Re: Updates of SE-PostgreSQL 8.4devel patches (r1324)

KaiGai Kohei wrote:

>> Can we support two data types, one for read-only and another for
>> possible creation?  That is not going to work for a query like
>>
>>     SELECT * FROM x WHERE col != 'valid_but_new_security_label'::regseclabel;
>>
>> because the cast would fail if the pg_security row doesn't exist, but
>> the query itself perhaps might succeed and return rows.
>
> It has a same matter. If user cast a text into the type of possible
> creation, it can cause an unnecessary insertion.

How's this for an idea.  Keep a cache in memory, which has a reference
counter.  This counter would only be incremented for written tuples.  At
transaction end (or when the cache is full and you need more room),
entries are evicted; if the reference count is greater than zero on
eviction, a pg_security entry is created.  Otherwise it is just
discarded.  pg_security entry creation (i.e. eviction from cache, or at
transaction end) is WAL-logged, which is enough in case of a crash,
because if a tuple is written with an unlogged pg_security OID, the
transaction did not abort and thus nobody can possibly be interested in
translating it.

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support