PG17 compatibility: fix multi-1 diffs caused by PG17 optimizer enhancements

[colm-mchugh]

This fix ensures that the expected DEBUG error messages from the router planner in multi_router_planner, multi_router_planner_fast_path and query_single_shard_table are present with PG17.

In query_single_shard_table the diff:

SELECT COUNT(*) FROM citus_local_table t1
 WHERE t1.b IN (
     SELECT b+1 FROM nullkey_c1_t1 t2 WHERE t2.b = t1.a
 );
-DEBUG:  router planner does not support queries that reference non-colocated distributed tables
+DEBUG:  Local tables cannot be used in distributed queries.

occurred because of this PG17 commit which enables the optimizer to pull up a correlated ANY subquery to a join. The fix inhibits subquery pull up by including a volatile function in the predicate involving the ANY subquery, preserving the pre-PG17 optimizer treatment of the query.

In the case of multi_router_planner and multi_router_planner_fast_path the diffs:

-- partition_column is null clause does not prune out any shards,
 -- all shards remain after shard pruning, not router plannable
 SELECT *
 	FROM articles_hash a
 	WHERE a.author_id is null;
-DEBUG:  Router planner cannot handle multi-shard select queries
+DEBUG:  Creating router plan

are because of this PG17 commit, which enables the optimizer to detect and remove redundant IS (NOT) NULL expressions. The fix is to adjust the table definition so the column used for distribution is not marked NOT NULL, thus preserving the pre-PG17 query planning behavior.

Finallly, the DEBUG logging level is lowered for CREATE MATERIALIZED VIEW AS statements in multi_router_planner and multi_router_planner_fast_path because of this PG17 commit; when creating materialized views, use REFRESH logic to load data, a consequence of which is that with client_min_messages at DEBUG2 Postgres emits extra detail for CREATE MATERIALIZED VIEW AS statements.

CREATE MATERIALIZED VIEW mv_articles_hash_empty AS
 	SELECT * FROM articles_hash WHERE author_id = 1;
 DEBUG:  Creating router plan
 DEBUG:  query has a single distribution column value: 1
+DEBUG:  drop auto-cascades to type multi_router_planner.pg_temp_61391
+DEBUG:  drop auto-cascades to type multi_router_planner.pg_temp_61391[]

Note: the number part can vary. This is because of the REFRESH logic added by the aforementioned commit. Also relevant is this PG17 commit which sets the search_path to 'pg_catalog, pg_temp' during maintenance operations (including REFRESH MATERIALIZED VIEW)

[codecov]

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[naisila]

Really good analysis in the PR description, thanks!

[naisila]

This debug is actually useful to see.

Also, we see the extra pg_temp debugs in 3 tests:
multi_router_planner, multi_mx_router_planner, multi_router_planner_fast_path
I think we qualify for a normalize rule here :) Something like:
/DEBUG: drop auto-cascades to type(.*)pg_temp_(.*)/d

[colm-mchugh]

Fair enough.. this would delete lines matching the PG17 DEBUG message from all .out files, right?

Thanks for the suggestion! Agreed that its good to preserve the existing DEBUG messages.

[naisila]

this would delete lines matching the PG17 DEBUG message from all .out files

Hopefully yes