Add docs for Postgres standalone setup

[mmomjian]

This is a common source of issues with installations. Hoping to start consolidating the commands required in this article to have a place to point people to.

@mertalev appreciate your eyes

[mertalev]

Thanks for working on this! We were actually just talking about making a page for this.

[mmomjian]

Thanks for working on this! We were actually just talking about making a page for this.

Sure thing! I think I made all those updates, lmk what you think.

[mmomjian]

@mertalev just tested this. I don't think the pg_vector_index_stat is created initially. I also tried adding the extension outside of a transaction block, and had the same behavior. We might want to try the ALTER DEFAULT method?

trash1=# BEGIN;
BEGIN
trash1=*# CREATE EXTENSION vectors;
CREATE EXTENSION earthdistance CASCADE;
CREATE EXTENSION
NOTICE:  installing required extension "cube"
CREATE EXTENSION
trash1=*# \d
Did not find any relations.
trash1=*# GRANT SELECT ON TABLE pg_vector_index_stat to postgres;
ERROR:  relation "pg_vector_index_stat" does not exist
trash1=!# COMMIT;
ROLLBACK

[mertalev]

Looks good!

[mertalev]

That's interesting. We can go with ALTER DEFAULT if it isn't created immediately.