Change more places to be less trusting of RestrictInfo.is_pushed_down.

On further reflection, commit e5d83995e didn't go far enough: pretty much
everywhere in the planner that examines a clause's is_pushed_down flag
ought to be changed to use the more complicated behavior where we also
check the clause's required_relids.  Otherwise we could make incorrect
decisions about whether, say, a clause is safe to use as a hash clause.

Some (many?) of these places are safe as-is, either because they are
never reached while considering a parameterized path, or because there
are additional checks that would reject a pushed-down clause anyway.
However, it seems smarter to just code them all the same way rather
than rely on easily-broken reasoning of that sort.

In support of that, invent a new macro RINFO_IS_PUSHED_DOWN that should
be used in place of direct tests on the is_pushed_down flag.

Like the previous patch, back-patch to all supported branches.

Discussion: https://postgr.es/m/f8128b11-c5bf-3539-48cd-234178b2314d@proxel.se

diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index b653187a7726651f03a23a50640da8b01487f7fe..d8ae029faa9af0e8f8e3b39918b57a922d268841 100644 (file)
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -4127,7 +4127,8 @@ foreign_join_ok(PlannerInfo *root, RelOptInfo *joinrel, JoinType jointype,
        bool        is_remote_clause = is_foreign_expr(root, joinrel,
                                                       rinfo->clause);
 
-       if (IS_OUTER_JOIN(jointype) && !rinfo->is_pushed_down)
+       if (IS_OUTER_JOIN(jointype) &&
+           !RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids))
        {
            if (!is_remote_clause)
                return false;

diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index b35acb7bdcf17d2ba3baa728827f55f1449a8905..0cb9a88790f564646e47dcbd0f67988cbf5f59bb 100644 (file)
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -148,6 +148,7 @@ static bool has_indexed_join_quals(NestPath *joinpath);
 static double approx_tuple_count(PlannerInfo *root, JoinPath *path,
                   List *quals);
 static double calc_joinrel_size_estimate(PlannerInfo *root,
+                          RelOptInfo *joinrel,
                           RelOptInfo *outer_rel,
                           RelOptInfo *inner_rel,
                           double outer_rows,
@@ -3776,12 +3777,14 @@ compute_semi_anti_join_factors(PlannerInfo *root,
     */
    if (IS_OUTER_JOIN(jointype))
    {
+       Relids      joinrelids = bms_union(outerrel->relids, innerrel->relids);
+
        joinquals = NIL;
        foreach(l, restrictlist)
        {
            RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
 
-           if (!rinfo->is_pushed_down)
+           if (!RINFO_IS_PUSHED_DOWN(rinfo, joinrelids))
                joinquals = lappend(joinquals, rinfo);
        }
    }
@@ -4096,6 +4099,7 @@ set_joinrel_size_estimates(PlannerInfo *root, RelOptInfo *rel,
                           List *restrictlist)
 {
    rel->rows = calc_joinrel_size_estimate(root,
+                                          rel,
                                           outer_rel,
                                           inner_rel,
                                           outer_rel->rows,
@@ -4138,6 +4142,7 @@ get_parameterized_joinrel_size(PlannerInfo *root, RelOptInfo *rel,
     * estimate for any pair with the same parameterization.
     */
    nrows = calc_joinrel_size_estimate(root,
+                                      rel,
                                       outer_path->parent,
                                       inner_path->parent,
                                       outer_path->rows,
@@ -4161,6 +4166,7 @@ get_parameterized_joinrel_size(PlannerInfo *root, RelOptInfo *rel,
  */
 static double
 calc_joinrel_size_estimate(PlannerInfo *root,
+                          RelOptInfo *joinrel,
                           RelOptInfo *outer_rel,
                           RelOptInfo *inner_rel,
                           double outer_rows,
@@ -4213,7 +4219,7 @@ calc_joinrel_size_estimate(PlannerInfo *root,
        {
            RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
 
-           if (rinfo->is_pushed_down)
+           if (RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids))
                pushedquals = lappend(pushedquals, rinfo);
            else
                joinquals = lappend(joinquals, rinfo);

diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index bb1b3cf0a81b783e721466602f3b1a2ebe429169..2fb94ccdc514faf14d0fdd83638f908f893281bc 100644 (file)
--- a/src/backend/optimizer/path/joinpath.c
+++ b/src/backend/optimizer/path/joinpath.c
@@ -1606,7 +1606,7 @@ hash_inner_and_outer(PlannerInfo *root,
         * If processing an outer join, only use its own join clauses for
         * hashing.  For inner joins we need not be so picky.
         */
-       if (isouterjoin && restrictinfo->is_pushed_down)
+       if (isouterjoin && RINFO_IS_PUSHED_DOWN(restrictinfo, joinrel->relids))
            continue;
 
        if (!restrictinfo->can_join ||
@@ -1832,7 +1832,7 @@ select_mergejoin_clauses(PlannerInfo *root,
         * we don't set have_nonmergeable_joinclause here because pushed-down
         * clauses will become otherquals not joinquals.)
         */
-       if (isouterjoin && restrictinfo->is_pushed_down)
+       if (isouterjoin && RINFO_IS_PUSHED_DOWN(restrictinfo, joinrel->relids))
            continue;
 
        /* Check that clause is a mergeable operator clause */

diff --git a/src/backend/optimizer/path/joinrels.c b/src/backend/optimizer/path/joinrels.c
index 6ee23509c58d787fe0653762a31260829c90f321..4bbad04c055403cf04a62999ae05422a1714870a 100644 (file)
--- a/src/backend/optimizer/path/joinrels.c
+++ b/src/backend/optimizer/path/joinrels.c
@@ -31,6 +31,7 @@ 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,
+                             RelOptInfo *joinrel,
                              bool only_pushed_down);
 static void populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
                            RelOptInfo *rel2, RelOptInfo *joinrel,
@@ -770,7 +771,7 @@ populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
    {
        case JOIN_INNER:
            if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
-               restriction_is_constant_false(restrictlist, false))
+               restriction_is_constant_false(restrictlist, joinrel, false))
            {
                mark_dummy_rel(joinrel);
                break;
@@ -784,12 +785,12 @@ populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
            break;
        case JOIN_LEFT:
            if (is_dummy_rel(rel1) ||
-               restriction_is_constant_false(restrictlist, true))
+               restriction_is_constant_false(restrictlist, joinrel, true))
            {
                mark_dummy_rel(joinrel);
                break;
            }
-           if (restriction_is_constant_false(restrictlist, false) &&
+           if (restriction_is_constant_false(restrictlist, joinrel, false) &&
                bms_is_subset(rel2->relids, sjinfo->syn_righthand))
                mark_dummy_rel(rel2);
            add_paths_to_joinrel(root, joinrel, rel1, rel2,
@@ -801,7 +802,7 @@ populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
            break;
        case JOIN_FULL:
            if ((is_dummy_rel(rel1) && is_dummy_rel(rel2)) ||
-               restriction_is_constant_false(restrictlist, true))
+               restriction_is_constant_false(restrictlist, joinrel, true))
            {
                mark_dummy_rel(joinrel);
                break;
@@ -837,7 +838,7 @@ populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
                bms_is_subset(sjinfo->min_righthand, rel2->relids))
            {
                if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
-                   restriction_is_constant_false(restrictlist, false))
+                   restriction_is_constant_false(restrictlist, joinrel, false))
                {
                    mark_dummy_rel(joinrel);
                    break;
@@ -860,7 +861,7 @@ populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
                                   sjinfo) != NULL)
            {
                if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
-                   restriction_is_constant_false(restrictlist, false))
+                   restriction_is_constant_false(restrictlist, joinrel, false))
                {
                    mark_dummy_rel(joinrel);
                    break;
@@ -875,12 +876,12 @@ populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
            break;
        case JOIN_ANTI:
            if (is_dummy_rel(rel1) ||
-               restriction_is_constant_false(restrictlist, true))
+               restriction_is_constant_false(restrictlist, joinrel, true))
            {
                mark_dummy_rel(joinrel);
                break;
            }
-           if (restriction_is_constant_false(restrictlist, false) &&
+           if (restriction_is_constant_false(restrictlist, joinrel, false) &&
                bms_is_subset(rel2->relids, sjinfo->syn_righthand))
                mark_dummy_rel(rel2);
            add_paths_to_joinrel(root, joinrel, rel1, rel2,
@@ -1227,18 +1228,21 @@ mark_dummy_rel(RelOptInfo *rel)
 
 
 /*
- * restriction_is_constant_false --- is a restrictlist just FALSE?
+ * restriction_is_constant_false --- is a restrictlist just false?
  *
- * In cases where a qual is provably constant FALSE, eval_const_expressions
+ * In cases where a qual is provably constant false, eval_const_expressions
  * will generally have thrown away anything that's ANDed with it.  In outer
  * 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.
+ * If only_pushed_down is true, then consider only quals that are pushed-down
+ * from the point of view of the joinrel.
  */
 static bool
-restriction_is_constant_false(List *restrictlist, bool only_pushed_down)
+restriction_is_constant_false(List *restrictlist,
+                             RelOptInfo *joinrel,
+                             bool only_pushed_down)
 {
    ListCell   *lc;
 
@@ -1252,7 +1256,7 @@ restriction_is_constant_false(List *restrictlist, bool only_pushed_down)
    {
        RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
 
-       if (only_pushed_down && !rinfo->is_pushed_down)
+       if (only_pushed_down && !RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids))
            continue;
 
        if (rinfo->clause && IsA(rinfo->clause, Const))

diff --git a/src/backend/optimizer/plan/analyzejoins.c b/src/backend/optimizer/plan/analyzejoins.c
index 7dfce5bb55e5f760da58b86ff5a10bb4c2c00ad9..30bfde45ce6d9bf2cf49837cc4f5b38a28ccc803 100644 (file)
--- a/src/backend/optimizer/plan/analyzejoins.c
+++ b/src/backend/optimizer/plan/analyzejoins.c
@@ -253,8 +253,7 @@ join_is_removable(PlannerInfo *root, SpecialJoinInfo *sjinfo)
         * above the outer join, even if it references no other rels (it might
         * be from WHERE, for example).
         */
-       if (restrictinfo->is_pushed_down ||
-           !bms_equal(restrictinfo->required_relids, joinrelids))
+       if (RINFO_IS_PUSHED_DOWN(restrictinfo, joinrelids))
        {
            /*
             * If such a clause actually references the inner rel then join
@@ -422,8 +421,7 @@ remove_rel_from_query(PlannerInfo *root, int relid, Relids joinrelids)
 
        remove_join_clause_from_rels(root, rinfo, rinfo->required_relids);
 
-       if (rinfo->is_pushed_down ||
-           !bms_equal(rinfo->required_relids, joinrelids))
+       if (RINFO_IS_PUSHED_DOWN(rinfo, joinrelids))
        {
            /* Recheck that qual doesn't actually reference the target rel */
            Assert(!bms_is_member(relid, rinfo->clause_relids));
@@ -1080,6 +1078,7 @@ is_innerrel_unique_for(PlannerInfo *root,
                       JoinType jointype,
                       List *restrictlist)
 {
+   Relids      joinrelids = bms_union(outerrelids, innerrel->relids);
    List       *clause_list = NIL;
    ListCell   *lc;
 
@@ -1098,7 +1097,8 @@ is_innerrel_unique_for(PlannerInfo *root,
         * As noted above, if it's a pushed-down clause and we're at an outer
         * join, we can't use it.
         */
-       if (restrictinfo->is_pushed_down && IS_OUTER_JOIN(jointype))
+       if (IS_OUTER_JOIN(jointype) &&
+           RINFO_IS_PUSHED_DOWN(restrictinfo, joinrelids))
            continue;
 
        /* Ignore if it's not a mergejoinable clause */

diff --git a/src/backend/optimizer/plan/initsplan.c b/src/backend/optimizer/plan/initsplan.c
index 987c20ac9ff7a62d8716c72d07188b0d85211e06..4d0cc2a1c61057f26bf9aa6ffe665c7ebe0887ab 100644 (file)
--- a/src/backend/optimizer/plan/initsplan.c
+++ b/src/backend/optimizer/plan/initsplan.c
@@ -1754,6 +1754,11 @@ distribute_qual_to_rels(PlannerInfo *root, Node *clause,
     * attach quals to the lowest level where they can be evaluated.  But
     * if we were ever to re-introduce a mechanism for delaying evaluation
     * of "expensive" quals, this area would need work.
+    *
+    * Note: generally, use of is_pushed_down has to go through the macro
+    * RINFO_IS_PUSHED_DOWN, because that flag alone is not always sufficient
+    * to tell whether a clause must be treated as pushed-down in context.
+    * This seems like another reason why it should perhaps be rethought.
     *----------
     */
    if (is_deduced)

diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c
index fd66c1303db4fc33f95f603856f296da967ade5f..d5652b0f7285f908c034a6626369a0795bbb3f1a 100644 (file)
--- a/src/backend/optimizer/util/restrictinfo.c
+++ b/src/backend/optimizer/util/restrictinfo.c
@@ -371,7 +371,7 @@ extract_actual_clauses(List *restrictinfo_list,
  * extract_actual_join_clauses
  *
  * Extract bare clauses from 'restrictinfo_list', separating those that
- * syntactically match the join level from those that were pushed down.
+ * semantically match the join level from those that were pushed down.
  * Pseudoconstant clauses are excluded from the results.
  *
  * This is only used at outer joins, since for plain joins we don't care
@@ -392,15 +392,7 @@ extract_actual_join_clauses(List *restrictinfo_list,
    {
        RestrictInfo *rinfo = lfirst_node(RestrictInfo, l);
 
-       /*
-        * We must check both is_pushed_down and required_relids, since an
-        * outer-join clause that's been pushed down to some lower join level
-        * via path parameterization will not be marked is_pushed_down;
-        * nonetheless, it must be treated as a filter clause not a join
-        * clause so far as the lower join level is concerned.
-        */
-       if (rinfo->is_pushed_down ||
-           !bms_is_subset(rinfo->required_relids, joinrelids))
+       if (RINFO_IS_PUSHED_DOWN(rinfo, joinrelids))
        {
            if (!rinfo->pseudoconstant)
                *otherquals = lappend(*otherquals, rinfo->clause);

diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index 1e1c69155ba83a064140ae49ba20109456398150..9f789e78c166fbe88bb8f420be6bdf961b0255a6 100644 (file)
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -1669,7 +1669,8 @@ typedef struct LimitPath
  * if we decide that it can be pushed down into the nullable side of the join.
  * In that case it acts as a plain filter qual for wherever it gets evaluated.
  * (In short, is_pushed_down is only false for non-degenerate outer join
- * conditions.  Possibly we should rename it to reflect that meaning?)
+ * conditions.  Possibly we should rename it to reflect that meaning?  But
+ * see also the comments for RINFO_IS_PUSHED_DOWN, below.)
  *
  * RestrictInfo nodes also contain an outerjoin_delayed flag, which is true
  * if the clause's applicability must be delayed due to any outer joins
@@ -1809,6 +1810,20 @@ typedef struct RestrictInfo
    Selectivity right_bucketsize;   /* avg bucketsize of right side */
 } RestrictInfo;
 
+/*
+ * This macro embodies the correct way to test whether a RestrictInfo is
+ * "pushed down" to a given outer join, that is, should be treated as a filter
+ * clause rather than a join clause at that outer join.  This is certainly so
+ * if is_pushed_down is true; but examining that is not sufficient anymore,
+ * because outer-join clauses will get pushed down to lower outer joins when
+ * we generate a path for the lower outer join that is parameterized by the
+ * LHS of the upper one.  We can detect such a clause by noting that its
+ * required_relids exceed the scope of the join.
+ */
+#define RINFO_IS_PUSHED_DOWN(rinfo, joinrelids) \
+   ((rinfo)->is_pushed_down || \
+    !bms_is_subset((rinfo)->required_relids, joinrelids))
+
 /*
  * Since mergejoinscansel() is a relatively expensive function, and would
  * otherwise be invoked many times while planning a large join tree,