On 22.06.18 00:35, PG Doc comments form wrote: > because 0::OID does not reference a valid pg_collation.oid. > > In the IRC, Zr40 helpfully pointed out that the latest documentation readily > clarifies: "For each column in the index key, this contains the OID of the > collation to use for the index, or zero if the column is not of a collatable > data type."
It's a standard convention in the PostgreSQL system catalogs that OID zero means "none". There are likely many places where this is not explicitly documented. -- Peter Eisentraut http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
