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Re: PRAGMA page_size;

From: Julian Foad <julianfoad_at_btopenworld.com>
Date: Thu, 16 Feb 2012 10:38:30 +0000 (GMT)

Daniel Shahafwrote:
> Apparently changing the PAGE_SIZE pragma has a significant effect on the
> wc speed:
>
> 65536 [...] 29 s
>  4096 [...] 20 s
>  1024 [...] 19 / 16 s

>
> Now, obviously just using the 65k (the maximum) for the pragma isn't
> always a good idea; but should we make this configurable?  I imagine
> that using, say, 4KB in some setups could have a noticeable difference.

Hi Daniel.  On my (Ubuntu / ext3) system, wc.db gets a default page size of 1024, and if that's the same for you then you're confirming that the default is good.  Have you found systems where the default is a poor choice?

This thread seems to have a useful discussion: <https://bugzilla.mozilla.org/show_bug.cgi?id=416330#c3>, which seems to be saying that a larger default seemed to be helpful for Mozilla on Windows.

It seems from what I read online
that SQLite currently chooses a default of 1024 on many/most systems, and larger on some
systems such as VFS where it can determine that the file system has a larger sector size.  This SQLite enhancement request is relevant:
<http://www.sqlite.org/src/tktview/ba7fdb568d6c80b90dfdc66d44e8a6f29a9ebd0f>, "Page size should auto default to file system block size".

- Julian
Received on 2012-02-16 11:39:06 CET

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