[Pgpool-hackers] Invalidating relcache

[Tatsuo Ishii]

>> 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.
>> 
>> 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?
> 
> Seems interesting. 0 would mean no timer I guess?

Yes, that would be appropreate and mybe the default value for backward
compatibility sake?
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
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