Re: Reducing relcache memory usage 2: shrink sizeof(RelationData)

Hi Yilin,

> There is still a crash in the v5 patch series, similar to the predicate
> crash that Haibo already mentioned.
> Minimal reproduction steps:
>
> CREATE TABLE t(a int primary key, b text);
> CREATE INDEX t_b_idx ON t(b);
>
> SELECT pg_relation_is_updatable('t_b_idx'::regclass, false);
> -- server closed the connection unexpectedly
>
> SELECT pg_column_is_updatable('t_b_idx'::regclass, 1::int2, false);
> -- server closed the connection unexpectedly
>
> Please take this into consideration.
Thanks for testing the patch!

The problem was that relation_is_updatable() accessed rel->rd_rules
without checking that the relcache entry is actually for a relation and
not for an index. Bailing for indexes fixes the crash:

/* Indexes are not updatable */
if (RelationIsIndex(rel))
{
relation_close(rel, AccessShareLock);
return 0;
}

Attached is patch set v6 with the fix.

--
David Geier