Not skip relation in conversion if it doesn't have RelationRestriction (#4685)

We would exclude tables without relationRestriction from conversion
candidates in local-distributed table joins. This could leave a leftover
local table which should have been converted to a subquery.

Ideally I would expect that in each call to CreateDistributedPlan we
would pass a new plan id, but that seems like a bigger change.

src/backend/distributed/planner/local_distributed_join_planner.c

@@ -384,8 +384,15 @@ static bool
 HasConstantFilterOnUniqueColumn(RangeTblEntry *rangeTableEntry,
 								RelationRestriction *relationRestriction)
 {
-	if (rangeTableEntry == NULL)
+	if (rangeTableEntry == NULL || relationRestriction == NULL)
 	{
+		/*
+		 * Postgres might not pass relationRestriction info with hooks if
+		 * the table doesn't contribute to the result, and in that case
+		 * relationRestriction will be NULL. Ideally it doesn't make sense
+		 * to recursively plan such tables but for the time being we don't
+		 * add any special logic for these tables as it might introduce bugs.
+		 */
 		return false;
 	}
 	List *baseRestrictionList = relationRestriction->relOptInfo->baserestrictinfo;
@@ -538,11 +545,6 @@ CreateConversionCandidates(PlannerRestrictionContext *plannerRestrictionContext,
 
 		RelationRestriction *relationRestriction =
 			RelationRestrictionForRelation(rangeTableEntry, plannerRestrictionContext);
-		if (relationRestriction == NULL)
-		{
-			continue;
-		}
-
 
 		RangeTableEntryDetails *rangeTableEntryDetails =
 			palloc0(sizeof(RangeTableEntryDetails));

src/test/regress/expected/local_dist_join_mixed.out

@@ -1182,9 +1182,9 @@ DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS c
 
 -- w count(*) it works fine as PG ignores the  inner tables
 SELECT count(*) FROM distributed LEFT JOIN local USING (id);
-DEBUG:  Wrapping relation "distributed" to a subquery
-DEBUG:  generating subplan XXX_1 for subquery SELECT id FROM local_dist_join_mixed.distributed WHERE true
-DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count FROM ((SELECT NULL::integer AS "dummy-1", distributed_1.id, NULL::text AS name, NULL::timestamp with time zone AS created_at FROM (SELECT intermediate_result.id FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(id bigint)) distributed_1) distributed LEFT JOIN local_dist_join_mixed.local USING (id))
+DEBUG:  Wrapping relation "local" to a subquery
+DEBUG:  generating subplan XXX_1 for subquery SELECT NULL::integer AS "dummy-1" FROM local_dist_join_mixed.local WHERE true
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (local_dist_join_mixed.distributed LEFT JOIN (SELECT NULL::integer AS "dummy-1", NULL::bigint AS id, NULL::integer AS "dummy-3", NULL::text AS title, NULL::integer AS "dummy-5" FROM (SELECT intermediate_result."dummy-1" FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result("dummy-1" integer)) local_1) local USING (id))
  count
 ---------------------------------------------------------------------
    101
@@ -1200,9 +1200,10 @@ DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS c
 (1 row)
 
 SELECT id, name FROM distributed LEFT JOIN local USING (id) ORDER BY 1 LIMIT 1;
-DEBUG:  Wrapping relation "distributed" to a subquery
-DEBUG:  generating subplan XXX_1 for subquery SELECT id, name FROM local_dist_join_mixed.distributed WHERE true
-DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT distributed.id, distributed.name FROM ((SELECT NULL::integer AS "dummy-1", distributed_1.id, distributed_1.name, NULL::timestamp with time zone AS created_at FROM (SELECT intermediate_result.id, intermediate_result.name FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(id bigint, name text)) distributed_1) distributed LEFT JOIN local_dist_join_mixed.local USING (id)) ORDER BY distributed.id LIMIT 1
+DEBUG:  Wrapping relation "local" to a subquery
+DEBUG:  generating subplan XXX_1 for subquery SELECT NULL::integer AS "dummy-1" FROM local_dist_join_mixed.local WHERE true
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT distributed.id, distributed.name FROM (local_dist_join_mixed.distributed LEFT JOIN (SELECT NULL::integer AS "dummy-1", NULL::bigint AS id, NULL::integer AS "dummy-3", NULL::text AS title, NULL::integer AS "dummy-5" FROM (SELECT intermediate_result."dummy-1" FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result("dummy-1" integer)) local_1) local USING (id)) ORDER BY distributed.id LIMIT 1
+DEBUG:  push down of limit count: 1
  id | name
 ---------------------------------------------------------------------
   0 | 0

src/test/regress/expected/local_table_join.out

@@ -1466,7 +1466,48 @@ DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS c
    100
 (1 row)
 
+-- issue 4682
+create table tbl1 (a int, b int, c int, d int);
+INSERT INTO tbl1 SELECT i,i,i,i FROM generate_series(1,10) i;
+create table custom_pg_operator(oprname text);
+INSERT INTO custom_pg_operator values('a');
+-- try with local tables to make sure the results are same when tbl1 is distributed
+select COUNT(*) from
+  custom_pg_operator
+  inner join tbl1 on (select 1 from custom_pg_type) >= d
+  left join pg_dist_rebalance_strategy on 'by_shard_count' = name
+where a + b + c > 0;
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+select create_distributed_table('tbl1', 'a');
+NOTICE:  Copying data from local table...
+DEBUG:  Copied 10 rows
+NOTICE:  copying the data has completed
+DETAIL:  The local data in the table is no longer visible, but is still on disk.
+HINT:  To remove the local data, run: SELECT truncate_local_data_after_distributing_table($$local_table_join.tbl1$$)
+ create_distributed_table
+---------------------------------------------------------------------
+
+(1 row)
+
+-- there is a different output in pg11 and in this query the debug messages are not
+-- as important as the others so we use notice
+set client_min_messages to NOTICE;
+select COUNT(*) from
+  custom_pg_operator
+  inner join tbl1 on (select 1 from custom_pg_type) >= d
+  left join pg_dist_rebalance_strategy on 'by_shard_count' = name
+where a + b + c > 0;
+ count
+---------------------------------------------------------------------
+     1
+(1 row)
+
+SET client_min_messages to DEBUG1;
 RESET client_min_messages;
 \set VERBOSITY terse
 DROP SCHEMA local_table_join CASCADE;
-NOTICE:  drop cascades to 18 other objects
+NOTICE:  drop cascades to 20 other objects

src/test/regress/sql/local_table_join.sql

@@ -413,6 +413,33 @@ WHERE distributed_table_pkey.key IN (SELECT key FROM distributed_table_pkey WHER
 SELECT COUNT(*) FROM distributed_table_pkey JOIN postgres_table using(key)
 WHERE distributed_table_pkey.key IN (SELECT key FROM distributed_table_pkey WHERE key = 5) AND distributed_table_pkey.key = 5;
 
+-- issue 4682
+create table tbl1 (a int, b int, c int, d int);
+INSERT INTO tbl1 SELECT i,i,i,i FROM generate_series(1,10) i;
+
+create table custom_pg_operator(oprname text);
+INSERT INTO custom_pg_operator values('a');
+
+-- try with local tables to make sure the results are same when tbl1 is distributed
+select COUNT(*) from
+  custom_pg_operator
+  inner join tbl1 on (select 1 from custom_pg_type) >= d
+  left join pg_dist_rebalance_strategy on 'by_shard_count' = name
+where a + b + c > 0;
+
+select create_distributed_table('tbl1', 'a');
+
+-- there is a different output in pg11 and in this query the debug messages are not
+-- as important as the others so we use notice
+set client_min_messages to NOTICE;
+select COUNT(*) from
+  custom_pg_operator
+  inner join tbl1 on (select 1 from custom_pg_type) >= d
+  left join pg_dist_rebalance_strategy on 'by_shard_count' = name
+where a + b + c > 0;
+SET client_min_messages to DEBUG1;
+
+
 RESET client_min_messages;
 \set VERBOSITY terse
 DROP SCHEMA local_table_join CASCADE;