On Tue, 13 May 2008, Michael Mayer wrote:
[EMAIL PROTECTED] wrote:
Unlikely, unless you have more writes than reads, which would be rather
unusual for most applications. :)
An index on a field with a selectivity of more than 15% can perform worse
than a full table scan in most cases. That affects read performance as well
as disk I/O and locks the table/rows for write access. Also, there is an
index on mailbox_idnr plus one on mailbox_idnr AND status (in that order),
which doesn't make sense, if the index is not a hash but a btree. That is btw
the only index type for InnoDB. So the case is clear.
The case isn't clear until you can post a direct comparison where a particular
query frequently used by the system runs faster without some of the said
indices than it does with them. Remember that the DB engine is free to decide
what indices to use and which to ignore. An unused index wastes little other
than additional space on disk.
Anyway, the original poster said there is only one server being used, so all
this replication/clustering is irrelevant in this particular case.
A cluster always is the last thing that helps. I did not recommend that. But
a cache is for sure not the worst idea one could come up with ;)
Absolutely agreed. And for the sake of enabling a switch in my.cnf it's worth
trying, if it's not enabled already.
Gordan
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