Re: Ideas about a better API for postgres_fdw remote estimates

On 8/29/20 9:50 PM, Tom Lane wrote:
> Years ago (when I was still at Salesforce, IIRC, so ~5 years) we had
> some discussions about making it possible for pg_dump and/or pg_upgrade
> to propagate stats data forward to the new database. There is at least
> one POC patch in the archives for doing that by dumping the stats data
> wrapped in a function call, where the target database's version of the
> function would be responsible for adapting the data if necessary, or
> maybe just discarding it if it couldn't adapt. We seem to have lost
> interest but it still seems like something worth pursuing. I'd guess
> that if such infrastructure existed it could be helpful for this.

Thanks for this helpful feedback.

I found several threads related to the problem [1-3].
I agreed that this task needs to implement an API for
serialization/deserialization of statistics:
pg_load_relation_statistics(json_string text);
pg_get_relation_statistics(relname text);
We can use a version number for resolving conflicts with different
statistics implementations.
"Load" function will validate the values[] anyarray while deserializing
the input json string to the datatype of the relation column.

Maybe I didn't feel all the problems of this task?

1. https://www.postgresql.org/message-id/flat/724322880.K8vzik8zPz%40abook
2.
https://www.postgresql.org/message-id/flat/CAAZKuFaWdLkK8eozSAooZBets9y_mfo2HS6urPAKXEPbd-JLCA%40mail.gmail.com
3.
https://www.postgresql.org/message-id/flat/GNELIHDDFBOCMGBFGEFOOEOPCBAA.chriskl%40familyhealth.com.au

--
regards,
Andrey Lepikhov
Postgres Professional