From: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
---|---|
To: | Magnus Hagander <mha(at)sollentuna(dot)net> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Mark Kirkwood <markir(at)paradise(dot)net(dot)nz>, Andrew Dunstan <andrew(at)dunslane(dot)net>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: PostgreSQL win32 fragmentation issue |
Date: | 2006-12-03 13:57:08 |
Message-ID: | 20061203135708.GA22386@svana.org |
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Lists: | pgsql-hackers |
On Sun, Dec 03, 2006 at 11:54:05AM +0100, Magnus Hagander wrote:
> Yes, they definitly do. That's why for exapmle SQLServer provides the
> commands "DBCC CHECKCONTIG" and "DBCC INDEXDEFRAG". Along with comments
> like this:
>
> "DBCC SHOWCONTIG determines whether the table is heavily fragmented.
> Table fragmentation occurs through the process of data modifications
> (INSERT, UPDATE, and DELETE statements) made against the table. Because
> these modifications are not ordinarily distributed equally among the
> rows of the table, the fullness of each page can vary over time. For
> queries that scan part or all of a table, such table fragmentation can
> cause additional page reads. This hinders parallel scanning of data."
But that's measuring something else I think. That's not looking at how
the pages are physically mapped on disk, but at how tuples are spread
across pages.. Maybe in sqlserver tuples can span pages?
That's not a kind of fragmentation relevent to postgresql. This is what
the FSM is for.
Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.
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