From af95d7aa63be1d03bad6070d090874d3dfa046e8 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu, 7 Aug 2008 19:35:02 +0000
Subject: Improve INTERSECT/EXCEPT hashing by realizing that we don't need to
 make any hashtable entries for tuples that are found only in the second
 input: they can never contribute to the output.  Furthermore, this implies
 that the planner should endeavor to put first the smaller (in number of
 groups) input relation for an INTERSECT.  Implement that, and upgrade
 prepunion's estimation of the number of rows returned by setops so that
 there's some amount of sanity in the estimate of which one is smaller.

---
 src/backend/optimizer/util/tlist.c | 104 +++++++++++++++++++++++--------------
 1 file changed, 64 insertions(+), 40 deletions(-)

(limited to 'src/backend/optimizer/util/tlist.c')

diff --git a/src/backend/optimizer/util/tlist.c b/src/backend/optimizer/util/tlist.c
index a2c627fd4d5..b2fb112ebef 100644
--- a/src/backend/optimizer/util/tlist.c
+++ b/src/backend/optimizer/util/tlist.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/optimizer/util/tlist.c,v 1.80 2008/08/07 01:11:50 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/optimizer/util/tlist.c,v 1.81 2008/08/07 19:35:02 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -133,6 +133,69 @@ add_to_flat_tlist(List *tlist, List *vars)
 }
 
 
+/*
+ * get_tlist_exprs
+ *		Get just the expression subtrees of a tlist
+ *
+ * Resjunk columns are ignored unless includeJunk is true
+ */
+List *
+get_tlist_exprs(List *tlist, bool includeJunk)
+{
+	List	   *result = NIL;
+	ListCell   *l;
+
+	foreach(l, tlist)
+	{
+		TargetEntry *tle = (TargetEntry *) lfirst(l);
+
+		if (tle->resjunk && !includeJunk)
+			continue;
+
+		result = lappend(result, tle->expr);
+	}
+	return result;
+}
+
+
+/*
+ * Does tlist have same output datatypes as listed in colTypes?
+ *
+ * Resjunk columns are ignored if junkOK is true; otherwise presence of
+ * a resjunk column will always cause a 'false' result.
+ *
+ * Note: currently no callers care about comparing typmods.
+ */
+bool
+tlist_same_datatypes(List *tlist, List *colTypes, bool junkOK)
+{
+	ListCell   *l;
+	ListCell   *curColType = list_head(colTypes);
+
+	foreach(l, tlist)
+	{
+		TargetEntry *tle = (TargetEntry *) lfirst(l);
+
+		if (tle->resjunk)
+		{
+			if (!junkOK)
+				return false;
+		}
+		else
+		{
+			if (curColType == NULL)
+				return false;	/* tlist longer than colTypes */
+			if (exprType((Node *) tle->expr) != lfirst_oid(curColType))
+				return false;
+			curColType = lnext(curColType);
+		}
+	}
+	if (curColType != NULL)
+		return false;			/* tlist shorter than colTypes */
+	return true;
+}
+
+
 /*
  * get_sortgroupref_tle
  *		Find the targetlist entry matching the given SortGroupRef index,
@@ -303,42 +366,3 @@ grouping_is_hashable(List *groupClause)
 	}
 	return true;
 }
-
-
-
-/*
- * Does tlist have same output datatypes as listed in colTypes?
- *
- * Resjunk columns are ignored if junkOK is true; otherwise presence of
- * a resjunk column will always cause a 'false' result.
- *
- * Note: currently no callers care about comparing typmods.
- */
-bool
-tlist_same_datatypes(List *tlist, List *colTypes, bool junkOK)
-{
-	ListCell   *l;
-	ListCell   *curColType = list_head(colTypes);
-
-	foreach(l, tlist)
-	{
-		TargetEntry *tle = (TargetEntry *) lfirst(l);
-
-		if (tle->resjunk)
-		{
-			if (!junkOK)
-				return false;
-		}
-		else
-		{
-			if (curColType == NULL)
-				return false;	/* tlist longer than colTypes */
-			if (exprType((Node *) tle->expr) != lfirst_oid(curColType))
-				return false;
-			curColType = lnext(curColType);
-		}
-	}
-	if (curColType != NULL)
-		return false;			/* tlist shorter than colTypes */
-	return true;
-}
-- 
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