Re: Much slower DBI on RHEL6

Try running the query with the mysql commandline client to see whether you get a significant runtime difference. That way you could isolate the problem to mysql if possible.

In any case I don't see how the code could possibly work the way the comments indicate was intended. If 'id' is indeed a record ID as is customary in relational DBs, the DISTINCT does nothing. If not, it's indeed useful but then the results will be read one id at a time and nothing like "the hash will only keep one key but it will be the oldest one" happens. Then the same id is read again together with a single description. It looks like a

SELECT DISTINCT id,description from list_index
[download]

would do the same job. Or the whole script as

my $sql = 'SELECT DISTINCT id,description FROM list_index';
foreach(@{ $dbh->selectall_arrayref($sql, {Slice => {}}) }) {
    $labels{$_->{id}} =  "$_->{id} - $_->{description}";
}
[download]

If that doesn't help, try and check the DDL, i.e. the CREATE TABLE, especially the indices on both tables.

Comment on Re: Much slower DBI on RHEL6 Select or Download Code

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Re^2: Much slower DBI on RHEL6 by MPM (Novice) on Feb 05, 2014 at 23:04 UTC
perhaps some sample data would make things clearer `+---------+--------------------------------+--------------------+ \| id \| description \| rpt_key \| +---------+--------------------------------+--------------------+ \| ABC \| Organizational Detail Newer \| ABC.2013_10_18 \| \| ABC \| Organizational Detail Older \| ABC.2012_10_15 \| \| XYZ \| XYZ Status \| XYZ.2012_08_05 \| \| XYZ \| XYZ Status \| XYZ.2012_08_12 \| \| XYZ \| XYZ Status \| XYZ.2013_08_14 \| +---------+--------------------------------+--------------------+` [download] So the values I would want are: `ABC - Organizational Detail Newer XYZ - XYZ Status` [download]	[reply] [d/l] [select]
Re^2: Much slower DBI on RHEL6 by karlgoethebier (Abbot) on Feb 05, 2014 at 23:55 UTC
Mmh, may be. But how this cohere with the RHEL 5 vs RHEL 6 issue? Best regards, Karl ŤThe Crux of the Biscuit is the Apostropheť	[reply]
Re^3: Much slower DBI on RHEL6 by MPM (Novice) on Feb 06, 2014 at 02:38 UTC
sorry, not sure what you are asking here. I put sample db data and target result in response to show that the suggested query by mbethke wouldn't get the needed results... I think I was unclear on what the code should be doing	[reply]