Clarification on Role Access Rights to Table Indexes

["David G. Johnston" <david.g.johnston@xxxxxxxxx>]

On Monday, February 17, 2025, Ayush Vatsa <ayushvatsa1810@xxxxxxxxx> wrote:

postgres=# CREATE ROLE alpha;

CREATE ROLE
postgres=# GRANT SELECT ON pg_class TO alpha;

This is pointless, everyone (i.e. the PUBLIC pseudo-role) can already read pg_class.

1. Can a role have access rights to a table without having access to its index?

Roles don’t directly interact with indexes in PostgreSQL so this doesn’t even make sense.  But if you need a yes/no answer, then yes. 

3. If no, and the role inherently gets access to the index when granted access to the table, why
does the pg_prewarm call fail [1] in the above scenario?

[1] https://github.com/postgres/postgres/blob/master/contrib/pg_prewarm/pg_prewarm.c#L108-L110

It fails because AFAICS there is no way for it to work on an index, only tables.

David J.

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