[Pgpool-hackers] Invalidating relcache

[Yoshiharu Mori]

> Hi,
> 
> Pgpool-II maintaines internal relation cache to caching the query
> result against backend. The cache scope is per session i.e. existing
> in pgpool child process. The cache is mainly used for inquring system
> catalog to know if the table is a tempory one, or rewirting timestamp
> for example. Problem is, if the structure of a table which is in the
> cache is changed by ALTER TABLE ADD COLUMN or some such, the contents
> of the relcache are not valid anymore.

Is it difficult to refresh the cache when the ALTER or some query with 
problem is issued?
(Is it too simple..?)

> 
> The only solution at present is, restarting pgpool or using
> child_life_time, not super conveninet.
> 
> My idea is adding an expiration timer in the cache entry so that the
> cache entry is invalidated after N seconds. The N can be changed by
> editing pgpool.conf.
> 
> Thoughts?
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese: http://www.sraoss.co.jp
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-- 
Yoshiharu Mori <y-mori at sraoss.co.jp>
SRA OSS, Inc Japan http://www.sraoss.co.jp
TEL: 03-5979-2701 
FAX: 03-5979-2702