From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 5 Oct 2005 17:19:19 +0000 (+0000)
Subject: Make set_function_size_estimates() marginally smarter: per original
X-Git-Url: http://waps.l3s.uni-hannover.de/gitweb/?a=commitdiff_plain;h=42e6ace12c11242c7d9e990d7a3efa33363451d5;p=users%2Fbernd%2Fpostgres.git

Make set_function_size_estimates() marginally smarter: per original
comment, it can at least test whether the expression returns set.
---

diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index 75b6928209..77af01491b 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -1898,17 +1898,23 @@ join_in_selectivity(JoinPath *path, PlannerInfo *root)
 void
 set_function_size_estimates(PlannerInfo *root, RelOptInfo *rel)
 {
+	RangeTblEntry *rte;
+
 	/* Should only be applied to base relations that are functions */
 	Assert(rel->relid > 0);
-	Assert(rel->rtekind == RTE_FUNCTION);
+	rte = rt_fetch(rel->relid, root->parse->rtable);
+	Assert(rte->rtekind == RTE_FUNCTION);
 
 	/*
 	 * Estimate number of rows the function itself will return.
 	 *
-	 * XXX no idea how to do this yet; but should at least check whether
+	 * XXX no idea how to do this yet; but we can at least check whether
 	 * function returns set or not...
 	 */
-	rel->tuples = 1000;
+	if (expression_returns_set(rte->funcexpr))
+		rel->tuples = 1000;
+	else
+		rel->tuples = 1;
 
 	/* Now estimate number of output rows, etc */
 	set_baserel_size_estimates(root, rel);