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, 6 deletions

diff --git a/src/backend/rewrite/rewriteManip.c b/src/backend/rewrite/rewriteManip.c
index 76c97a5b28e..191f2dc0b1d 100644
--- a/src/backend/rewrite/rewriteManip.c
+++ b/src/backend/rewrite/rewriteManip.c
@@ -496,9 +496,10 @@ OffsetVarNodes(Node *node, int offset, int sublevels_up)
 		/*
 		 * If we are starting at a Query, and sublevels_up is zero, then we
 		 * must also fix rangetable indexes in the Query itself --- namely
-		 * resultRelation, exclRelIndex and rowMarks entries.  sublevels_up
-		 * cannot be zero when recursing into a subquery, so there's no need
-		 * to have the same logic inside OffsetVarNodes_walker.
+		 * resultRelation, mergeTargetRelation, exclRelIndex and rowMarks
+		 * entries.  sublevels_up cannot be zero when recursing into a
+		 * subquery, so there's no need to have the same logic inside
+		 * OffsetVarNodes_walker.
 		 */
 		if (sublevels_up == 0)
 		{
@@ -507,6 +508,9 @@ OffsetVarNodes(Node *node, int offset, int sublevels_up)
 			if (qry->resultRelation)
 				qry->resultRelation += offset;
 
+			if (qry->mergeTargetRelation)
+				qry->mergeTargetRelation += offset;
+
 			if (qry->onConflict && qry->onConflict->exclRelIndex)
 				qry->onConflict->exclRelIndex += offset;
 
@@ -687,9 +691,10 @@ ChangeVarNodes(Node *node, int rt_index, int new_index, int sublevels_up)
 		/*
 		 * If we are starting at a Query, and sublevels_up is zero, then we
 		 * must also fix rangetable indexes in the Query itself --- namely
-		 * resultRelation and rowMarks entries.  sublevels_up cannot be zero
-		 * when recursing into a subquery, so there's no need to have the same
-		 * logic inside ChangeVarNodes_walker.
+		 * resultRelation, mergeTargetRelation, exclRelIndex  and rowMarks
+		 * entries.  sublevels_up cannot be zero when recursing into a
+		 * subquery, so there's no need to have the same logic inside
+		 * ChangeVarNodes_walker.
 		 */
 		if (sublevels_up == 0)
 		{
@@ -698,6 +703,9 @@ ChangeVarNodes(Node *node, int rt_index, int new_index, int sublevels_up)
 			if (qry->resultRelation == rt_index)
 				qry->resultRelation = new_index;
 
+			if (qry->mergeTargetRelation == rt_index)
+				qry->mergeTargetRelation = new_index;
+
 			/* this is unlikely to ever be used, but ... */
 			if (qry->onConflict && qry->onConflict->exclRelIndex == rt_index)
 				qry->onConflict->exclRelIndex = new_index;