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, 14 insertions, 15 deletions

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index c499486f016..8c799d3c21b 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -547,7 +547,6 @@ ExecCheckRTEPerms(RangeTblEntry *rte)
 	AclMode		remainingPerms;
 	Oid			relOid;
 	Oid			userid;
-	Bitmapset  *tmpset;
 	int			col;
 
 	/*
@@ -614,12 +613,13 @@ ExecCheckRTEPerms(RangeTblEntry *rte)
 					return false;
 			}
 
-			tmpset = bms_copy(rte->selectedCols);
-			while ((col = bms_first_member(tmpset)) >= 0)
+			col = -1;
+			while ((col = bms_next_member(rte->selectedCols, col)) >= 0)
 			{
-				/* remove the column number offset */
-				col += FirstLowInvalidHeapAttributeNumber;
-				if (col == InvalidAttrNumber)
+				/* bit #s are offset by FirstLowInvalidHeapAttributeNumber */
+				AttrNumber	attno = col + FirstLowInvalidHeapAttributeNumber;
+
+				if (attno == InvalidAttrNumber)
 				{
 					/* Whole-row reference, must have priv on all cols */
 					if (pg_attribute_aclcheck_all(relOid, userid, ACL_SELECT,
@@ -628,12 +628,11 @@ ExecCheckRTEPerms(RangeTblEntry *rte)
 				}
 				else
 				{
-					if (pg_attribute_aclcheck(relOid, col, userid,
+					if (pg_attribute_aclcheck(relOid, attno, userid,
 											  ACL_SELECT) != ACLCHECK_OK)
 						return false;
 				}
 			}
-			bms_free(tmpset);
 		}
 
 		/*
@@ -656,24 +655,24 @@ ExecCheckRTEPerms(RangeTblEntry *rte)
 					return false;
 			}
 
-			tmpset = bms_copy(rte->modifiedCols);
-			while ((col = bms_first_member(tmpset)) >= 0)
+			col = -1;
+			while ((col = bms_next_member(rte->modifiedCols, col)) >= 0)
 			{
-				/* remove the column number offset */
-				col += FirstLowInvalidHeapAttributeNumber;
-				if (col == InvalidAttrNumber)
+				/* bit #s are offset by FirstLowInvalidHeapAttributeNumber */
+				AttrNumber	attno = col + FirstLowInvalidHeapAttributeNumber;
+
+				if (attno == InvalidAttrNumber)
 				{
 					/* whole-row reference can't happen here */
 					elog(ERROR, "whole-row update is not implemented");
 				}
 				else
 				{
-					if (pg_attribute_aclcheck(relOid, col, userid,
+					if (pg_attribute_aclcheck(relOid, attno, userid,
 											  remainingPerms) != ACLCHECK_OK)
 						return false;
 				}
 			}
-			bms_free(tmpset);
 		}
 	}
 	return true;