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/
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