Re: PDO buffered query problem

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Stewart Duncan wrote:
Hi there,

I'm having some serious problems with the PHP Data Object functions. I'm trying to loop through a sizeable result set (~60k rows, ~1gig) using a buffered query to avoid fetching the whole set.

No matter what I do, the script just hangs on the PDO::query() - it seems the query is running unbuffered (why else would the change in result set size 'fix' the issue?). Here is my code to reproduce the problem:

<?php
$Database = new PDO(
    'mysql:host=localhost;port=3306;dbname=mydatabase',
    'root',
    '',
    array(
        PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION,
        PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true
    )
);

Don't you want it the other way around? You want it unbuffered so it doesn't get retrieved in mysql, send the whole result set to php then you can use it.

You want to start using it immediately - so make it unbuffered.


Either way if the result set is going to be large your MySQL's memory or PHP's memory may exceed. So if you use either you may need to fine-tune PHP by increasing the per process memory (memory_limit in php.ini) or MySQL.

In case you use unbuffered queries you cannot use transactions as far as I can recall.

--
Thodoris


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