Ignoring where clause

Anon

Odd thing happened today.

I have a script that runs in cron. It queries the database (MySQL) and then acts on the information retrieved.

This script hasn't changed in months.

Today for some reason, the database appeared to ignore the where clause and returned all the records when the script ran.

Any ideas? Is this a known problem?

[deleted]

Most likely the data change so that the where clause nolonger does what you want.

Run the query manually and see what happens.
What kind of where clause did you put in?

Anon

The data hasn't changed (that was the first thing I checked).

The Where clause is "WHERE Sent = 0"

This script has been running for 10 months without problems. Suddenly today, it did this. It's odd...

Running the query manually returns the expected results.

[deleted]

So if you run that query manually you get the correct data, and when you run it from the cron it ignores the where clause.

Can you verify that it is in fact running that query, and it's not chopping the where clause of through some freak syntax error?

And that the crontab script is still using the right database?

Anon

Running it from cron now, it gets the right data. It was just that one time this morning where it appeared to lose its WHERE clause.

Anon

Is this a single static query like:

$query = "select * from table where field=0

Or do you build it like:

$query = "select * from table ";
if (somecondition){
$query .= "where field=0";
} else {

}

???

I.e. if you're absolutly sure that the query you think ran and it did get the wrong result, then I have to say that's quite scary, like that horrible MSSQL bug where sometimes it returned only part of a select set if the set was large and you had a complex where clause, and it threw no errors.

databases giving wrong answers while throwing answers is acceptable, at least then you can abort the transaction or whatever, but throwing the wrong answers, unpredictable to boot, is just unforgiveable.

Do your logs say anything?

Anon

The query is static.

I've trawled through the MySQL error log, the logs generated by my script, the messages log, etc. Nothing untoward in any of them.

And as I say - nothing has been changed since it happened and now it is running fine.

Anon

Do your logs show some sort of heavy use at that moment? Perhaps your machine was under heavy strain when it tried to run the cronjob, resulting in unpredictable results?

Anon

The box wasn't under any particularly unusual load... it is a dedicated box, all it does is run MySQL and a few PHP scripts in cron. No webserver or anything on it. 1 GHz, 1Gig of RAM.