in reply to Re: Re: It's bad manners to slurp
in thread It's bad manners to slurp

Contend all you want, as far as I know it's the truth for at least DBD::mysql and DBD::Pg. I imagine it would be fairly easy to test this theory with a properly giant DB and GTop.

-sam

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Re: Re: Re: Re: It's bad manners to slurp
by tantarbobus (Hermit) on Apr 29, 2004 at 16:50 UTC
    It is possible to change this behaviour with both DBD::mysql and DBD::pg For DBD::mysql you can give prepare {mysql_use_result => 1}. But be aware that by doing this, you change the behaviour of the rows() method. And for DBD::pg you can use cursors: 
    
    $db->do("declare imprecator CURSOR FOR select * from test");
    $c = $db->prepare("FETCH 100 FROM imprecator")

    for (1..10) {   # I have a more robust example somewhere
        $c->execute();
        print Data::Dumper::Dumper($c->fetchall_arrayref())
    }

    [download]
    It would probably be possible to encode this in the driver so you could pass an attribute to prepare {pg_use_cursor =>1}.
[reply]
[d/l]
      Another way for simple queries with MySQL 4.x is to use the HANDLER statement. 
      HANDLER table OPEN;
HANDLER table READ FIRST;
HANDLER table READ NEXT;

      [download]
[reply]
[d/l]
        Care to elaborate? I'm unfamiliar with HANDLER.

        -sam

[reply]
      Interesting. However, according the DBD::mysql docs mysql_use_result "tends to block other processes." I'm not sure what that means exactly but it doesn't sound good! I think I'll stick with LIMIT and OFFSET...

      -sam

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Re: Re: Re: Re: It's bad manners to slurp
by mpeppler (Vicar) on Apr 29, 2004 at 16:03 UTC
    You're right - if you're stuck with a driver that behaves this way you need to be careful. IIRC it is configurable in DBD::mysql, don't know about DBD::Pg.

    Still - it's something that shows a fundamental lack of understanding of large-scale database management issues that this behavior is the default for these two drivers (and no, I don't know if it's the driver's fault or the underlying API)

    Michael

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