[pgpool-hackers: 1617] Re: Redirecting queries to standby as much as possible

[Yugo Nagata]

On Fri, 10 Jun 2016 15:13:19 +0900 (JST)
Tatsuo Ishii <ishii at postgresql.org> wrote:

> Submitter of bug 195 (http://www.pgpool.net/mantisbt/view.php?id=195)
> wants to redirect queries to standby as much as possible if the
> transaction is read only. This brings up interesting conflicts to
> current behavior of pgpool-II:
> 
> - the weight parameters of backend info needs to be ignored if the
>   transaction is read only
> 
> - black and white function list need to be ignored if the transaction
>   is read only
> 
> - database_redirect_preference_list needs to be ignored if the
>   transaction is read only
> 
> - app_name_redirect_preference_list needs to be ignored if the
>   transaction is read only
> 
> After all, if we don't want to confuse existing users in the use cases
> above, we need to invent a new switch to change the redirecting
> behavior depending on whether the transaction is read only or not.

I agree that to add new switch is good because it is simple and preserves
compatibility.

However, even in the current version, the priority of the above rules is
confusing. I think the priority rule should be summarized in the document
explicitly.

> 
> Comments? Opinions?
> --
> 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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-- 
Yugo Nagata <nagata at sraoss.co.jp>