PG17 compatibility: Fix Test Failure in local_table_join (#7732)

PostgreSQL 17 seems to have introduced improvements in how correlated
subqueries are handled during plan generation. Instead of generating a
trivial subplan with WHERE true, it now applies more specific filtering
(WHERE (key = 5)), which makes the execution plan more efficient.

postgres/postgres@b262ad44


```
diff -dU10 -w /__w/citus/citus/src/test/regress/expected/local_table_join.out /__w/citus/citus/src/test/regress/results/local_table_join.out
--- /__w/citus/citus/src/test/regress/expected/local_table_join.out.modified	2024-11-05 09:53:50.423970699 +0000
+++ /__w/citus/citus/src/test/regress/results/local_table_join.out.modified	2024-11-05 09:53:50.463971296 +0000
@@ -1420,32 +1420,32 @@
   ) as subq_1
 ) as subq_2;
 DEBUG:  Wrapping relation "custom_pg_type" to a subquery
 DEBUG:  generating subplan 204_1 for subquery SELECT typdefault FROM local_table_join.custom_pg_type WHERE true
 ERROR:  direct joins between distributed and local tables are not supported
 HINT:  Use CTE's or subqueries to select from local tables and use them in joins
 -- correlated sublinks are not yet supported because of #4470, unless we convert not-correlated table
 SELECT COUNT(*) FROM distributed_table d1 JOIN postgres_table using(key)
 WHERE d1.key IN (SELECT key FROM distributed_table WHERE d1.key = key and key = 5);
 DEBUG:  Wrapping relation "postgres_table" to a subquery
-DEBUG:  generating subplan XXX_1 for subquery SELECT key FROM local_table_join.postgres_table WHERE true
+DEBUG:  generating subplan 206_1 for subquery SELECT key FROM local_table_join.postgres_table WHERE (key OPERATOR(pg_catalog.=) 5)
```

Co-authored-by: Naisila Puka <37271756+naisila@users.noreply.github.com>

src/test/regress/expected/local_table_join.out

@@ -1425,21 +1425,21 @@ ERROR:  direct joins between distributed and local tables are not supported
 HINT:  Use CTE's or subqueries to select from local tables and use them in joins
 -- correlated sublinks are not yet supported because of #4470, unless we convert not-correlated table
 SELECT COUNT(*) FROM distributed_table d1 JOIN postgres_table using(key)
-WHERE d1.key IN (SELECT key FROM distributed_table WHERE d1.key = key and key = 5);
+WHERE d1.key IN (SELECT key FROM distributed_table WHERE d1.key = key);
 DEBUG:  Wrapping relation "postgres_table" to a subquery
 DEBUG:  generating subplan XXX_1 for subquery SELECT key FROM local_table_join.postgres_table WHERE true
-DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (local_table_join.distributed_table d1 JOIN (SELECT postgres_table_1.key, NULL::text AS value, NULL::jsonb AS value_2 FROM (SELECT intermediate_result.key FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer)) postgres_table_1) postgres_table USING (key)) WHERE (d1.key OPERATOR(pg_catalog.=) ANY (SELECT distributed_table.key FROM local_table_join.distributed_table WHERE ((d1.key OPERATOR(pg_catalog.=) distributed_table.key) AND (distributed_table.key OPERATOR(pg_catalog.=) 5))))
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count FROM (local_table_join.distributed_table d1 JOIN (SELECT postgres_table_1.key, NULL::text AS value, NULL::jsonb AS value_2 FROM (SELECT intermediate_result.key FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer)) postgres_table_1) postgres_table USING (key)) WHERE (d1.key OPERATOR(pg_catalog.=) ANY (SELECT distributed_table.key FROM local_table_join.distributed_table WHERE (d1.key OPERATOR(pg_catalog.=) distributed_table.key)))
  count
 ---------------------------------------------------------------------
    100
 (1 row)
 
 set citus.local_table_join_policy to 'prefer-distributed';
 SELECT COUNT(*) FROM distributed_table d1 JOIN postgres_table using(key)
-WHERE d1.key IN (SELECT key FROM distributed_table WHERE d1.key = key and key = 5);
+WHERE d1.key IN (SELECT key FROM distributed_table WHERE d1.key = key);
 DEBUG:  Wrapping relation "distributed_table" "d1" to a subquery
 DEBUG:  generating subplan XXX_1 for subquery SELECT key FROM local_table_join.distributed_table d1 WHERE true
-DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count FROM ((SELECT d1_1.key, NULL::text AS value, NULL::jsonb AS value_2 FROM (SELECT intermediate_result.key FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer)) d1_1) d1 JOIN local_table_join.postgres_table USING (key)) WHERE (d1.key OPERATOR(pg_catalog.=) ANY (SELECT distributed_table.key FROM local_table_join.distributed_table WHERE ((d1.key OPERATOR(pg_catalog.=) distributed_table.key) AND (distributed_table.key OPERATOR(pg_catalog.=) 5))))
+DEBUG:  Plan XXX query after replacing subqueries and CTEs: SELECT count(*) AS count FROM ((SELECT d1_1.key, NULL::text AS value, NULL::jsonb AS value_2 FROM (SELECT intermediate_result.key FROM read_intermediate_result('XXX_1'::text, 'binary'::citus_copy_format) intermediate_result(key integer)) d1_1) d1 JOIN local_table_join.postgres_table USING (key)) WHERE (d1.key OPERATOR(pg_catalog.=) ANY (SELECT distributed_table.key FROM local_table_join.distributed_table WHERE (d1.key OPERATOR(pg_catalog.=) distributed_table.key)))
 ERROR:  direct joins between distributed and local tables are not supported
 HINT:  Use CTE's or subqueries to select from local tables and use them in joins
 set citus.local_table_join_policy to 'auto';