From: | Andrey Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru> |
---|---|
To: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com> |
Cc: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, a(dot)lubennikova(at)postgrespro(dot)ru, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Reduce amount of WAL generated by CREATE INDEX for gist, gin and sp-gist |
Date: | 2018-12-18 05:41:48 |
Message-ID: | 1cdb9c52-e8fb-124b-3949-d3be8a6a7451@postgrespro.ru |
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Lists: | pgsql-hackers |
On 30.11.2018 15:10, Dmitry Dolgov wrote:
> Thank you. I played a bit with this patch, and can confirm visible WAL size
> reduction (it's rather obvious, but still). Although, probably due to lack of
> my knowledge here, I wonder how does it work when an index is build
> concurrently?
Routine generate_xlog_for_rel() works only at phase 2 of concurrent
index building.
At the phase 3, during validate_index() execution we use aminsert() ->
PlaceToPage() mechanism as before the patch.
In the concurrent mode, I do not expect any problems, caused by the patch.
>
>> Benchmarks:
>> -----------
>>
>> Test: pgbench -f gin-WAL-test.sql -t 5:
>> ---------------------------------------
>> master:
>> Latency average: 27696.299 ms
>> WAL size: 2.66 GB
>
> Does it makes sense to measure latency of the entire script, since it contains
> also some preparation work? Of course it still shows the difference between
> patched version and master, but probably in a more noisy way.
Ok. It is used only for demonstration.
--
Andrey Lepikhov
Postgres Professional
https://postgrespro.com
The Russian Postgres Company
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