Re: Re: Re: Re: It's bad manners to slurp

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}.

Comment on Re: Re: Re: Re: It's bad manners to slurp Download Code

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Re: Re: Re: Re: Re: It's bad manners to slurp by eserte (Deacon) on Apr 29, 2004 at 17:12 UTC
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]
Re: Re: Re: Re: Re: Re: It's bad manners to slurp by samtregar (Abbot) on Apr 29, 2004 at 20:03 UTC
Care to elaborate? I'm unfamiliar with HANDLER. -sam	[reply]
Re: Re: Re: Re: Re: Re: Re: It's bad manners to slurp by eserte (Deacon) on Apr 30, 2004 at 12:24 UTC
It's some kind of low-level SELECT. You can't do complex queries or joins with HANDLER. You can just walk the table from the beginning to the end, optionally by using simple restrictions like > or =. The result of a "HANDLER READ" statement is a complete row, there's no way to select single rows. The advantage is speed and less memory consumption.	[reply]
Re: Re: Re: Re: Re: It's bad manners to slurp by samtregar (Abbot) on Apr 29, 2004 at 17:06 UTC
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	[reply]


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