pgsql: Revert MERGE patch

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

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/08ea7a2291db21a618d19d612c8060cda68f1892

Modified Files
--------------
contrib/test_decoding/expected/ddl.out | 46 -
contrib/test_decoding/sql/ddl.sql | 16 -
doc/src/sgml/libpq.sgml | 8 +-
doc/src/sgml/mvcc.sgml | 28 +-
doc/src/sgml/plpgsql.sgml | 3 +-
doc/src/sgml/ref/allfiles.sgml | 1 -
doc/src/sgml/ref/create_policy.sgml | 7 -
doc/src/sgml/ref/insert.sgml | 11 +-
doc/src/sgml/ref/merge.sgml | 617 --------
doc/src/sgml/reference.sgml | 1 -
doc/src/sgml/trigger.sgml | 20 -
src/backend/access/heap/heapam.c | 28 +-
src/backend/catalog/sql_features.txt | 6 +-
src/backend/commands/explain.c | 33 -
src/backend/commands/prepare.c | 1 -
src/backend/commands/trigger.c | 270 +---
src/backend/executor/Makefile | 2 +-
src/backend/executor/README | 11 -
src/backend/executor/execMain.c | 17 -
src/backend/executor/execMerge.c | 682 --------
src/backend/executor/execPartition.c | 121 --
src/backend/executor/execReplication.c | 4 +-
src/backend/executor/nodeModifyTable.c | 280 +---
src/backend/executor/spi.c | 3 -
src/backend/nodes/copyfuncs.c | 58 -
src/backend/nodes/equalfuncs.c | 49 -
src/backend/nodes/nodeFuncs.c | 64 +-
src/backend/nodes/outfuncs.c | 40 -
src/backend/nodes/readfuncs.c | 45 -
src/backend/optimizer/plan/createplan.c | 22 +-
src/backend/optimizer/plan/planner.c | 29 +-
src/backend/optimizer/plan/setrefs.c | 54 -
src/backend/optimizer/prep/preptlist.c | 41 -
src/backend/optimizer/util/pathnode.c | 11 +-
src/backend/optimizer/util/plancat.c | 4 -
src/backend/parser/Makefile | 2 +-
src/backend/parser/analyze.c | 18 +-
src/backend/parser/gram.y | 151 +-
src/backend/parser/parse_agg.c | 10 -
src/backend/parser/parse_clause.c | 57 +-
src/backend/parser/parse_collate.c | 1 -
src/backend/parser/parse_expr.c | 3 -
src/backend/parser/parse_func.c | 3 -
src/backend/parser/parse_merge.c | 654 --------
src/backend/parser/parse_relation.c | 10 -
src/backend/rewrite/rewriteHandler.c | 115 +-
src/backend/rewrite/rowsecurity.c | 97 --
src/backend/tcop/pquery.c | 5 -
src/backend/tcop/utility.c | 16 -
src/bin/psql/tab-complete.c | 87 +-
src/include/access/heapam.h | 13 +-
src/include/commands/trigger.h | 6 +-
src/include/executor/execMerge.h | 31 -
src/include/executor/execPartition.h | 1 -
src/include/executor/instrument.h | 7 +-
src/include/executor/nodeModifyTable.h | 23 -
src/include/executor/spi.h | 1 -
src/include/nodes/execnodes.h | 65 +-
src/include/nodes/nodes.h | 7 +-
src/include/nodes/parsenodes.h | 53 +-
src/include/nodes/plannodes.h | 8 +-
src/include/nodes/relation.h | 7 +-
src/include/optimizer/pathnode.h | 7 +-
src/include/parser/analyze.h | 5 -
src/include/parser/kwlist.h | 2 -
src/include/parser/parse_clause.h | 5 +-
src/include/parser/parse_merge.h | 19 -
src/include/parser/parse_node.h | 5 +-
src/include/rewrite/rewriteHandler.h | 1 -
src/interfaces/libpq/fe-exec.c | 9 +-
src/pl/plpgsql/src/pl_exec.c | 5 +-
src/pl/plpgsql/src/pl_gram.y | 8 -
src/pl/plpgsql/src/pl_scanner.c | 1 -
src/pl/plpgsql/src/plpgsql.h | 4 +-
src/test/isolation/expected/merge-delete.out | 97 --
.../isolation/expected/merge-insert-update.out | 84 -
.../isolation/expected/merge-match-recheck.out | 106 --
src/test/isolation/expected/merge-update.out | 238 ---
src/test/isolation/isolation_schedule | 4 -
src/test/isolation/specs/merge-delete.spec | 51 -
src/test/isolation/specs/merge-insert-update.spec | 52 -
src/test/isolation/specs/merge-match-recheck.spec | 79 -
src/test/isolation/specs/merge-update.spec | 133 --
src/test/regress/expected/identity.out | 55 -
src/test/regress/expected/merge.out | 1672 --------------------
src/test/regress/expected/privileges.out | 98 --
src/test/regress/expected/rowsecurity.out | 182 ---
src/test/regress/expected/rules.out | 31 -
src/test/regress/expected/triggers.out | 48 -
src/test/regress/expected/with.out | 137 --
src/test/regress/parallel_schedule | 2 +-
src/test/regress/serial_schedule | 1 -
src/test/regress/sql/identity.sql | 45 -
src/test/regress/sql/merge.sql | 1173 --------------
src/test/regress/sql/privileges.sql | 108 --
src/test/regress/sql/rowsecurity.sql | 156 --
src/test/regress/sql/rules.sql | 33 -
src/test/regress/sql/triggers.sql | 47 -
src/test/regress/sql/with.sql | 56 -
src/tools/pgindent/typedefs.list | 3 -
100 files changed, 217 insertions(+), 8629 deletions(-)