Implement latest Naisila's comments

src/backend/distributed/commands/multi_copy.c

@@ -2830,18 +2830,21 @@ CopyStatementHasFormat(CopyStmt *copyStatement, char *formatName)
 
 
 /*
- * ErrorIfMergeInCopy Raises an exception if the MERGE is called in the COPY.
+ * ErrorIfMergeInCopy Raises an exception if the MERGE is called in the COPY
+ * where Citus tables are involved, as we don't support this yet
+ * Relevant PG17 commit: c649fa24a
  */
 static void
 ErrorIfMergeInCopy(CopyStmt *copyStatement)
 {
-#if PG_VERSION_NUM < 150000
+#if PG_VERSION_NUM < 170000
 	return;
 #else
 	if (!copyStatement->relation && (IsA(copyStatement->query, MergeStmt)))
 	{
 		ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-						errmsg("MERGE not supported in COPY")));
+						errmsg("MERGE with Citus tables "
+							   "is not yet supported in COPY")));
 	}
 #endif
 }

src/backend/distributed/planner/merge_planner.c

@@ -173,6 +173,7 @@ GetMergeJoinTree(Query *mergeQuery)
 	 * jointree with an empty fromlist. This works because the fromlist of a merge query
 	 * join tree consists of range table references only, and range table references are
 	 * disregarded by the WhereClauseList() walker.
+	 * Relevant PG17 commit: 0294df2f1
 	 */
 	mergeJointree = makeFromExpr(NIL, mergeQuery->mergeJoinCondition);
 #else
@@ -995,15 +996,17 @@ ConvertSourceRTEIntoSubquery(Query *mergeQuery, RangeTblEntry *sourceRte,
 
 
 /*
- * ErrorIfMergeHasReturningList raises an exception if the MERGE
+ * ErrorIfMergeHasReturningList raises an exception if the MERGE has
- * has a RETURNING clause.
+ * a RETURNING clause, as we don't support this yet for Citus tables
+ * Relevant PG17 commit: c649fa24a
  */
 static void
 ErrorIfMergeHasReturningList(Query *query)
 {
 	if (query->returningList)
 	{
-		ereport(ERROR, (errmsg("MERGE with RETURNING is not yet supported")));
+		ereport(ERROR, (errmsg("MERGE with RETURNING is not yet supported "
+							   "for Citus tables")));
 	}
 }
 

src/test/regress/expected/merge_unsupported.out

@@ -1,4 +1,15 @@
 SHOW server_version \gset
+SELECT CASE
+           WHEN substring(current_setting('server_version'), '\d+')::int >= 17 THEN '17+'
+           WHEN substring(current_setting('server_version'), '\d+')::int IN (15, 16) THEN '15_16'
+           WHEN substring(current_setting('server_version'), '\d+')::int = 14 THEN '14'
+           ELSE 'Unsupported version'
+       END AS version_category;
+ version_category
+---------------------------------------------------------------------
+ 17+
+(1 row)
+
 SELECT substring(:'server_version', '\d+')::int >= 15 AS server_version_ge_15
 \gset
 \if :server_version_ge_15
@@ -13,26 +24,10 @@ NOTICE:  schema "pgmerge_schema" does not exist, skipping
 CREATE SCHEMA pgmerge_schema;
 SET search_path TO pgmerge_schema;
 SET citus.use_citus_managed_tables to true;
-DROP TABLE IF EXISTS target;
-NOTICE:  table "target" does not exist, skipping
-DROP TABLE IF EXISTS source;
-NOTICE:  table "source" does not exist, skipping
 CREATE TABLE target (tid integer, balance integer)
   WITH (autovacuum_enabled=off);
 CREATE TABLE source (sid integer, delta integer) -- no index
   WITH (autovacuum_enabled=off);
-SELECT citus_add_local_table_to_metadata('target');
- citus_add_local_table_to_metadata
----------------------------------------------------------------------
-
-(1 row)
-
-SELECT citus_add_local_table_to_metadata('source');
- citus_add_local_table_to_metadata
----------------------------------------------------------------------
-
-(1 row)
-
 \set SHOW_CONTEXT errors
 -- used in a CTE
 WITH foo AS (
@@ -45,19 +40,19 @@ COPY (
   MERGE INTO target USING source ON (true)
   WHEN MATCHED THEN DELETE
 ) TO stdout;
-ERROR:  MERGE not supported in COPY
+ERROR:  MERGE with Citus tables is not yet supported in COPY
 -- used in a CTE with RETURNING
 WITH foo AS (
   MERGE INTO target USING source ON (true)
   WHEN MATCHED THEN DELETE RETURNING target.*
 ) SELECT * FROM foo;
-ERROR:  MERGE with RETURNING is not yet supported
+ERROR:  MERGE with RETURNING is not yet supported for Citus tables
 -- used in COPY with RETURNING
 COPY (
   MERGE INTO target USING source ON (true)
   WHEN MATCHED THEN DELETE RETURNING target.*
 ) TO stdout;
-ERROR:  MERGE not supported in COPY
+ERROR:  MERGE with Citus tables is not yet supported in COPY
 -- unsupported relation types
 -- view
 CREATE VIEW tv AS SELECT count(tid) AS tid FROM target;
@@ -102,5 +97,5 @@ WHEN NOT MATCHED THEN
 WHEN MATCHED AND tid < 2 THEN
         DELETE
 RETURNING *;
-ERROR:  MERGE with RETURNING is not yet supported
+ERROR:  MERGE with RETURNING is not yet supported for Citus tables
 ROLLBACK;

src/test/regress/expected/merge_unsupported_0.out

@@ -1,4 +1,15 @@
 SHOW server_version \gset
+SELECT CASE
+           WHEN substring(current_setting('server_version'), '\d+')::int >= 17 THEN '17+'
+           WHEN substring(current_setting('server_version'), '\d+')::int IN (15, 16) THEN '15_16'
+           WHEN substring(current_setting('server_version'), '\d+')::int = 14 THEN '14'
+           ELSE 'Unsupported version'
+       END AS version_category;
+ version_category
+---------------------------------------------------------------------
+ 15_16
+(1 row)
+
 SELECT substring(:'server_version', '\d+')::int >= 15 AS server_version_ge_15
 \gset
 \if :server_version_ge_15
@@ -13,26 +24,10 @@ NOTICE:  schema "pgmerge_schema" does not exist, skipping
 CREATE SCHEMA pgmerge_schema;
 SET search_path TO pgmerge_schema;
 SET citus.use_citus_managed_tables to true;
-DROP TABLE IF EXISTS target;
-NOTICE:  table "target" does not exist, skipping
-DROP TABLE IF EXISTS source;
-NOTICE:  table "source" does not exist, skipping
 CREATE TABLE target (tid integer, balance integer)
   WITH (autovacuum_enabled=off);
 CREATE TABLE source (sid integer, delta integer) -- no index
   WITH (autovacuum_enabled=off);
-SELECT citus_add_local_table_to_metadata('target');
- citus_add_local_table_to_metadata
----------------------------------------------------------------------
-
-(1 row)
-
-SELECT citus_add_local_table_to_metadata('source');
- citus_add_local_table_to_metadata
----------------------------------------------------------------------
-
-(1 row)
-
 \set SHOW_CONTEXT errors
 -- used in a CTE
 WITH foo AS (

src/test/regress/expected/merge_unsupported_1.out

@@ -1,4 +1,15 @@
 SHOW server_version \gset
+SELECT CASE
+           WHEN substring(current_setting('server_version'), '\d+')::int >= 17 THEN '17+'
+           WHEN substring(current_setting('server_version'), '\d+')::int IN (15, 16) THEN '15_16'
+           WHEN substring(current_setting('server_version'), '\d+')::int = 14 THEN '14'
+           ELSE 'Unsupported version'
+       END AS version_category;
+ version_category
+---------------------------------------------------------------------
+ 14
+(1 row)
+
 SELECT substring(:'server_version', '\d+')::int >= 15 AS server_version_ge_15
 \gset
 \if :server_version_ge_15

src/test/regress/expected/pg15.out

@@ -437,11 +437,6 @@ MERGE INTO tbl1 USING targq ON (true)
 WHEN MATCHED THEN DELETE;
 ERROR:  The required join operation is missing between the target's distribution column and any expression originating from the source. The issue may arise from a non-equi-join.
 DETAIL:  Without a equi-join condition on the target's distribution column, the source rows cannot be efficiently redistributed, and the NOT-MATCHED condition cannot be evaluated unambiguously. This can result in incorrect or unexpected results when attempting to merge tables in a distributed setting
-COPY (
-  MERGE INTO tbl1 USING tbl2 ON (true)
-  WHEN MATCHED THEN DELETE
-) TO stdout;
-ERROR:  MERGE not supported in COPY
 MERGE INTO tbl1 t
 USING tbl2
 ON (true)

src/test/regress/expected/pgmerge.out

@@ -167,7 +167,7 @@ COPY (
   MERGE INTO target USING source ON (true)
   WHEN MATCHED THEN DELETE
 ) TO stdout;
-ERROR:  MERGE not supported in COPY
+ERROR:  MERGE with Citus tables is not yet supported in COPY
 -- unsupported relation types
 -- materialized view
 CREATE MATERIALIZED VIEW mv AS SELECT * FROM target;

src/test/regress/sql/merge_unsupported.sql

@@ -1,6 +1,12 @@
 
 
 SHOW server_version \gset
+SELECT CASE
+           WHEN substring(current_setting('server_version'), '\d+')::int >= 17 THEN '17+'
+           WHEN substring(current_setting('server_version'), '\d+')::int IN (15, 16) THEN '15_16'
+           WHEN substring(current_setting('server_version'), '\d+')::int = 14 THEN '14'
+           ELSE 'Unsupported version'
+       END AS version_category;
 SELECT substring(:'server_version', '\d+')::int >= 15 AS server_version_ge_15
 \gset
 \if :server_version_ge_15
@@ -17,17 +23,11 @@ SET search_path TO pgmerge_schema;
 
 SET citus.use_citus_managed_tables to true;
 
-DROP TABLE IF EXISTS target;
-DROP TABLE IF EXISTS source;
 CREATE TABLE target (tid integer, balance integer)
   WITH (autovacuum_enabled=off);
 CREATE TABLE source (sid integer, delta integer) -- no index
   WITH (autovacuum_enabled=off);
 
-SELECT citus_add_local_table_to_metadata('target');
-SELECT citus_add_local_table_to_metadata('source');
-
-
 \set SHOW_CONTEXT errors
 -- used in a CTE
 WITH foo AS (

src/test/regress/sql/pg15.sql

@@ -287,11 +287,6 @@ WITH targq AS (
 MERGE INTO tbl1 USING targq ON (true)
 WHEN MATCHED THEN DELETE;
 
-COPY (
-  MERGE INTO tbl1 USING tbl2 ON (true)
-  WHEN MATCHED THEN DELETE
-) TO stdout;
-
 MERGE INTO tbl1 t
 USING tbl2
 ON (true)