[pgpool-hackers: 1307] Re: [pgpool -C option] need more description?

[Tatsuo Ishii]

> Hi Ishii-san,
> 
> Thanks for prompt response,
> 
>> -----Original Message-----
>> From: Tatsuo Ishii [mailto:ishii at postgresql.org]
>> Sent: Wednesday, January 06, 2016 8:31 AM
>> To: Dangminh Huong(ダンＭ フーン) <huo-dangminh at ys.jp.nec.com>;
>> Yanagisawa Hiroshi(柳澤 博) <hir-yanagisawa at ut.jp.nec.com>
>> Cc: pgpool-hackers at pgpool.net
>> Subject: Re: [pgpool-hackers: 1303] Re: [pgpool -C option] need more
>> description?
>> 
>> I appeared that the implementation of -c or --clear-cache is quite
>> confusing. It does exactly the same thing as -C or --clear-oidmaps. So
>> there's no point to have both of options at all.  Moreover -c or
>> --clear-cache is not shown when pgpool --help is requested. Apparently
>> -c or --clear-cache is useless, and I doubt if we need to have this in
>> 3.5.
> 
> I think clear oidmaps should be processed along with clear cache.

No, it's not possible at the moment because pgpool-II cannot
distinguish its own cache entries from other entries registered by
certain applications on the memcached server. If we could assume that
the memcached server is dedicated to pgpool-II, just blowing up all of
the cache entries on the memcached server is enough, but that is too
simple assumption I guess.

> So, remove -C option and add -c option with clear both of oidmaps
> and cache is also a solution in V3.5?
> 
> Best regards,
> ---
> Dang Minh Huong
> NEC Solution Innovators, Ltd.
> http://www.nec-solutioninnovators.co.jp/en/
> 
>> 
>> Best regards,
>> --
>> Tatsuo Ishii
>> SRA OSS, Inc. Japan
>> English: http://www.sraoss.co.jp/index_en.php
>> Japanese:http://www.sraoss.co.jp
>> 
>> >> Hi all,
>> >>
>> >> I think below case is depended on the way of using
>> >> but is it need to be added more detail at pgpool -C option?
>> >> something like "But not clear related cache in memcached server."?
>> >>
>> >> When memcached is using in "In Memory Cached" mode, pgpool
>> >> start with -C option does not clear related cache in cache
>> >> server.
>> >> Obviously it lead to get the old query result by SELECT
>> >> as below.
>> >
>> > Sounds a fair complaint. Will fix.
>> >
>> > Best regards,
>> > --
>> > Tatsuo Ishii
>> > SRA OSS, Inc. Japan
>> > English: http://www.sraoss.co.jp/index_en.php
>> > Japanese:http://www.sraoss.co.jp
>> >
>> >> ===
>> >>
>> >> testdb=# select * from testtbl;   -- create cache
>> >>  id
>> >> ----
>> >>   1
>> >> (1 row)
>> >>
>> >> testdb=# \q
>> >> ]$ pgpool stop
>> >> ]$ pgpool -C -d -n > /var/log/pgpool/log 2>&1 & # start with -C option
>> >> ]$ psql -p 9999
>> >> psql (9.4.4)
>> >> Type "help" for help.
>> >>
>> >> testdb=# insert into testtbl values(1);
>> >> INSERT 0 1
>> >> testdb=# select * from testtbl;  -- old query result from cache server
>> >>  id
>> >> ----
>> >>   1
>> >> (1 row)
>> >>
>> >> ===
>> >>
>> >> Best regards,
>> >> ---
>> >> Dang Minh Huong
>> >> NEC Solution Innovators, Ltd.
>> >> http://www.nec-solutioninnovators.co.jp/en/
>> >>
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>