Support MERGE into updatable views.

This allows the target relation of MERGE to be an auto-updatable or
trigger-updatable view, and includes support for WITH CHECK OPTION,
security barrier views, and security invoker views.

A trigger-updatable view must have INSTEAD OF triggers for every type
of action (INSERT, UPDATE, and DELETE) mentioned in the MERGE command.
An auto-updatable view must not have any INSTEAD OF triggers. Mixing
auto-update and trigger-update actions (i.e., having a partial set of
INSTEAD OF triggers) is not supported.

Rule-updatable views are also not supported, since there is no
rewriter support for non-SELECT rules with MERGE operations.

Dean Rasheed, reviewed by Jian He and Alvaro Herrera.

Discussion: https://postgr.es/m/CAEZATCVcB1g0nmxuEc-A+gGB0HnfcGQNGYH7gS=7rq0u0zOBXA@mail.gmail.com

1 files changed, 14 insertions, 37 deletions

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 13a9b7da83b..79ef46f2614 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -56,6 +56,7 @@
 #include "miscadmin.h"
 #include "parser/parse_relation.h"
 #include "parser/parsetree.h"
+#include "rewrite/rewriteHandler.h"
 #include "storage/bufmgr.h"
 #include "storage/lmgr.h"
 #include "tcop/utility.h"
@@ -1017,14 +1018,18 @@ InitPlan(QueryDesc *queryDesc, int eflags)
  * Generally the parser and/or planner should have noticed any such mistake
  * already, but let's make sure.
  *
+ * For MERGE, mergeActions is the list of actions that may be performed.  The
+ * result relation is required to support every action, regardless of whether
+ * or not they are all executed.
+ *
  * Note: when changing this function, you probably also need to look at
  * CheckValidRowMarkRel.
  */
 void
-CheckValidResultRel(ResultRelInfo *resultRelInfo, CmdType operation)
+CheckValidResultRel(ResultRelInfo *resultRelInfo, CmdType operation,
+					List *mergeActions)
 {
 	Relation	resultRel = resultRelInfo->ri_RelationDesc;
-	TriggerDesc *trigDesc = resultRel->trigdesc;
 	FdwRoutine *fdwroutine;
 
 	switch (resultRel->rd_rel->relkind)
@@ -1048,42 +1053,14 @@ CheckValidResultRel(ResultRelInfo *resultRelInfo, CmdType operation)
 		case RELKIND_VIEW:
 
 			/*
-			 * Okay only if there's a suitable INSTEAD OF trigger.  Messages
-			 * here should match rewriteHandler.c's rewriteTargetView and
-			 * RewriteQuery, except that we omit errdetail because we haven't
-			 * got the information handy (and given that we really shouldn't
-			 * get here anyway, it's not worth great exertion to get).
+			 * Okay only if there's a suitable INSTEAD OF trigger.  Otherwise,
+			 * complain, but omit errdetail because we haven't got the
+			 * information handy (and given that it really shouldn't happen,
+			 * it's not worth great exertion to get).
 			 */
-			switch (operation)
-			{
-				case CMD_INSERT:
-					if (!trigDesc || !trigDesc->trig_insert_instead_row)
-						ereport(ERROR,
-								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-								 errmsg("cannot insert into view \"%s\"",
-										RelationGetRelationName(resultRel)),
-								 errhint("To enable inserting into the view, provide an INSTEAD OF INSERT trigger or an unconditional ON INSERT DO INSTEAD rule.")));
-					break;
-				case CMD_UPDATE:
-					if (!trigDesc || !trigDesc->trig_update_instead_row)
-						ereport(ERROR,
-								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-								 errmsg("cannot update view \"%s\"",
-										RelationGetRelationName(resultRel)),
-								 errhint("To enable updating the view, provide an INSTEAD OF UPDATE trigger or an unconditional ON UPDATE DO INSTEAD rule.")));
-					break;
-				case CMD_DELETE:
-					if (!trigDesc || !trigDesc->trig_delete_instead_row)
-						ereport(ERROR,
-								(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
-								 errmsg("cannot delete from view \"%s\"",
-										RelationGetRelationName(resultRel)),
-								 errhint("To enable deleting from the view, provide an INSTEAD OF DELETE trigger or an unconditional ON DELETE DO INSTEAD rule.")));
-					break;
-				default:
-					elog(ERROR, "unrecognized CmdType: %d", (int) operation);
-					break;
-			}
+			if (!view_has_instead_trigger(resultRel, operation, mergeActions))
+				error_view_not_updatable(resultRel, operation, mergeActions,
+										 NULL);
 			break;
 		case RELKIND_MATVIEW:
 			if (!MatViewIncrementalMaintenanceIsEnabled())