Yet further fixes for multi-row VALUES lists for updatable views.

tglsfdc · tglsfdc · commit 23e2a06acf04 · 2022-10-11T18:24:15.000-04:00
DEFAULT markers appearing in an INSERT on an updatable view could be mis-processed if they were in a multi-row VALUES clause. This would lead to strange errors such as "cache lookup failed for type NNNN", or in older branches even to crashes. The cause is that commit 41531e4 tried to re-use rewriteValuesRTE() to remove any SetToDefault nodes (that hadn't previously been replaced by the view's own default values) appearing in "product" queries, that is DO ALSO queries. That's fundamentally wrong because the DO ALSO queries might not even be INSERTs; and even if they are, their targetlists don't necessarily match the view's column list, so that almost all the logic in rewriteValuesRTE() is inapplicable. What we want is a narrow focus on replacing any such nodes with NULL constants. (That is, in this context we are interpreting the defaults as being strictly those of the view itself; and we already replaced any that aren't NULL.) We could add still more !force_nulls tests to further lobotomize rewriteValuesRTE(); but it seems cleaner to split out this case to a new function, restoring rewriteValuesRTE() to the charter it had before. Per bug #17633 from jiye_sw. Patch by me, but thanks to Richard Guo and Japin Li for initial investigation. Back-patch to all supported branches, as the previous fix was. Discussion: https://postgr.es/m/17633-98cc85e1fa91e905@postgresql.org
diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
@@ -72,7 +72,8 @@ static TargetEntry *process_matched_tle(TargetEntry *src_tle,
 					const char *attrName);
 static Node *get_assignment_input(Node *node);
 static bool rewriteValuesRTE(Query *parsetree, RangeTblEntry *rte, int rti,
-				 Relation target_relation, bool force_nulls);
+							 Relation target_relation);
+static void rewriteValuesRTEToNulls(Query *parsetree, RangeTblEntry *rte);
 static void markQueryForLocking(Query *qry, Node *jtnode,
 					LockClauseStrength strength, LockWaitPolicy waitPolicy,
 					bool pushedDown);
@@ -1233,17 +1234,6 @@ searchForDefault(RangeTblEntry *rte)
  * all DEFAULT items are replaced, and if the target relation doesn't have a
  * default, the value is explicitly set to NULL.
  *
- * Additionally, if force_nulls is true, the target relation's defaults are
- * ignored and all DEFAULT items in the VALUES list are explicitly set to
- * NULL, regardless of the target relation's type.  This is used for the
- * product queries generated by DO ALSO rules attached to an auto-updatable
- * view, for which we will have already called this function with force_nulls
- * false.  For these product queries, we must then force any remaining DEFAULT
- * items to NULL to provide concrete values for the rule actions.
- * Essentially, this is a mix of the 2 cases above --- the original query is
- * an insert into an auto-updatable view, and the product queries are inserts
- * into a rule-updatable view.
- *
  * Note that we may have subscripted or field assignment targetlist entries,
  * as well as more complex expressions from already-replaced DEFAULT items if
  * we have recursed to here for an auto-updatable view. However, it ought to
@@ -1256,7 +1246,7 @@ searchForDefault(RangeTblEntry *rte)
  */
 static bool
 rewriteValuesRTE(Query *parsetree, RangeTblEntry *rte, int rti,
-				 Relation target_relation, bool force_nulls)
+				 Relation target_relation)
 {
 	List	   *newValues;
 	ListCell   *lc;
@@ -1265,15 +1255,16 @@ rewriteValuesRTE(Query *parsetree, RangeTblEntry *rte, int rti,
 	int			numattrs;
 	int		   *attrnos;
 
+	/* Steps below are not sensible for non-INSERT queries */
+	Assert(parsetree->commandType == CMD_INSERT);
+	Assert(rte->rtekind == RTE_VALUES);
+
 	/*
 	 * Rebuilding all the lists is a pretty expensive proposition in a big
 	 * VALUES list, and it's a waste of time if there aren't any DEFAULT
 	 * placeholders.  So first scan to see if there are any.
-	 *
-	 * We skip this check if force_nulls is true, because we know that there
-	 * are DEFAULT items present in that case.
 	 */
-	if (!force_nulls && !searchForDefault(rte))
+	if (!searchForDefault(rte))
 		return true;			/* nothing to do */
 
 	/*
@@ -1307,12 +1298,10 @@ rewriteValuesRTE(Query *parsetree, RangeTblEntry *rte, int rti,
 	/*
 	 * Check if the target relation is an auto-updatable view, in which case
 	 * unresolved defaults will be left untouched rather than being set to
-	 * NULL.  If force_nulls is true, we always set DEFAULT items to NULL, so
-	 * skip this check in that case --- it isn't an auto-updatable view.
+	 * NULL.
 	 */
 	isAutoUpdatableView = false;
-	if (!force_nulls &&
-		target_relation->rd_rel->relkind == RELKIND_VIEW &&
+	if (target_relation->rd_rel->relkind == RELKIND_VIEW &&
 		!view_has_instead_trigger(target_relation, CMD_INSERT))
 	{
 		List	   *locks;
@@ -1370,9 +1359,10 @@ rewriteValuesRTE(Query *parsetree, RangeTblEntry *rte, int rti,
 
 				if (attrno == 0)
 					elog(ERROR, "cannot set value in column %d to DEFAULT", i);
+				Assert(attrno > 0 && attrno <= target_relation->rd_att->natts);
 				att_tup = target_relation->rd_att->attrs[attrno - 1];
 
-				if (!force_nulls && !att_tup->attisdropped)
+				if (!att_tup->attisdropped)
 					new_expr = build_column_default(target_relation, attrno);
 				else
 					new_expr = NULL;	/* force a NULL if dropped */
@@ -1422,6 +1412,50 @@ rewriteValuesRTE(Query *parsetree, RangeTblEntry *rte, int rti,
 	return allReplaced;
 }
 
+/*
+ * Mop up any remaining DEFAULT items in the given VALUES RTE by
+ * replacing them with NULL constants.
+ *
+ * This is used for the product queries generated by DO ALSO rules attached to
+ * an auto-updatable view.  The action can't depend on the "target relation"
+ * since the product query might not have one (it needn't be an INSERT).
+ * Essentially, such queries are treated as being attached to a rule-updatable
+ * view.
+ */
+static void
+rewriteValuesRTEToNulls(Query *parsetree, RangeTblEntry *rte)
+{
+	List	   *newValues;
+	ListCell   *lc;
+
+	Assert(rte->rtekind == RTE_VALUES);
+	newValues = NIL;
+	foreach(lc, rte->values_lists)
+	{
+		List	   *sublist = (List *) lfirst(lc);
+		List	   *newList = NIL;
+		ListCell   *lc2;
+
+		foreach(lc2, sublist)
+		{
+			Node	   *col = (Node *) lfirst(lc2);
+
+			if (IsA(col, SetToDefault))
+			{
+				SetToDefault *def = (SetToDefault *) col;
+
+				newList = lappend(newList, makeNullConst(def->typeId,
+														 def->typeMod,
+														 def->collation));
+			}
+			else
+				newList = lappend(newList, col);
+		}
+		newValues = lappend(newValues, newList);
+	}
+	rte->values_lists = newValues;
+}
+
 
 /*
  * rewriteTargetListUD - rewrite UPDATE/DELETE targetlist as needed
@@ -3578,7 +3612,7 @@ RewriteQuery(Query *parsetree, List *rewrite_events)
 															parsetree->resultRelation);
 				/* ... and the VALUES expression lists */
 				if (!rewriteValuesRTE(parsetree, values_rte, values_rte_index,
-									  rt_entry_relation, false))
+									  rt_entry_relation))
 					defaults_remaining = true;
 			}
 			else
@@ -3655,9 +3689,7 @@ RewriteQuery(Query *parsetree, List *rewrite_events)
 				RangeTblEntry *values_rte = rt_fetch(values_rte_index,
 													 pt->rtable);
 
-				rewriteValuesRTE(pt, values_rte, values_rte_index,
-								 rt_entry_relation,
-								 true); /* Force remaining defaults to NULL */
+				rewriteValuesRTEToNulls(pt, values_rte);
 			}
 		}
 
diff --git a/src/test/regress/expected/updatable_views.out b/src/test/regress/expected/updatable_views.out
@@ -431,8 +431,30 @@ EXPLAIN (costs off) DELETE FROM rw_view1 WHERE a=5;
          Index Cond: ((a > 0) AND (a = 5))
 (3 rows)
 
+-- it's still updatable if we add a DO ALSO rule
+CREATE TABLE base_tbl_hist(ts timestamptz default now(), a int, b text);
+CREATE RULE base_tbl_log AS ON INSERT TO rw_view1 DO ALSO
+  INSERT INTO base_tbl_hist(a,b) VALUES(new.a, new.b);
+SELECT table_name, is_updatable, is_insertable_into
+  FROM information_schema.views
+ WHERE table_name = 'rw_view1';
+ table_name | is_updatable | is_insertable_into 
+------------+--------------+--------------------
+ rw_view1   | YES          | YES
+(1 row)
+
+-- Check behavior with DEFAULTs (bug #17633)
+INSERT INTO rw_view1 VALUES (9, DEFAULT), (10, DEFAULT);
+SELECT a, b FROM base_tbl_hist;
+ a  | b 
+----+---
+  9 | 
+ 10 | 
+(2 rows)
+
 DROP TABLE base_tbl CASCADE;
 NOTICE:  drop cascades to view rw_view1
+DROP TABLE base_tbl_hist;
 -- view on top of view
 CREATE TABLE base_tbl (a int PRIMARY KEY, b text DEFAULT 'Unspecified');
 INSERT INTO base_tbl SELECT i, 'Row ' || i FROM generate_series(-2, 2) g(i);
diff --git a/src/test/regress/sql/updatable_views.sql b/src/test/regress/sql/updatable_views.sql
@@ -145,7 +145,24 @@ SELECT * FROM base_tbl;
 EXPLAIN (costs off) UPDATE rw_view1 SET a=6 WHERE a=5;
 EXPLAIN (costs off) DELETE FROM rw_view1 WHERE a=5;
 
+-- it's still updatable if we add a DO ALSO rule
+
+CREATE TABLE base_tbl_hist(ts timestamptz default now(), a int, b text);
+
+CREATE RULE base_tbl_log AS ON INSERT TO rw_view1 DO ALSO
+  INSERT INTO base_tbl_hist(a,b) VALUES(new.a, new.b);
+
+SELECT table_name, is_updatable, is_insertable_into
+  FROM information_schema.views
+ WHERE table_name = 'rw_view1';
+
+-- Check behavior with DEFAULTs (bug #17633)
+
+INSERT INTO rw_view1 VALUES (9, DEFAULT), (10, DEFAULT);
+SELECT a, b FROM base_tbl_hist;
+
 DROP TABLE base_tbl CASCADE;
+DROP TABLE base_tbl_hist;
 
 -- view on top of view
 
