Tradionally our planner works in the following order:
router - > pushdown -> repartition -> pull to coordinator
However, for INSERT .. SELECT commands, we did not support "router".
In practice, that is not a big issue, because pushdown planning can
handle router case as well.
However, with PG 16, certain outer joins are converted to JOIN without
any conditions (e.g., JOIN .. ON (true)) and the filters are pushed down
to the tables.
When the filters are pushed down to the tables, router planner can
detect. However, pushdown planner relies on JOIN conditions.
An example query:
```
INSERT INTO agg_events (user_id)
SELECT raw_events_first.user_id
FROM raw_events_first LEFT JOIN raw_events_second
ON raw_events_first.user_id = raw_events_second.user_id
WHERE raw_events_first.user_id = 10;
```
As a side effect of this change, now we can also relax certain
limitation that "pushdown" planner emposes, but not "router". So, with
this PR, we also allow those.
Closes https://github.com/citusdata/citus/pull/6772
DESCRIPTION: Prevents unnecessarily pulling the data into coordinator
for some INSERT .. SELECT queries that target a single-shard group
Changes test files in multi and multi-1 schedules such that they
accomodate coordinator in metadata.
Changes fall into the following buckets:
1. When coordinator is in metadata, reference table shards are present
in coordinator too.
This changes test outputs checking the table size, shard numbers etc.
for reference tables.
2. When coordinator is in metadata, postgres tables are converted to
citus local tables whenever a foreign key relationship to them is
created. This changes some test cases which tests it should not be
possible to create foreign keys to postgres tables.
3. Remove lines that add/remove coordinator for testing purposes.
Önder Kalacı
Ahmet Gedemenli
Onur Tirtir
Emel Şimşek