Re: "NEVER" cautioned to auto_explain's log_analyze parameter on Production

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От Jeff Janes
Тема Re: "NEVER" cautioned to auto_explain's log_analyze parameter on Production
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Msg-id CAMkU=1ync6hzQgJJVZ5B3U2Y=MkZ29oMFBkteTOHbpzTc-G-Tg@mail.gmail.com
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Ответ на "NEVER" cautioned to auto_explain's log_analyze parameter onProduction  (Jacque <jacqueedmund@gmail.com>)
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On Wed, Feb 26, 2020 at 4:17 PM Jacque <jacqueedmund@gmail.com> wrote:
I've seen it said to "NEVER" apply auto_explain's log_analyze parameter
on Production.    I get the general foreboding doom that can be beset by
a highly looping control structure eating up disk space (with no
indication of its exit condition time) but is genrous-disk-writes 
pretty much the only reason for avoiding this in folk's opinion?  

log_analyze doesn't take up dreadful amounts of disk space.  log_min_duration and sample_rate are how you control disk usage.

Some systems (combination of hardware and kernel) have slow clock access, and turning on log_anayze will greatly slow down your CPU-bound queries on such systems (I've seen as much as 10x slower), even the queries that end up not meeting log_min_duration.  If you are running a modern kernel on modern hardware, that probably isn't a problem.  It will still down queries by some amount, but probably not enough to matter, assuming the information it produces is valuable to you.

Cheers,

Jeff

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