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

1 files changed, 2 insertions, 4 deletions

diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 1ee3b93b1e3..7aab644e456 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -1875,9 +1875,8 @@ get_loop_count(PlannerInfo *root, Relids outer_relids)
 	{
 		int			relid;
 
-		/* Need a working copy since bms_first_member is destructive */
-		outer_relids = bms_copy(outer_relids);
-		while ((relid = bms_first_member(outer_relids)) >= 0)
+		relid = -1;
+		while ((relid = bms_next_member(outer_relids, relid)) >= 0)
 		{
 			RelOptInfo *outer_rel;
 
@@ -1900,7 +1899,6 @@ get_loop_count(PlannerInfo *root, Relids outer_relids)
 			if (result == 1.0 || result > outer_rel->rows)
 				result = outer_rel->rows;
 		}
-		bms_free(outer_relids);
 	}
 	return result;
 }