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, 8 insertions, 6 deletions

diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c
index 76bda739357..c3039a6480e 100644
--- a/contrib/postgres_fdw/postgres_fdw.c
+++ b/contrib/postgres_fdw/postgres_fdw.c
@@ -1198,15 +1198,17 @@ postgresPlanForeignModify(PlannerInfo *root,
 	}
 	else if (operation == CMD_UPDATE)
 	{
-		Bitmapset  *tmpset = bms_copy(rte->modifiedCols);
-		AttrNumber	col;
+		int			col;
 
-		while ((col = bms_first_member(tmpset)) >= 0)
+		col = -1;
+		while ((col = bms_next_member(rte->modifiedCols, col)) >= 0)
 		{
-			col += FirstLowInvalidHeapAttributeNumber;
-			if (col <= InvalidAttrNumber)		/* shouldn't happen */
+			/* bit numbers are offset by FirstLowInvalidHeapAttributeNumber */
+			AttrNumber	attno = col + FirstLowInvalidHeapAttributeNumber;
+
+			if (attno <= InvalidAttrNumber)		/* shouldn't happen */
 				elog(ERROR, "system-column update is not supported");
-			targetAttrs = lappend_int(targetAttrs, col);
+			targetAttrs = lappend_int(targetAttrs, attno);
 		}
 	}