Hi!
>>>>> "Rick" == Rick James <rjames@stripped> writes:
Rick> (below)
Rick> Rick James
Rick> MySQL Geeks - Consulting & Review
>> From: Michael Widenius [mailto:monty@stripped]
Rick> ...
>> Assume you have in an InnoDB table and an index on (b,c) and 'a' is
>> the primary key. In this case:
>>
>> select c from foo where a=1 and b = 1
>>
>> I't better to scan the index (b,c) than scan the primary key as you
>> get all key parts from this index, but it's much less to scan as you
>> don't have to access all the other columns from the table.
Rick> True. I was assuming the indexes were limited to clustered indexes on
Rick> just one key each.
Rick> * Both a and b are clustered: Again, the other key is
>> useless; simply use the clustered key.
>>
>> How can you have something clustered on to different key?
>> (Normally you can only cluster on one key at a time)
Rick> The thread started by proposing the radical approach of having multiple
Rick> clustered indexes. This is a departure from all(?) existing engines.
Rick> The implementation is effectively multiple copies of the entire dataset,
Rick> just sorted in different ways.
<cut>
I must have missed the start of the thread; Thanks a lot for the
explanation and the example!
Regards,
Monty
