Improve usage of effective_cache_size parameter by assuming that all the

tables in the query compete for cache space, not just the one we are
currently costing an indexscan for.  This seems more realistic, and it
definitely will help in examples recently exhibited by Stefan
Kaltenbrunner.  To get the total size of all the tables involved, we must
tweak the handling of 'append relations' a bit --- formerly we looked up
information about the child tables on-the-fly during set_append_rel_pathlist,
but it needs to be done before we start doing any cost estimation, so
push it into the add_base_rels_to_query scan.

1 files changed, 18 insertions, 6 deletions

diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index 5e3c7d98575..aba4b881571 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.125 2006/08/25 04:06:50 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/plancat.c,v 1.126 2006/09/19 22:49:53 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -62,9 +62,15 @@ static List *get_relation_constraints(Oid relationObjectId, RelOptInfo *rel);
  * Also, initialize the attr_needed[] and attr_widths[] arrays.  In most
  * cases these are left as zeroes, but sometimes we need to compute attr
  * widths here, and we may as well cache the results for costsize.c.
+ *
+ * If inhparent is true, all we need to do is set up the attr arrays:
+ * the RelOptInfo actually represents the appendrel formed by an inheritance
+ * tree, and so the parent rel's physical size and index information isn't
+ * important for it.
  */
 void
-get_relation_info(PlannerInfo *root, Oid relationObjectId, RelOptInfo *rel)
+get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
+				  RelOptInfo *rel)
 {
 	Index		varno = rel->relid;
 	Relation	relation;
@@ -88,15 +94,21 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, RelOptInfo *rel)
 		palloc0((rel->max_attr - rel->min_attr + 1) * sizeof(int32));
 
 	/*
-	 * Estimate relation size.
+	 * Estimate relation size --- unless it's an inheritance parent, in which
+	 * case the size will be computed later in set_append_rel_pathlist, and
+	 * we must leave it zero for now to avoid bollixing the total_table_pages
+	 * calculation.
 	 */
-	estimate_rel_size(relation, rel->attr_widths - rel->min_attr,
-					  &rel->pages, &rel->tuples);
+	if (!inhparent)
+		estimate_rel_size(relation, rel->attr_widths - rel->min_attr,
+						  &rel->pages, &rel->tuples);
 
 	/*
 	 * Make list of indexes.  Ignore indexes on system catalogs if told to.
+	 * Don't bother with indexes for an inheritance parent, either.
 	 */
-	if (IgnoreSystemIndexes && IsSystemClass(relation->rd_rel))
+	if (inhparent ||
+		(IgnoreSystemIndexes && IsSystemClass(relation->rd_rel)))
 		hasindex = false;
 	else
 		hasindex = relation->rd_rel->relhasindex;