Revert MERGE patch

This reverts commits d204ef63776b8a00ca220adec23979091564e465,
83454e3c2b28141c0db01c7d2027e01040df5249 and a few more commits thereafter
(complete list at the end) related to MERGE feature.

While the feature was fully functional, with sufficient test coverage and
necessary documentation, it was felt that some parts of the executor and
parse-analyzer can use a different design and it wasn't possible to do that in
the available time. So it was decided to revert the patch for PG11 and retry
again in the future.

Thanks again to all reviewers and bug reporters.

List of commits reverted, in reverse chronological order:

 f1464c5380 Improve parse representation for MERGE
 ddb4158579 MERGE syntax diagram correction
 530e69e59b Allow cpluspluscheck to pass by renaming variable
 01b88b4df5 MERGE minor errata
 3af7b2b0d4 MERGE fix variable warning in non-assert builds
 a5d86181ec MERGE INSERT allows only one VALUES clause
 4b2d44031f MERGE post-commit review
 4923550c20 Tab completion for MERGE
 aa3faa3c7a WITH support in MERGE
 83454e3c2b New files for MERGE
 d204ef6377 MERGE SQL Command following SQL:2016

Author: Pavan Deolasee
Reviewed-by: Michael Paquier

1 files changed, 0 insertions, 97 deletions

diff --git a/src/backend/rewrite/rowsecurity.c b/src/backend/rewrite/rowsecurity.c
index 57e52b4f988..61ef396d8af 100644
--- a/src/backend/rewrite/rowsecurity.c
+++ b/src/backend/rewrite/rowsecurity.c
@@ -379,95 +379,6 @@ get_row_security_policies(Query *root, RangeTblEntry *rte, int rt_index,
 		}
 	}
 
-	/*
-	 * FOR MERGE, we fetch policies for UPDATE, DELETE and INSERT (and ALL)
-	 * and set them up so that we can enforce the appropriate policy depending
-	 * on the final action we take.
-	 *
-	 * We don't fetch the SELECT policies since they are correctly applied to
-	 * the root->mergeTarget_relation. The target rows are selected after
-	 * joining the mergeTarget_relation and the source relation and hence it's
-	 * enough to apply SELECT policies to the mergeTarget_relation.
-	 *
-	 * We don't push the UPDATE/DELETE USING quals to the RTE because we don't
-	 * really want to apply them while scanning the relation since we don't
-	 * know whether we will be doing a UPDATE or a DELETE at the end. We apply
-	 * the respective policy once we decide the final action on the target
-	 * tuple.
-	 *
-	 * XXX We are setting up USING quals as WITH CHECK. If RLS prohibits
-	 * UPDATE/DELETE on the target row, we shall throw an error instead of
-	 * silently ignoring the row. This is different than how normal
-	 * UPDATE/DELETE works and more in line with INSERT ON CONFLICT DO UPDATE
-	 * handling.
-	 */
-	if (commandType == CMD_MERGE)
-	{
-		List	   *merge_permissive_policies;
-		List	   *merge_restrictive_policies;
-
-		/*
-		 * Fetch the UPDATE policies and set them up to execute on the
-		 * existing target row before doing UPDATE.
-		 */
-		get_policies_for_relation(rel, CMD_UPDATE, user_id,
-								  &merge_permissive_policies,
-								  &merge_restrictive_policies);
-
-		/*
-		 * WCO_RLS_MERGE_UPDATE_CHECK is used to check UPDATE USING quals on
-		 * the existing target row.
-		 */
-		add_with_check_options(rel, rt_index,
-							   WCO_RLS_MERGE_UPDATE_CHECK,
-							   merge_permissive_policies,
-							   merge_restrictive_policies,
-							   withCheckOptions,
-							   hasSubLinks,
-							   true);
-
-		/*
-		 * Same with DELETE policies.
-		 */
-		get_policies_for_relation(rel, CMD_DELETE, user_id,
-								  &merge_permissive_policies,
-								  &merge_restrictive_policies);
-
-		add_with_check_options(rel, rt_index,
-							   WCO_RLS_MERGE_DELETE_CHECK,
-							   merge_permissive_policies,
-							   merge_restrictive_policies,
-							   withCheckOptions,
-							   hasSubLinks,
-							   true);
-
-		/*
-		 * No special handling is required for INSERT policies. They will be
-		 * checked and enforced during ExecInsert(). But we must add them to
-		 * withCheckOptions.
-		 */
-		get_policies_for_relation(rel, CMD_INSERT, user_id,
-								  &merge_permissive_policies,
-								  &merge_restrictive_policies);
-
-		add_with_check_options(rel, rt_index,
-							   WCO_RLS_INSERT_CHECK,
-							   merge_permissive_policies,
-							   merge_restrictive_policies,
-							   withCheckOptions,
-							   hasSubLinks,
-							   false);
-
-		/* Enforce the WITH CHECK clauses of the UPDATE policies */
-		add_with_check_options(rel, rt_index,
-							   WCO_RLS_UPDATE_CHECK,
-							   merge_permissive_policies,
-							   merge_restrictive_policies,
-							   withCheckOptions,
-							   hasSubLinks,
-							   false);
-	}
-
 	heap_close(rel, NoLock);
 
 	/*
@@ -527,14 +438,6 @@ get_policies_for_relation(Relation relation, CmdType cmd, Oid user_id,
 					if (policy->polcmd == ACL_DELETE_CHR)
 						cmd_matches = true;
 					break;
-				case CMD_MERGE:
-
-					/*
-					 * We do not support a separate policy for MERGE command.
-					 * Instead it derives from the policies defined for other
-					 * commands.
-					 */
-					break;
 				default:
 					elog(ERROR, "unrecognized policy command type %d",
 						 (int) cmd);