Fix cache reference leak in contrib/sepgsql.

fixup_whole_row_references() did the wrong thing with a dropped column,
resulting in a commit-time warning about a cache reference leak.

I (tgl) added a test case exercising this, but back-patched the test
only as far as v10; the patch didn't apply cleanly to 9.6 and it
didn't seem worth the trouble to adapt it.  The bug is pretty old
though, so apply the code change all the way back.

Michael Luo, with cosmetic improvements by me

Discussion: https://postgr.es/m/BYAPR08MB5606D1453D7F50E2AF4D2FD29AD80@BYAPR08MB5606.namprd08.prod.outlook.com

1 files changed, 10 insertions, 11 deletions

diff --git a/contrib/sepgsql/dml.c b/contrib/sepgsql/dml.c
index d1e9f53cda9..745d2616dce 100644
--- a/contrib/sepgsql/dml.c
+++ b/contrib/sepgsql/dml.c
@@ -31,9 +31,9 @@
 /*
  * fixup_whole_row_references
  *
- * When user reference a whole of row, it is equivalent to reference to
+ * When user references a whole-row Var, it is equivalent to referencing
  * all the user columns (not system columns). So, we need to fix up the
- * given bitmapset, if it contains a whole of the row reference.
+ * given bitmapset, if it contains a whole-row reference.
  */
 static Bitmapset *
 fixup_whole_row_references(Oid relOid, Bitmapset *columns)
@@ -44,7 +44,7 @@ fixup_whole_row_references(Oid relOid, Bitmapset *columns)
 	AttrNumber	attno;
 	int			index;
 
-	/* if no whole of row references, do not anything */
+	/* if no whole-row references, nothing to do */
 	index = InvalidAttrNumber - FirstLowInvalidHeapAttributeNumber;
 	if (!bms_is_member(index, columns))
 		return columns;
@@ -56,7 +56,7 @@ fixup_whole_row_references(Oid relOid, Bitmapset *columns)
 	natts = ((Form_pg_class) GETSTRUCT(tuple))->relnatts;
 	ReleaseSysCache(tuple);
 
-	/* fix up the given columns */
+	/* remove bit 0 from column set, add in all the non-dropped columns */
 	result = bms_copy(columns);
 	result = bms_del_member(result, index);
 
@@ -66,14 +66,13 @@ fixup_whole_row_references(Oid relOid, Bitmapset *columns)
 								ObjectIdGetDatum(relOid),
 								Int16GetDatum(attno));
 		if (!HeapTupleIsValid(tuple))
-			continue;
-
-		if (((Form_pg_attribute) GETSTRUCT(tuple))->attisdropped)
-			continue;
-
-		index = attno - FirstLowInvalidHeapAttributeNumber;
+			continue;			/* unexpected case, should we error? */
 
-		result = bms_add_member(result, index);
+		if (!((Form_pg_attribute) GETSTRUCT(tuple))->attisdropped)
+		{
+			index = attno - FirstLowInvalidHeapAttributeNumber;
+			result = bms_add_member(result, index);
+		}
 
 		ReleaseSysCache(tuple);
 	}