Hi Tripp, all!
Tripp Bishop wrote:
[[...]]
Why would adding extra fields to the query slow the
query down so much? In either case it looks like it's
using the same index.
If a query is to return only fields contained in the index, it can be
executed as an "index-only" query, and the "true" data need not be accessed.
The moment you ask for a field not contained in the index, for each
index entry matching the search condition, the base data need to be
accessed to get that field.
This may be very significant additional costs.
HTH,
Joerg
PS:
In my reader, it looked like your original question hijacked another
thread: "Question regarding running 'mysql' from a bash script".
:-(
--
Joerg Bruehe, Senior Production Engineer
MySQL AB, www.mysql.com
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