DESCRIPTION: Fixes a crash that happens because of unsafe catalog access
when re-assigning the global pid after application_name changes.
When application_name changes, we don't actually need to
try re-assigning the global pid for external client backends because
application_name doesn't affect the global pid for such backends. Plus,
trying to re-assign the global pid for external client backends would
unnecessarily cause performing a catalog access when the cached local
node id is invalidated. However, accessing to the catalog tables is
dangerous in certain situations like when we're not in a transaction
block. And for the other types of backends, i.e., the Citus internal
backends, we need to re-assign the global pid when the application_name
changes because for such backends we simply extract the global pid
inherited from the originating backend from the application_name -that's
specified by originating backend when openning that connection- and this
doesn't require catalog access.
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.
Onur Tirtir
Emel Şimşek
Jelte Fennema
Hadi Moshayedi