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Re: Disk buffering of resultsets - Mailing list pgsql-jdbc

From Lussier, Denis
Subject Re: Disk buffering of resultsets
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Msg-id CAHKhnVX5qxNOCBFXwivt1Mwzdaru9hoG9wCviAKUj9Dcmnu=0w@mail.gmail.com
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In response to Re: Disk buffering of resultsets  (John R Pierce <pierce@hogranch.com>)
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I agree that this possible new feature would definitely be off by default.

I like Craig's idea to use the jdk7 temp file handling.   I propose to this project keep it simple (at least at first) and start with this as a jdbc41 only feature.

Many people use pgjdbc for OLTP style transactions and wouldn't ever want to spill to disk.   This is why (IMHO) the algorithm that determines under which stress
condition this feature uses (assuming it is enabled) is so critical.

    

On Mon, Sep 22, 2014 at 1:42 PM, John R Pierce <pierce@hogranch.com> wrote:
On 9/22/2014 10:16 AM, Steven Schlansker wrote:
Additionally, if this does get implemented, please leave it off by default.  We
have many SSDs backing our database server and very little space / IOPS on
application nodes (intentionally, and I’m not sure we are the only ones) so
suddenly spilling to disk could be disastrous for our performance.

 we have a high volume messaging subsystem that normally uses no disk, but if a subscriber goes offline, it spools to disk, then when the subscriber comes back, it plays back those spools.  its designed this way, its advertised as working this way, we require high performance dedicated RAID storage on the messaging box for these spools.... time and time again operations has seen it happily hum along for 6 months with no disk IO usage, and push it onto 2nd/3rd tier storage to free up the 1st tier for something else.   then a subscriber goes offline for 14 hours, and the system just croaks and can't keep up.



--
john r pierce                                      37N 122W
somewhere on the middle of the left coast




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