From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 11 Oct 2005 16:45:00 +0000 (+0000)
Subject: Fix oversight in 8.0 modification of RestrictInfo data structures.
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=55a1160fd8f7831b08d9deb181bf378d4366fe5e;p=users%2Fbernd%2Fpostgres.git

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 7d96886ccc..4d48d41a69 100644
--- 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))