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Re: Abnormal performance difference between Postgres and MySQL

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Farhan Husain <russoue(at)gmail(dot)com>
Cc: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Abnormal performance difference between Postgres and MySQL
Date: 2009-02-25 21:40:19
Message-ID: 603c8f070902251340i539b249ds1e2949a9822845af@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
>> > shared_buffers = 32MB                   # min 128kB or
>> > max_connections*16kB
>>
>> That's REALLY small for pgsql.  Assuming your machine has at least 1G
>> of ram, I'd set it to 128M to 256M as a minimum.
>
> As I wrote in a previous email, I had the value set to 1792MB (the highest I
> could set) and had the same execution time. This value is not helping me to
> bring down the execution time.

No, you increased work_mem, not shared_buffers.  You might want to go
and read the documentation:

http://www.postgresql.org/docs/current/interactive/runtime-config-resource.html

But at any rate, the large work_mem was producing a very strange plan.
 It may help to see what the system does without that setting.  But
changing shared_buffers will not change the plan, so let's not worry
about that right now.

...Robert

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Subject: Re: Abnormal performance difference between Postgres and MySQL
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