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

2 files changed, 0 insertions, 62 deletions

diff --git a/contrib/test_decoding/expected/ddl.out b/contrib/test_decoding/expected/ddl.out
index 79c359d6e3d..b7c76469fc3 100644
--- a/contrib/test_decoding/expected/ddl.out
+++ b/contrib/test_decoding/expected/ddl.out
@@ -192,52 +192,6 @@ SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'inc
  COMMIT
 (33 rows)
 
--- MERGE support
-BEGIN;
-MERGE INTO replication_example t
-	USING (SELECT i as id, i as data, i as num FROM generate_series(-20, 5) i) s
-	ON t.id = s.id
-	WHEN MATCHED AND t.id < 0 THEN
-		UPDATE SET somenum = somenum + 1
-	WHEN MATCHED AND t.id >= 0 THEN
-		DELETE
-	WHEN NOT MATCHED THEN
-		INSERT VALUES (s.*);
-COMMIT;
-/* display results */
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
-                                                                       data                                                                       
---------------------------------------------------------------------------------------------------------------------------------------------------
- BEGIN
- table public.replication_example: INSERT: id[integer]:-20 somedata[integer]:-20 somenum[integer]:-20 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: INSERT: id[integer]:-19 somedata[integer]:-19 somenum[integer]:-19 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: INSERT: id[integer]:-18 somedata[integer]:-18 somenum[integer]:-18 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: INSERT: id[integer]:-17 somedata[integer]:-17 somenum[integer]:-17 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: INSERT: id[integer]:-16 somedata[integer]:-16 somenum[integer]:-16 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-15 somedata[integer]:-15 somenum[integer]:-14 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-14 somedata[integer]:-14 somenum[integer]:-13 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-13 somedata[integer]:-13 somenum[integer]:-12 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-12 somedata[integer]:-12 somenum[integer]:-11 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-11 somedata[integer]:-11 somenum[integer]:-10 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-10 somedata[integer]:-10 somenum[integer]:-9 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-9 somedata[integer]:-9 somenum[integer]:-8 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-8 somedata[integer]:-8 somenum[integer]:-7 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-7 somedata[integer]:-7 somenum[integer]:-6 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-6 somedata[integer]:-6 somenum[integer]:-5 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-5 somedata[integer]:-5 somenum[integer]:-4 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-4 somedata[integer]:-4 somenum[integer]:-3 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-3 somedata[integer]:-3 somenum[integer]:-2 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-2 somedata[integer]:-2 somenum[integer]:-1 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: UPDATE: id[integer]:-1 somedata[integer]:-1 somenum[integer]:0 zaphod1[integer]:null zaphod2[integer]:null
- table public.replication_example: DELETE: id[integer]:0
- table public.replication_example: DELETE: id[integer]:1
- table public.replication_example: DELETE: id[integer]:2
- table public.replication_example: DELETE: id[integer]:3
- table public.replication_example: DELETE: id[integer]:4
- table public.replication_example: DELETE: id[integer]:5
- COMMIT
-(28 rows)
-
 CREATE TABLE tr_unique(id2 serial unique NOT NULL, data int);
 INSERT INTO tr_unique(data) VALUES(10);
 ALTER TABLE tr_unique RENAME TO tr_pkey;
diff --git a/contrib/test_decoding/sql/ddl.sql b/contrib/test_decoding/sql/ddl.sql
index 0e608b252fa..c4b10a4cf9e 100644
--- a/contrib/test_decoding/sql/ddl.sql
+++ b/contrib/test_decoding/sql/ddl.sql
@@ -93,22 +93,6 @@ COMMIT;
 /* display results */
 SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
 
--- MERGE support
-BEGIN;
-MERGE INTO replication_example t
-	USING (SELECT i as id, i as data, i as num FROM generate_series(-20, 5) i) s
-	ON t.id = s.id
-	WHEN MATCHED AND t.id < 0 THEN
-		UPDATE SET somenum = somenum + 1
-	WHEN MATCHED AND t.id >= 0 THEN
-		DELETE
-	WHEN NOT MATCHED THEN
-		INSERT VALUES (s.*);
-COMMIT;
-
-/* display results */
-SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
-
 CREATE TABLE tr_unique(id2 serial unique NOT NULL, data int);
 INSERT INTO tr_unique(data) VALUES(10);
 ALTER TABLE tr_unique RENAME TO tr_pkey;