Add bms_next_member(), and use it where appropriate.

This patch adds a way of iterating through the members of a bitmapset
nondestructively, unlike the old way with bms_first_member().  While
bms_next_member() is very slightly slower than bms_first_member()
(at least for typical-size bitmapsets), eliminating the need to palloc
and pfree a temporary copy of the target bitmapset is a significant win.
So this method should be preferred in all cases where a temporary copy
would be necessary.

Tom Lane, with suggestions from Dean Rasheed and David Rowley

2 files changed, 5 insertions, 9 deletions

diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index ad983c7158..2ed64279f0 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -2456,11 +2456,10 @@ static Bitmapset *
 adjust_view_column_set(Bitmapset *cols, List *targetlist)
 {
 	Bitmapset  *result = NULL;
-	Bitmapset  *tmpcols;
-	AttrNumber	col;
+	int			col;
 
-	tmpcols = bms_copy(cols);
-	while ((col = bms_first_member(tmpcols)) >= 0)
+	col = -1;
+	while ((col = bms_next_member(cols, col)) >= 0)
 	{
 		/* bit numbers are offset by FirstLowInvalidHeapAttributeNumber */
 		AttrNumber	attno = col + FirstLowInvalidHeapAttributeNumber;
@@ -2510,7 +2509,6 @@ adjust_view_column_set(Bitmapset *cols, List *targetlist)
 					 attno);
 		}
 	}
-	bms_free(tmpcols);
 
 	return result;
 }
diff --git a/src/backend/rewrite/rewriteManip.c b/src/backend/rewrite/rewriteManip.c
index fb203146b1..c9e4b68341 100644
--- a/src/backend/rewrite/rewriteManip.c
+++ b/src/backend/rewrite/rewriteManip.c
@@ -454,13 +454,11 @@ static Relids
 offset_relid_set(Relids relids, int offset)
 {
 	Relids		result = NULL;
-	Relids		tmprelids;
 	int			rtindex;
 
-	tmprelids = bms_copy(relids);
-	while ((rtindex = bms_first_member(tmprelids)) >= 0)
+	rtindex = -1;
+	while ((rtindex = bms_next_member(relids, rtindex)) >= 0)
 		result = bms_add_member(result, rtindex + offset);
-	bms_free(tmprelids);
 	return result;
 }