I'm not sure where else to look, so I'm asking here for tips.
I have a table in a remote (Heroku-managed) postgresql database (PG 10.7).
On the other end, (PG 11.3) I have a foreign table configured with a materialized view in front of it.
Up until Thursday evening, it was taking about 12 - 15 seconds to refresh, it is only 15,000 rows with 41 columns. Since Thursday evening it has been taking 15 _minutes_ or more to refresh. Nothing changed on my end that I'm aware of. It completes, it just takes forever.
Here is a summary of what I've tried:
1) Refreshing the materialized views of other tables from that same source database, some much bigger, still perform within seconds as they always have.
2) Dropping the foreign table and the materialized view and recreating them didn't help.
3) It doesn't matter whether I refresh concurrently or not.
4) Configuring the foreign table and materialized view on my laptop's postgresql instance exhibited the same behavior for just this one table.
5) Querying the foreign table directly for a specific row was fast.
6) Reindex and vacuum full analyze on the source table didn't help.
7) Bumping the database on my end to 11.4, didn't help.
8) There are no locks on either database that I can see while the query appears to be stalled.
9) Running the materialized view select directly against the source table completes within seconds.
10) Running the materialized view select directly against the foreign table also completes within a few seconds.
11) Dropping all of the indexes on the materialized view, including the unique one and running the refresh (without 'concurrently') does not help.
I feel like I'm missing something obvious here, but I'm just not seeing it. Any thoughts about where else to look?