What select statement can I use to determine 1) the roles that a user belongs to and 2) the tables that a user has access to using PostgreSQL? -

using psql, \dg , \du tells me roles each user (role) belongs to. want determine programmatically single user cannot find system tables used generate results returned \dg.
need special privileges execute query?

as related question, want determine tables role can update.
i've read documentation on create role , grant , surrounding documentation tell me how set roles , privileges, not how test role membership or table access privileges.

there built-in system information functions both. see pg_has_role, etc.

you can query the information_schema role membership data, in particular information_schema.applicable_roles, information_schema.enabled_roles , information_schema.administrable_role_authorizations.

finally, psql \d command can find out psql doing information running psql -e option print sql runs. don't recommend using psql's sql when there's builtin function or information_schema view same information though. psql's approach may faster it's more postgresql-version-specific , may not work postgresql versions other 1 you're running. in case of \du , \dg psql querying pg_catalog.pg_roles part of join against other tables. it's simpler , more portable use information_schema views instead.

this should the documentation entries on role membership; i'll post patch adds appropriate cross-references.