Restructure building of join relation targetlists so that a join plan

node emits only those vars that are actually needed above it in the
plan tree.  (There were comments in the code suggesting that this was
done at some point in the dim past, but for a long time we have just
made join nodes emit everything that either input emitted.)  Aside from
being marginally more efficient, this fixes the problem noted by Peter
Eisentraut where a join above an IN-implemented-as-join might fail,
because the subplan targetlist constructed in the latter case didn't
meet the expectation of including everything.
Along the way, fix some places that were O(N^2) in the targetlist
length.  This is not all the trouble spots for wide queries by any
means, but it's a step forward.

1 files changed, 31 insertions, 1 deletions

diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index 5798b726497..45c6ead0fc0 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -14,7 +14,7 @@
  * Copyright (c) 2003, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/nodes/bitmapset.c,v 1.1 2003/02/08 20:20:53 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/nodes/bitmapset.c,v 1.2 2003/06/29 23:05:04 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -389,6 +389,36 @@ bms_overlap(const Bitmapset *a, const Bitmapset *b)
 }
 
 /*
+ * bms_nonempty_difference - do sets have a nonempty difference?
+ */
+bool
+bms_nonempty_difference(const Bitmapset *a, const Bitmapset *b)
+{
+	int			shortlen;
+	int			i;
+
+	/* Handle cases where either input is NULL */
+	if (a == NULL)
+		return false;
+	if (b == NULL)
+		return !bms_is_empty(a);
+	/* Check words in common */
+	shortlen = Min(a->nwords, b->nwords);
+	for (i = 0; i < shortlen; i++)
+	{
+		if ((a->words[i] & ~ b->words[i]) != 0)
+			return true;
+	}
+	/* Check extra words in a */
+	for (; i < a->nwords; i++)
+	{
+		if (a->words[i] != 0)
+			return true;
+	}
+	return false;
+}
+
+/*
  * bms_singleton_member - return the sole integer member of set
  *
  * Raises error if |a| is not 1.