Re: One long transaction or multiple short transactions?

Sounds like a locking problem, but assuming you aren’t sherlock holmes and simply want to get the thing working as soon as possible:

Stick a fast SSD in there (whether you stay on VM or physical). If you have enough I/O, you may be able to solve the problem with brute force.
SSDs are a lot cheaper than your time.

Suggest you forward this to your operators: a talk I have about optimising multi-threaded work in postgres:

http://graemebell.net/foss4gcomo.pdf (Slides: “Input/Output” in the middle of the talk and also the slides at the end labelled “For Techies")

Graeme Bell

p.s. You mentioned a VM. Consider making the machine physical and not VM. You’ll get a performance boost and remove the risk of DB corruption from untrustworthy VM fsyncs. One day there will be a power cut or O/S crash during these your writes and with a VM you’ve a reasonable chance of nuking your DB because VM virtualised storage often doesn’t honour fsync (for performance reasons), but it’s fundamental to correct operation of PG.

> On 08 Oct 2015, at 01:40, Carlo <reg01(at)stonebanks(dot)ca> wrote:
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> I am told 32 cores on a LINUX VM. The operators have tried limiting the number of threads. They feel that the number of connections is optimal. However, under the same conditions they noticed a sizable boost in performance if the same import was split into two successive imports which had shorter transactions.
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