Re: Question about syscache

Peter Eisentraut <peter_e@gmx.net> writes:
> In syscache.c, the structure cachedesc contains a field reloidattr that is
> supposed to contain the number of an attribute that is an OID reference to
> another table.  But what if there are two such attributes?

Specifically, it is a reference to pg_class.

> The concrete case is an index on pg_cast (castsource, casttarget), which
> both reference pg_type.

That is not a reference to pg_class, so you should not make reloidattr
reference it.

The point of reloidattr is that during a relation cache clear event,
it allows catcache to find all catcache rows that are related to that
relation cache entry (eg, pg_attribute, pg_trigger, etc).  So far
there's not been need for more than one such attribute per tuple.
        regards, tom lane