ID: 40261
User updated by: thuejk at gmail dot com
Reported By: thuejk at gmail dot com
Status: Open
Bug Type: Performance problem
Operating System: Linux
PHP Version: 5.2.0
New Comment:
On second though, black boxes are not good for testing. A simpler timer
added...
Previous Comments:
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[2007-01-28 01:47:01] thuejk at gmail dot com
I have made it a bit shorter.
I left the DebugStats class in, it is useful. Just treat it as a black
box. I can garantie that the two calls into it does not account for the
8 seconds performance problem...
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[2007-01-28 01:30:33] tony2001@php.net
Could please modify the script, so that it would be _short_ but
complete?
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[2007-01-28 01:25:13] thuejk at gmail dot com
I added the requested changes to the linked file
http://thuejk.dk/test.php.txt
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[2007-01-28 01:15:25] tony2001@php.net
Thank you for this bug report. To properly diagnose the problem, we
need a short but complete example script to be able to reproduce
this bug ourselves.
A proper reproducing script starts with <?php and ends with ?>,
is max. 10-20 lines long and does not require any external
resources such as databases, etc. If the script requires a
database to demonstrate the issue, please make sure it creates
all necessary tables, stored procedures etc.
Please avoid embedding huge scripts into the report.
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[2007-01-28 00:30:02] thuejk at gmail dot com
Description:
------------
I have some code which produces unacceptible performance in a specific
situation. Making a completely trivial change improves performance a
hundred-fold or more.
The problem is 100% reproducible.
The code looks something like:
/* pseudocode*/
function get_data_from_pgsql(){
...
$map = Array();
foreach ($rows as $row) {
$map = row[index];
}
return $map;
}
$data1 = get_data_from_pgsql
$data2 = get_data_from_pgsql
One run with 10000 rows of result took 8.77 seconds, which is clearly
silly. Making the extremely trivial change of moving the code block
foreach ($rows as $row) {
$map = row[index];
}
out of the function get_data_from_pgsql(), the code suddently only
takes 0.1 seconds to run (factor 90)! Having more rows in the result
makes the factor difference larger; it seems to increase
quadratically.
Not saving the return values in $data1 and $data2 also improves
performance immensely.
PHP 5.1.5 did not have this problem (or at least it was much smaller).
Reproduce code:
---------------
http://thuejk.dk/test.php.txt
You need a running postgresql database with one table, which has at
least 10000 entries.
change the line
$translate_outside_function = false;
at the top of the file to see the difference mentioned above.
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Edit this bug report at http://bugs.php.net/?id=40261&edit=1