ * outer join being discarded should be removed from the query.
+ *
+ * We must make a copy of the rel's old joininfo list before starting the
+ * loop, because otherwise remove_join_clause_from_rels would destroy the
+ * list while we're scanning it.
+ */
+ joininfos = list_copy(rel->joininfo);
+ foreach(l, joininfos)
+ {
+ RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
+
+ remove_join_clause_from_rels(root, rinfo, rinfo->required_relids);
+
+ if (rinfo->is_pushed_down ||
+ !bms_equal(rinfo->required_relids, joinrelids))
+ {
+ /* Recheck that qual doesn't actually reference the target rel */
+ Assert(!bms_is_member(relid, rinfo->clause_relids));
+ /*
+ * The required_relids probably aren't shared with anything else,
+ * but let's copy them just to be sure.
+ */
+ rinfo->required_relids = bms_copy(rinfo->required_relids);
+ rinfo->required_relids = bms_del_member(rinfo->required_relids,
+ relid);
+ distribute_restrictinfo_to_rels(root, rinfo);
+ }
+ }
}
/*
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/optimizer/util/joininfo.c,v 1.52 2010/01/02 16:57:48 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/optimizer/util/joininfo.c,v 1.53 2010/09/14 23:15:29 tgl Exp $
*
*-------------------------------------------------------------------------
*/
}
bms_free(tmprelids);
}
+
+/*
+ * remove_join_clause_from_rels
+ * Delete 'restrictinfo' from all the joininfo lists it is in
+ *
+ * This reverses the effect of add_join_clause_to_rels. It's used when we
+ * discover that a relation need not be joined at all.
+ *
+ * 'restrictinfo' describes the join clause
+ * 'join_relids' is the list of relations participating in the join clause
+ * (there must be more than one)
+ */
+void
+remove_join_clause_from_rels(PlannerInfo *root,
+ RestrictInfo *restrictinfo,
+ Relids join_relids)
+{
+ Relids tmprelids;
+ int cur_relid;
+
+ tmprelids = bms_copy(join_relids);
+ while ((cur_relid = bms_first_member(tmprelids)) >= 0)
+ {
+ RelOptInfo *rel = find_base_rel(root, cur_relid);
+
+ /*
+ * Remove the restrictinfo from the list. Pointer comparison is
+ * sufficient.
+ */
+ Assert(list_member_ptr(rel->joininfo, restrictinfo));
+ rel->joininfo = list_delete_ptr(rel->joininfo, restrictinfo);
+ }
+ bms_free(tmprelids);
+}
* Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/optimizer/joininfo.h,v 1.38 2010/01/02 16:58:07 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/optimizer/joininfo.h,v 1.39 2010/09/14 23:15:29 tgl Exp $
*
*-------------------------------------------------------------------------
*/
extern void add_join_clause_to_rels(PlannerInfo *root,
RestrictInfo *restrictinfo,
Relids join_relids);
+extern void remove_join_clause_from_rels(PlannerInfo *root,
+ RestrictInfo *restrictinfo,
+ Relids join_relids);
#endif /* JOININFO_H */
-> Seq Scan on child c
(5 rows)
+-- check for a 9.0rc1 bug: join removal breaks pseudoconstant qual handling
+select p.* from
+ parent p left join child c on (p.k = c.k)
+ where p.k = 1 and p.k = 2;
+ k | pd
+---+----
+(0 rows)
+
+explain (costs off)
+select p.* from
+ parent p left join child c on (p.k = c.k)
+ where p.k = 1 and p.k = 2;
+ QUERY PLAN
+------------------------------------------------
+ Result
+ One-Time Filter: false
+ -> Index Scan using parent_pkey on parent p
+ Index Cond: (k = 1)
+(4 rows)
+
+select p.* from
+ (parent p left join child c on (p.k = c.k)) join parent x on p.k = x.k
+ where p.k = 1 and p.k = 2;
+ k | pd
+---+----
+(0 rows)
+
+explain (costs off)
+select p.* from
+ (parent p left join child c on (p.k = c.k)) join parent x on p.k = x.k
+ where p.k = 1 and p.k = 2;
+ QUERY PLAN
+--------------------------
+ Result
+ One-Time Filter: false
+(2 rows)
+
-- bug 5255: this is not optimizable by join removal
begin;
CREATE TEMP TABLE a (id int PRIMARY KEY);
left join (select c.*, true as linked from child c) as ss
on (p.k = ss.k);
+-- check for a 9.0rc1 bug: join removal breaks pseudoconstant qual handling
+select p.* from
+ parent p left join child c on (p.k = c.k)
+ where p.k = 1 and p.k = 2;
+explain (costs off)
+select p.* from
+ parent p left join child c on (p.k = c.k)
+ where p.k = 1 and p.k = 2;
+
+select p.* from
+ (parent p left join child c on (p.k = c.k)) join parent x on p.k = x.k
+ where p.k = 1 and p.k = 2;
+explain (costs off)
+select p.* from
+ (parent p left join child c on (p.k = c.k)) join parent x on p.k = x.k
+ where p.k = 1 and p.k = 2;
+
-- bug 5255: this is not optimizable by join removal
begin;
projects / postgresql.git / commitdiff