[pgpool-hackers: 1789] Re: Problem with locking in In Memory Cache

[Tatsuo Ishii]

Thank you for the report. I will look into this.

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp

> Hi, 
> 
> I have found a problem with table locking In In Memory Cache feature.
> Confirmed in pgpool-II 3.4.8 in both memcached and sharedmemory mode.
> 
> When using JDBC to access to pgpool-II. In the second time of (the same) query 
> executing, it returned result from cached, but after that pg_stat_activity's state of query 
> was still in 'active' and not change. 
> So the locks made by executed query was not release too.
> 
> Take a look at source and i found that, in extended protocol, locking of table 
> was made when 'P'(Parse) message is sent, and release when 'S'(Sync) message
> is sent to backend.
> But when memory_cache_enabled is true. Parse message is sent but Sync message 
> is not sent to backend.
> In pool_fetch_from_memory_cache function. It sound that when cache found, 
> Sync message from frontend was discard but not forward to backend to finish query.
> I think, it is necessary to tell to backend to finish executed query here, is that right?
> 
> Best regards,
> ---
> Dang Minh Huong
> NEC Solution Innovators, Ltd.
> http://www.nec-solutioninnovators.co.jp/en/
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