Re: Slow count(*) again...

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От Jesper Krogh
Тема Re: Slow count(*) again...
Дата
Msg-id 4CC082C4.4070704@krogh.cc
обсуждение исходный текст
Ответ на Re: Slow count(*) again...  (Scott Carey <scott@richrelevance.com>)
Ответы Re: Slow count(*) again...  (Scott Carey <scott@richrelevance.com>)
Список pgsql-performance
On 2010-10-21 06:47, Scott Carey wrote:
> On a wimpy disk, I/O bound for sure.   But my disks go 1000MB/sec.
> No query can go fast enough for them.  The best I've gotten is
> 800MB/sec, on a wide row (average 800 bytes).  Most tables go
> 300MB/sec or so.  And with 72GB of RAM, many scans are in-memory
> anyway.

Is it cpu or io bound while doing it?
Can you scan it faster using time cat relation-oid.* > /dev/null

> A single SSD with supercapacitor will go about 500MB/sec by itself
> next spring.   I will easily be able to build a system with 2GB/sec
> I/O for under $10k.

What filesystem are you using? Readahead?
Can you try to check the filesystemfragmentation of the table using filefrag?

-- 
Jesper



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