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Re: I searched table on one partiton, but MySQL scanning two partitons
Posted by: Rick James ()
Date: March 04, 2012 02:28PM

Yes. Note that the extra one is always the first partition. Note what happens with invalid DATETIME strings:
mysql> SELECT TO_DAYS('2011-02-29'), TO_DAYS('2012-02-29');
+-----------------------+-----------------------+
| TO_DAYS('2011-02-29') | TO_DAYS('2012-02-29') |
+-----------------------+-----------------------+
|                  NULL |                734927 |
+-----------------------+-----------------------+
1 row in set, 1 warning (0.00 sec)
NULLs (and zeros) go into the first parition (because of the LESS THAN clause).

The standard recommendation is to have nothing deliberately in the first partition. That is, start the partitions you really want with the second partition. That way, the cost of the seemingly spurious reach into the empty pmin will be minimal.

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Subject Views Written By Posted
I searched table on one partiton, but MySQL scanning two partitons 1559 Yang Bingle 03/03/2012 04:01AM
Re: I searched table on one partiton, but MySQL scanning two partitons 889 Rick James 03/04/2012 02:28PM


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