Re: Performance on Bulk Insert to Partitioned Table

From: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
To: Charles Gomes <charlesrg(at)outlook(dot)com>
Cc: Ondrej Ivanič <ondrej(dot)ivanic(at)gmail(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Performance on Bulk Insert to Partitioned Table
Date: 2012-12-23 22:55:16
Message-ID: CAMkU=1xbdrp-HsPQ5kJZDxDTWa8NnvLiYB9kXiCYN8X9WSGv8Q@mail.gmail.com
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On Thursday, December 20, 2012, Charles Gomes wrote:

> True, that's the same I feel, I will be looking to translate the trigger
> to C if I can find good examples, that should accelerate.
>

I think your performance bottleneck is almost certainly the dynamic SQL.
Using C to generate that dynamic SQL isn't going to help much, because it
is still the SQL engine that has to parse, plan, and execute it.

Are the vast majority if your inserts done on any given day for records
from that same day or the one before; or are they evenly spread over the
preceding year? If the former, you could use static SQL in IF and ELSIF
for those days, and fall back on the dynamic SQL for the exceptions in the
ELSE block. Of course that means you have to update the trigger every day.

> Using rules would be totally bad as I'm partitioning daily and after one
> year having 365 lines of IF won't be fun to maintain.
>

Maintaining 365 lines of IF is what Perl was invented for. That goes for
triggers w/ static SQL as well as for rules.

If you do the static SQL in a trigger and the dates of the records are
evenly scattered over the preceding year, make sure your IFs are nested
like a binary search, not a linear search. And if they are mostly for
"today's" date, then make sure you search backwards.

Cheers,

Jeff

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