Re: Having query cache in core - Mailing list pgsql-hackers

From Tatsuo Ishii
Subject Re: Having query cache in core
Date
Msg-id 20180512.071830.919721368413960369.t-ishii@sraoss.co.jp
Whole thread Raw
In response to Re: Having query cache in core  (CK Tan <cktan@vitessedata.com>)
Responses Re: Having query cache in core  (CK Tan <cktan@vitessedata.com>)
List pgsql-hackers
>> > I think you need to know which tables are involved and if they were
>> > modified.
>>
>> Of course. While creating a cache entry for a SELECT, we need to
>> analyze it and extract tables involved in the SELECT. The information
>> should be stored along with the cache entry. If any of the tables were
>> modified, cache entries using the table must be removed.
>> (these are already implemented in Pgpool-II's in memory query cache)
>>
> 
> How do you handle tables hiding behind views? Also how does cached entries
> in pgpools know if some tables are modified without going thru pgpool, eg
> pgplsql or trigger or via psql directly?

Pgpool-II do not invalidate cache entries for views, triggers and
others. That's an limitation of the implementation in Pgpool-II.

I think in-core query cache would not have the limitation because it
would have a full access to system catalogs and wal.

Best regards,
--
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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