Fix multi-row DEFAULT handling for INSERT ... SELECT rules.

deanrasheed · deanrasheed · commit 75c737636b8a · 2023-02-23T10:53:01.000Z
Given an updatable view with a DO ALSO INSERT ... SELECT rule, a multi-row INSERT ... VALUES query on the view fails if the VALUES list contains any DEFAULTs that are not replaced by view defaults. This manifests as an "unrecognized node type" error, or an Assert failure, in an assert-enabled build. The reason is that when RewriteQuery() attempts to replace the remaining DEFAULT items with NULLs in any product queries, using rewriteValuesRTEToNulls(), it assumes that the VALUES RTE is located at the same rangetable index in each product query. However, if the product query is an INSERT ... SELECT, then the VALUES RTE is actually in the SELECT part of that query (at the same index), rather than the top-level product query itself. Fix, by descending to the SELECT in such cases. Note that we can't simply use getInsertSelectQuery() for this, since that expects to be given a raw rule action with OLD and NEW placeholder entries, so we duplicate its logic instead. While at it, beef up the checks in getInsertSelectQuery() by checking that the jointree->fromlist node is indeed a RangeTblRef, and that the RTE it points to has rtekind == RTE_SUBQUERY. Per bug #17803, from Alexander Lakhin. Back-patch to all supported branches. Dean Rasheed, reviewed by Tom Lane. Discussion: https://postgr.es/m/17803-53c63ed4ecb4eac6%40postgresql.org
diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
@@ -1604,7 +1604,6 @@ rewriteValuesRTEToNulls(Query *parsetree, RangeTblEntry *rte)
 	List	   *newValues;
 	ListCell   *lc;
 
-	Assert(rte->rtekind == RTE_VALUES);
 	newValues = NIL;
 	foreach(lc, rte->values_lists)
 	{
@@ -3861,12 +3860,39 @@ RewriteQuery(Query *parsetree, List *rewrite_events, int orig_rt_length)
 			/*
 			 * Each product query has its own copy of the VALUES RTE at the
 			 * same index in the rangetable, so we must finalize each one.
+			 *
+			 * Note that if the product query is an INSERT ... SELECT, then
+			 * the VALUES RTE will be at the same index in the SELECT part of
+			 * the product query rather than the top-level product query
+			 * itself.
 			 */
 			foreach(n, product_queries)
 			{
 				Query	   *pt = (Query *) lfirst(n);
-				RangeTblEntry *values_rte = rt_fetch(values_rte_index,
-													 pt->rtable);
+				RangeTblEntry *values_rte;
+
+				if (pt->commandType == CMD_INSERT &&
+					pt->jointree && IsA(pt->jointree, FromExpr) &&
+					list_length(pt->jointree->fromlist) == 1)
+				{
+					Node	   *jtnode = (Node *) linitial(pt->jointree->fromlist);
+
+					if (IsA(jtnode, RangeTblRef))
+					{
+						int			rtindex = ((RangeTblRef *) jtnode)->rtindex;
+						RangeTblEntry *src_rte = rt_fetch(rtindex, pt->rtable);
+
+						if (src_rte->rtekind == RTE_SUBQUERY &&
+							src_rte->subquery &&
+							IsA(src_rte->subquery, Query) &&
+							src_rte->subquery->commandType == CMD_SELECT)
+							pt = src_rte->subquery;
+					}
+				}
+
+				values_rte = rt_fetch(values_rte_index, pt->rtable);
+				if (values_rte->rtekind != RTE_VALUES)
+					elog(ERROR, "failed to find VALUES RTE in product query");
 
 				rewriteValuesRTEToNulls(pt, values_rte);
 			}
diff --git a/src/backend/rewrite/rewriteManip.c b/src/backend/rewrite/rewriteManip.c
@@ -1012,12 +1012,15 @@ getInsertSelectQuery(Query *parsetree, Query ***subquery_ptr)
 	if (list_length(parsetree->jointree->fromlist) != 1)
 		elog(ERROR, "expected to find SELECT subquery");
 	rtr = (RangeTblRef *) linitial(parsetree->jointree->fromlist);
-	Assert(IsA(rtr, RangeTblRef));
+	if (!IsA(rtr, RangeTblRef))
+		elog(ERROR, "expected to find SELECT subquery");
 	selectrte = rt_fetch(rtr->rtindex, parsetree->rtable);
-	selectquery = selectrte->subquery;
-	if (!(selectquery && IsA(selectquery, Query) &&
-		  selectquery->commandType == CMD_SELECT))
+	if (!(selectrte->rtekind == RTE_SUBQUERY &&
+		  selectrte->subquery &&
+		  IsA(selectrte->subquery, Query) &&
+		  selectrte->subquery->commandType == CMD_SELECT))
 		elog(ERROR, "expected to find SELECT subquery");
+	selectquery = selectrte->subquery;
 	if (list_length(selectquery->rtable) >= 2 &&
 		strcmp(rt_fetch(PRS2_OLD_VARNO, selectquery->rtable)->eref->aliasname,
 			   "old") == 0 &&
diff --git a/src/test/regress/expected/updatable_views.out b/src/test/regress/expected/updatable_views.out
@@ -3296,6 +3296,25 @@ select * from base_tab_def order by a, c NULLS LAST;
     | View default  |               | View default | 
 (22 rows)
 
+-- Test a DO ALSO INSERT ... SELECT rule
+drop rule base_tab_def_view_ins_rule on base_tab_def_view;
+create rule base_tab_def_view_ins_rule as on insert to base_tab_def_view
+  do also insert into base_tab_def (a, b, e) select new.a, new.b, 'xxx';
+truncate base_tab_def;
+insert into base_tab_def_view values (1, default, default, default, default);
+insert into base_tab_def_view values (2, default, default, default, default),
+                                     (3, default, default, default, default);
+select * from base_tab_def order by a, e nulls first;
+ a |      b       |       c       |      d       |  e  
+---+--------------+---------------+--------------+-----
+ 1 | View default | Table default | View default | 
+ 1 | View default | Table default |              | xxx
+ 2 | View default | Table default | View default | 
+ 2 | View default | Table default |              | xxx
+ 3 | View default | Table default | View default | 
+ 3 | View default | Table default |              | xxx
+(6 rows)
+
 drop view base_tab_def_view;
 drop table base_tab_def;
 -- Test defaults with array assignments
diff --git a/src/test/regress/sql/updatable_views.sql b/src/test/regress/sql/updatable_views.sql
@@ -1717,6 +1717,16 @@ insert into base_tab_def_view values (15, default, default, default, default),
 insert into base_tab_def_view values (17), (default);
 select * from base_tab_def order by a, c NULLS LAST;
 
+-- Test a DO ALSO INSERT ... SELECT rule
+drop rule base_tab_def_view_ins_rule on base_tab_def_view;
+create rule base_tab_def_view_ins_rule as on insert to base_tab_def_view
+  do also insert into base_tab_def (a, b, e) select new.a, new.b, 'xxx';
+truncate base_tab_def;
+insert into base_tab_def_view values (1, default, default, default, default);
+insert into base_tab_def_view values (2, default, default, default, default),
+                                     (3, default, default, default, default);
+select * from base_tab_def order by a, e nulls first;
+
 drop view base_tab_def_view;
 drop table base_tab_def;
 
