Support MERGE command for single_shard_distributed Target (#7643)

This PR has following changes :
1. Enable MERGE command for single_shard_distributed targets.

src/backend/distributed/commands/multi_copy.c

@@ -2568,7 +2568,7 @@ ShardIdForTuple(CitusCopyDestReceiver *copyDest, Datum *columnValues, bool *colu
 	 * Find the shard interval and id for the partition column value for
 	 * non-reference tables.
 	 *
-	 * For reference table, this function blindly returns the tables single
+	 * For reference table, and single shard distributed table this function blindly returns the tables single
 	 * shard.
 	 */
 	ShardInterval *shardInterval = FindShardInterval(partitionColumnValue, cacheEntry);

src/backend/distributed/planner/merge_planner.c

@@ -243,14 +243,27 @@ CreateNonPushableMergePlan(Oid targetRelationId, uint64 planId, Query *originalQ
 
 	CitusTableCacheEntry *targetRelation = GetCitusTableCacheEntry(targetRelationId);
 
-	/*
-	 * Get the index of the column in the source query that will be utilized
-	 * to repartition the source rows, ensuring colocation with the target
-	 */
-	distributedPlan->sourceResultRepartitionColumnIndex =
-		SourceResultPartitionColumnIndex(mergeQuery,
-										 sourceQuery->targetList,
-										 targetRelation);
+
+	if (IsCitusTableType(targetRelation->relationId, SINGLE_SHARD_DISTRIBUTED))
+	{
+		/*
+		 * if target table is SINGLE_SHARD_DISTRIBUTED let's set this to invalid -1
+		 * so later in execution phase we don't rely on this value and try to find single shard of target instead.
+		 */
+		distributedPlan->sourceResultRepartitionColumnIndex = -1;
+	}
+	else
+	{
+		/*
+		 * Get the index of the column in the source query that will be utilized
+		 * to repartition the source rows, ensuring colocation with the target
+		 */
+
+		distributedPlan->sourceResultRepartitionColumnIndex =
+			SourceResultPartitionColumnIndex(mergeQuery,
+											 sourceQuery->targetList,
+											 targetRelation);
+	}
 
 	/*
 	 * Make a copy of the source query, since following code scribbles it
@@ -262,11 +275,11 @@ CreateNonPushableMergePlan(Oid targetRelationId, uint64 planId, Query *originalQ
 	int cursorOptions = CURSOR_OPT_PARALLEL_OK;
 	PlannedStmt *sourceRowsPlan = pg_plan_query(sourceQueryCopy, NULL, cursorOptions,
 												boundParams);
-	bool repartitioned = IsRedistributablePlan(sourceRowsPlan->planTree) &&
-						 IsSupportedRedistributionTarget(targetRelationId);
+	bool isRepartitionAllowed = IsRedistributablePlan(sourceRowsPlan->planTree) &&
+								IsSupportedRedistributionTarget(targetRelationId);
 
 	/* If plan is distributed, no work at the coordinator */
-	if (repartitioned)
+	if (isRepartitionAllowed)
 	{
 		distributedPlan->modifyWithSelectMethod = MODIFY_WITH_SELECT_REPARTITION;
 	}
@@ -1273,13 +1286,6 @@ static int
 SourceResultPartitionColumnIndex(Query *mergeQuery, List *sourceTargetList,
 								 CitusTableCacheEntry *targetRelation)
 {
-	if (IsCitusTableType(targetRelation->relationId, SINGLE_SHARD_DISTRIBUTED))
-	{
-		ereport(ERROR, (errmsg("MERGE operation across distributed schemas "
-							   "or with a row-based distributed table is "
-							   "not yet supported")));
-	}
-
 	/* Get all the Join conditions from the ON clause */
 	List *mergeJoinConditionList = WhereClauseList(mergeQuery->jointree);
 	Var *targetColumn = targetRelation->partitionColumn;

src/test/regress/bin/normalize.sed

@@ -32,6 +32,7 @@ s/"t2_[0-9]+"/"t2_xxxxxxx"/g
 # shard table names for MERGE tests
 s/merge_schema\.([_a-z0-9]+)_40[0-9]+ /merge_schema.\1_xxxxxxx /g
 s/pgmerge_schema\.([_a-z0-9]+)_40[0-9]+ /pgmerge_schema.\1_xxxxxxx /g
+s/merge_vcore_schema\.([_a-z0-9]+)_40[0-9]+ /pgmerge_schema.\1_xxxxxxx /g
 
 # shard table names for multi_subquery
 s/ keyval(1|2|ref)_[0-9]+ / keyval\1_xxxxxxx /g

src/test/regress/expected/merge_schema_sharding.out

@@ -98,14 +98,26 @@ WHEN MATCHED THEN UPDATE SET b = nullkey_c2_t1.b;
 DEBUG:  Distributed tables are not co-located, try repartitioning
 DEBUG:  For MERGE command, all the distributed tables must be colocated
 DEBUG:  Creating MERGE repartition plan
-ERROR:  MERGE operation across distributed schemas or with a row-based distributed table is not yet supported
+DEBUG:  Distributed planning for a fast-path router query
+DEBUG:  Creating router plan
+DEBUG:  Collect source query results on coordinator
+DEBUG:  Create a MERGE task list that needs to be routed
+DEBUG:  <Deparsed MERGE query: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) nullkey_c2_t1 ON (citus_table_alias.a OPERATOR(pg_catalog.=) nullkey_c2_t1.a) WHEN MATCHED THEN UPDATE SET b = nullkey_c2_t1.b>
+DEBUG:  distributed statement: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) nullkey_c2_t1 ON (citus_table_alias.a OPERATOR(pg_catalog.=) nullkey_c2_t1.a) WHEN MATCHED THEN UPDATE SET b = nullkey_c2_t1.b
+DEBUG:  Execute MERGE task list
 MERGE INTO schema_shard_table1.nullkey_c1_t1 USING nullkey_c2_t1 ON (schema_shard_table1.nullkey_c1_t1.a = nullkey_c2_t1.a)
 WHEN MATCHED THEN UPDATE SET b = nullkey_c2_t1.b
 WHEN NOT MATCHED THEN INSERT VALUES (nullkey_c2_t1.a, nullkey_c2_t1.b);
 DEBUG:  Distributed tables are not co-located, try repartitioning
 DEBUG:  For MERGE command, all the distributed tables must be colocated
 DEBUG:  Creating MERGE repartition plan
-ERROR:  MERGE operation across distributed schemas or with a row-based distributed table is not yet supported
+DEBUG:  Distributed planning for a fast-path router query
+DEBUG:  Creating router plan
+DEBUG:  Collect source query results on coordinator
+DEBUG:  Create a MERGE task list that needs to be routed
+DEBUG:  <Deparsed MERGE query: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) nullkey_c2_t1 ON (citus_table_alias.a OPERATOR(pg_catalog.=) nullkey_c2_t1.a) WHEN MATCHED THEN UPDATE SET b = nullkey_c2_t1.b WHEN NOT MATCHED THEN INSERT (a, b) VALUES (nullkey_c2_t1.a, nullkey_c2_t1.b)>
+DEBUG:  distributed statement: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) nullkey_c2_t1 ON (citus_table_alias.a OPERATOR(pg_catalog.=) nullkey_c2_t1.a) WHEN MATCHED THEN UPDATE SET b = nullkey_c2_t1.b WHEN NOT MATCHED THEN INSERT (a, b) VALUES (nullkey_c2_t1.a, nullkey_c2_t1.b)
+DEBUG:  Execute MERGE task list
 -- with a distributed table
 SET search_path TO schema_shard_table1;
 MERGE INTO nullkey_c1_t1 USING schema_shard_table.distributed_table ON (nullkey_c1_t1.a = schema_shard_table.distributed_table.a)
@@ -114,7 +126,12 @@ WHEN NOT MATCHED THEN INSERT VALUES (schema_shard_table.distributed_table.a, sch
 DEBUG:  Distributed tables are not co-located, try repartitioning
 DEBUG:  For MERGE command, all the distributed tables must be colocated
 DEBUG:  Creating MERGE repartition plan
-ERROR:  MERGE operation across distributed schemas or with a row-based distributed table is not yet supported
+DEBUG:  Router planner cannot handle multi-shard select queries
+DEBUG:  Collect source query results on coordinator
+DEBUG:  Create a MERGE task list that needs to be routed
+DEBUG:  <Deparsed MERGE query: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) distributed_table ON (citus_table_alias.a OPERATOR(pg_catalog.=) distributed_table.a) WHEN MATCHED THEN UPDATE SET b = distributed_table.b WHEN NOT MATCHED THEN INSERT (a, b) VALUES (distributed_table.a, distributed_table.b)>
+DEBUG:  distributed statement: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) distributed_table ON (citus_table_alias.a OPERATOR(pg_catalog.=) distributed_table.a) WHEN MATCHED THEN UPDATE SET b = distributed_table.b WHEN NOT MATCHED THEN INSERT (a, b) VALUES (distributed_table.a, distributed_table.b)
+DEBUG:  Execute MERGE task list
 MERGE INTO schema_shard_table.distributed_table USING nullkey_c1_t1 ON (nullkey_c1_t1.a = schema_shard_table.distributed_table.a)
 WHEN MATCHED THEN DELETE
 WHEN NOT MATCHED THEN INSERT VALUES (nullkey_c1_t1.a, nullkey_c1_t1.b);
@@ -163,7 +180,13 @@ WHEN MATCHED THEN UPDATE SET b = schema_shard_table.reference_table.b;
 DEBUG:  A mix of distributed and reference table, try repartitioning
 DEBUG:  A mix of distributed and reference table, routable query is not possible
 DEBUG:  Creating MERGE repartition plan
-ERROR:  MERGE operation across distributed schemas or with a row-based distributed table is not yet supported
+DEBUG:  Distributed planning for a fast-path router query
+DEBUG:  Creating router plan
+DEBUG:  Collect source query results on coordinator
+DEBUG:  Create a MERGE task list that needs to be routed
+DEBUG:  <Deparsed MERGE query: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) reference_table ON (citus_table_alias.a OPERATOR(pg_catalog.=) reference_table.a) WHEN MATCHED THEN UPDATE SET b = reference_table.b>
+DEBUG:  distributed statement: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) reference_table ON (citus_table_alias.a OPERATOR(pg_catalog.=) reference_table.a) WHEN MATCHED THEN UPDATE SET b = reference_table.b
+DEBUG:  Execute MERGE task list
 MERGE INTO schema_shard_table.reference_table USING nullkey_c1_t1 ON (nullkey_c1_t1.a = schema_shard_table.reference_table.a)
 WHEN MATCHED THEN UPDATE SET b = nullkey_c1_t1.b
 WHEN NOT MATCHED THEN INSERT VALUES (nullkey_c1_t1.a, nullkey_c1_t1.b);
@@ -174,7 +197,13 @@ WHEN MATCHED THEN UPDATE SET b = schema_shard_table.citus_local_table.b;
 DEBUG:  A mix of distributed and local table, try repartitioning
 DEBUG:  A mix of distributed and citus-local table, routable query is not possible
 DEBUG:  Creating MERGE repartition plan
-ERROR:  MERGE operation across distributed schemas or with a row-based distributed table is not yet supported
+DEBUG:  Distributed planning for a fast-path router query
+DEBUG:  Creating router plan
+DEBUG:  Collect source query results on coordinator
+DEBUG:  Create a MERGE task list that needs to be routed
+DEBUG:  <Deparsed MERGE query: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) citus_local_table ON (citus_table_alias.a OPERATOR(pg_catalog.=) citus_local_table.a) WHEN MATCHED THEN UPDATE SET b = citus_local_table.b>
+DEBUG:  distributed statement: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) citus_local_table ON (citus_table_alias.a OPERATOR(pg_catalog.=) citus_local_table.a) WHEN MATCHED THEN UPDATE SET b = citus_local_table.b
+DEBUG:  Execute MERGE task list
 MERGE INTO schema_shard_table.citus_local_table USING nullkey_c1_t1 ON (nullkey_c1_t1.a = schema_shard_table.citus_local_table.a)
 WHEN MATCHED THEN DELETE;
 DEBUG:  A mix of distributed and local table, try repartitioning
@@ -210,7 +239,12 @@ WHEN MATCHED THEN UPDATE SET b = cte.b;
 DEBUG:  Distributed tables are not co-located, try repartitioning
 DEBUG:  For MERGE command, all the distributed tables must be colocated
 DEBUG:  Creating MERGE repartition plan
-ERROR:  MERGE operation across distributed schemas or with a row-based distributed table is not yet supported
+DEBUG:  Router planner cannot handle multi-shard select queries
+DEBUG:  Collect source query results on coordinator
+DEBUG:  Create a MERGE task list that needs to be routed
+DEBUG:  <Deparsed MERGE query: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) cte ON (citus_table_alias.a OPERATOR(pg_catalog.=) cte.a) WHEN MATCHED THEN UPDATE SET b = cte.b>
+DEBUG:  distributed statement: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) cte ON (citus_table_alias.a OPERATOR(pg_catalog.=) cte.a) WHEN MATCHED THEN UPDATE SET b = cte.b
+DEBUG:  Execute MERGE task list
 WITH cte AS materialized (
     SELECT * FROM schema_shard_table.distributed_table
 )
@@ -219,7 +253,12 @@ WHEN MATCHED THEN UPDATE SET b = cte.b;
 DEBUG:  Distributed tables are not co-located, try repartitioning
 DEBUG:  For MERGE command, all the distributed tables must be colocated
 DEBUG:  Creating MERGE repartition plan
-ERROR:  MERGE operation across distributed schemas or with a row-based distributed table is not yet supported
+DEBUG:  Router planner cannot handle multi-shard select queries
+DEBUG:  Collect source query results on coordinator
+DEBUG:  Create a MERGE task list that needs to be routed
+DEBUG:  <Deparsed MERGE query: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) cte ON (citus_table_alias.a OPERATOR(pg_catalog.=) cte.a) WHEN MATCHED THEN UPDATE SET b = cte.b>
+DEBUG:  distributed statement: MERGE INTO schema_shard_table1.nullkey_c1_t1_4005006 citus_table_alias USING (SELECT intermediate_result.a, intermediate_result.b FROM read_intermediate_result('merge_into_XXX_4005006'::text, 'binary'::citus_copy_format) intermediate_result(a integer, b integer)) cte ON (citus_table_alias.a OPERATOR(pg_catalog.=) cte.a) WHEN MATCHED THEN UPDATE SET b = cte.b
+DEBUG:  Execute MERGE task list
 SET client_min_messages TO WARNING;
 DROP SCHEMA schema_shard_table1 CASCADE;
 DROP SCHEMA schema_shard_table2 CASCADE;