The SELECT would examine more than MAX_JOIN_SIZE rows

[Debianer]

Hey everybody,
I get every hour this error mail:

Invalid SQL:

SELECT pmtext.pmtextid
FROM pmtext AS pmtext
LEFT JOIN pm AS pm USING(pmtextid)
WHERE pm.pmid IS NULL;

MySQL-Fehler : The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is okay
Fehler-Nr. : 1104
Fehler-Zeit : Monday, 21.07.2009 @ 12:21:32

The size of max_join_size on the server:

max_join_size 201326592

It is a hosted package and I cannot increase the size.

Are there any alternatives? What can I do?

Thanks for your help.

[Jake Bunce]

If your host won't change those settings then there isn't anything else you can do. You would have to change hosts.

[Debianer]

Thank you for your answer.
I have found out that SQL_BIG_SELECTS is OFF.

Where I can add SQL_BIG_SELECTS=1?
Would that help?

[Jake Bunce]

I don't know of any way to set that in vBulletin. AFAIK it needs to be set on the server.

[Debianer]

If I try this in in phpMyAdmin it seems to work:

SET SQL_BIG_SELECTS=1

SELECT pmtext.pmtextid
FROM pmtext AS pmtext
LEFT JOIN pm AS pm USING(pmtextid)
WHERE pm.pmid IS NULL;

Maybe I can set it at the DB connection part in vB?

[Debianer]

My solution at the moment:
I have added this in cleanup2.php:

$vbulletin->db->query_write("
    SET SQL_BIG_SELECTS=1"
);

Before:

$pmtexts = $vbulletin->db->query_read("
    SELECT pmtext.pmtextid
    FROM " . TABLE_PREFIX . "pmtext AS pmtext
    LEFT JOIN " . TABLE_PREFIX . "pm AS pm USING(pmtextid)
    WHERE pm.pmid IS NULL
");

It works but is that okay or could it be a problem?
Would it be better to add it generally e.g. in class_core.php at the connection part?

Thank you.

Edit:
The Query runs for 50 minutes and I think it would be better to run the Query not every hour but once every night.
Does this work without problems? Every hour is too often I think.