Fix inconsistent RestrictInfo serial numbers

When we generate multiple clones of the same qual condition to cope
with outer join identity 3, we need to ensure that all the clones get
the same serial number.  To achieve this, we reset the
root->last_rinfo_serial counter each time we produce RestrictInfo(s)
from the qual list (see deconstruct_distribute_oj_quals).  This
approach works only if we ensure that we are not changing the qual
list in any way that'd affect the number of RestrictInfos built from
it.

However, with b262ad440, an IS NULL qual on a NOT NULL column might
result in an additional constant-FALSE RestrictInfo.  And different
versions of the same qual clause can lead to different conclusions
about whether it can be reduced to constant-FALSE.  This would affect
the number of RestrictInfos built from the qual list for different
versions, causing inconsistent RestrictInfo serial numbers across
multiple clones of the same qual.  This inconsistency can confuse
users of these serial numbers, such as rebuild_joinclause_attr_needed,
and lead to planner errors such as "ERROR:  variable not found in
subplan target lists".

To fix, reset the root->last_rinfo_serial counter after generating the
additional constant-FALSE RestrictInfo.

Back-patch to v17 where the issue crept in.  In v17, I failed to make
a test case that would expose this bug, so no test case for v17.

Author: Richard Guo
Discussion: https://postgr.es/m/CAMbWs4-B6kafn+LmPuh-TYFwFyEm-vVj3Qqv7Yo-69CEv14rRg@mail.gmail.com

diff --git a/src/backend/optimizer/plan/initsplan.c b/src/backend/optimizer/plan/initsplan.c
index e2c68fe6f995e74d15c6a059c4767a72ebeba702..cd0ce25bd8694ecd7fe2375b50225d0cb2ab31a6 100644 (file)
--- a/src/backend/optimizer/plan/initsplan.c
+++ b/src/backend/optimizer/plan/initsplan.c
@@ -2657,11 +2657,18 @@ add_base_clause_to_rel(PlannerInfo *root, Index relid,
 
                /*
                 * Substitute the origin qual with constant-FALSE if it is provably
-                * always false.  Note that we keep the same rinfo_serial.
+                * always false.
+                *
+                * Note that we need to keep the same rinfo_serial, since it is in
+                * practice the same condition.  We also need to reset the
+                * last_rinfo_serial counter, which is essential to ensure that the
+                * RestrictInfos for the "same" qual condition get identical serial
+                * numbers (see deconstruct_distribute_oj_quals).
                 */
                if (restriction_is_always_false(root, restrictinfo))
                {
                        int                     save_rinfo_serial = restrictinfo->rinfo_serial;
+                       int                     save_last_rinfo_serial = root->last_rinfo_serial;
 
                        restrictinfo = make_restrictinfo(root,
                                                                                         (Expr *) makeBoolConst(false, false),
@@ -2674,6 +2681,7 @@ add_base_clause_to_rel(PlannerInfo *root, Index relid,
                                                                                         restrictinfo->incompatible_relids,
                                                                                         restrictinfo->outer_relids);
                        restrictinfo->rinfo_serial = save_rinfo_serial;
+                       root->last_rinfo_serial = save_last_rinfo_serial;
                }
        }
 

diff --git a/src/backend/optimizer/util/joininfo.c b/src/backend/optimizer/util/joininfo.c
index 5fb0c17630a196ac4cad7deda9dde253f7f670b8..65993bd6599d3fe3c4e25f13671667e8bf8f7d07 100644 (file)
--- a/src/backend/optimizer/util/joininfo.c
+++ b/src/backend/optimizer/util/joininfo.c
@@ -106,12 +106,19 @@ add_join_clause_to_rels(PlannerInfo *root,
                return;
 
        /*
-        * Substitute constant-FALSE for the origin qual if it is always false.
-        * Note that we keep the same rinfo_serial.
+        * Substitute the origin qual with constant-FALSE if it is provably always
+        * false.
+        *
+        * Note that we need to keep the same rinfo_serial, since it is in
+        * practice the same condition.  We also need to reset the
+        * last_rinfo_serial counter, which is essential to ensure that the
+        * RestrictInfos for the "same" qual condition get identical serial
+        * numbers (see deconstruct_distribute_oj_quals).
         */
        if (restriction_is_always_false(root, restrictinfo))
        {
                int                     save_rinfo_serial = restrictinfo->rinfo_serial;
+               int                     save_last_rinfo_serial = root->last_rinfo_serial;
 
                restrictinfo = make_restrictinfo(root,
                                                                                 (Expr *) makeBoolConst(false, false),
@@ -124,6 +131,7 @@ add_join_clause_to_rels(PlannerInfo *root,
                                                                                 restrictinfo->incompatible_relids,
                                                                                 restrictinfo->outer_relids);
                restrictinfo->rinfo_serial = save_rinfo_serial;
+               root->last_rinfo_serial = save_last_rinfo_serial;
        }
 
        cur_relid = -1;