[EMAIL PROTECTED] wrote:
Jigal van Hemert <[EMAIL PROTECTED]> wrote on 11/02/2005 03:29:14 AM:
> If I understand
> http://dev.mysql.com/doc/refman/5.0/en/table-and-index.html
> correctly, the index of the primary key is stored as the clustered index
> together with the data. To me this means that there is no difference
> between counting the primary key entries and counting the data entries.
>
That would be true if everyone could always see every record. However
there could be several active copies (versions) of any record. Each copy
would be part of a different transaction. How many records YOU can see
can be very different than how many records I can see depending on
what's going on in our respective transactions.
Sorry for the late reply, I had a day off.
I was talking about the difference between COUNT(*) and COUNT(<primary
key field>); I don't think that there is a difference in speed if you
take "snapshots" -- as InnoDB calls them -- into account. If the primary
key and the record data are stored together both counts should be
equally fast, no matter how many versions of a record exist.
Regards, Jigal.
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