pglz performance

From: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>
To: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Cc: Vladimir Leskov <vladimirlesk(at)yandex-team(dot)ru>
Subject: pglz performance
Date: 2019-05-13 02:45:59
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Hi hackers!

I was reviewing Paul Ramsey's TOAST patch[0] and noticed that there is a big room for improvement in performance of pglz compression and decompression.

With Vladimir we started to investigate ways to boost byte copying and eventually created test suit[1] to investigate performance of compression and decompression.
This is and extension with single function test_pglz() which performs tests for different:
1. Data payloads
2. Compression implementations
3. Decompression implementations

Currently we test mostly decompression improvements against two WALs and one data file taken from pgbench-generated database. Any suggestion on more relevant data payloads are very welcome.
My laptop tests show that our decompression implementation [2] can be from 15% to 50% faster.
Also I've noted that compression is extremely slow, ~30 times slower than decompression. I believe we can do something about it.

We focus only on boosting existing codec without any considerations of other compression algorithms.

Any comments are much appreciated.

Most important questions are:
1. What are relevant data sets?
2. What are relevant CPUs? I have only XEON-based servers and few laptops\desktops with intel CPUs
3. If compression is 30 times slower, should we better focus on compression instead of decompression?

Best regards, Andrey Borodin.



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