Fix oversight in 8.0 modification of RestrictInfo data structures.

A RestrictInfo representing an OR clause now contains two versions of
the contained expression, one with sub-RestrictInfos and one without.
clause_selectivity() should descend to the version with sub-RestrictInfos
so that it has a chance of caching its results for the OR's sub-clauses.
Failing to do so resulted in redundant planner effort.

diff --git a/src/backend/optimizer/path/clausesel.c b/src/backend/optimizer/path/clausesel.c
index 7d96886ccc6e25aa95b0270f1195346bff5bebf7..4d48d41a69e75ed0ccf0594503be4abddda59a62 100644 (file)
--- a/src/backend/optimizer/path/clausesel.c
+++ b/src/backend/optimizer/path/clausesel.c
@@ -461,8 +461,15 @@ clause_selectivity(Query *root,
                        }
                }
 
-               /* Proceed with examination of contained clause */
-               clause = (Node *) rinfo->clause;
+               /*
+                * Proceed with examination of contained clause.  If the clause is an
+                * OR-clause, we want to look at the variant with sub-RestrictInfos,
+                * so that per-subclause selectivities can be cached.
+                */
+               if (rinfo->orclause)
+                       clause = (Node *) rinfo->orclause;
+               else
+                       clause = (Node *) rinfo->clause;
        }
 
        if (IsA(clause, Var))