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From:Michael Widenius Date:July 19 2009 5:41pm
Subject:RE: help with index_merge and clustering keys
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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

Thread
help with index_merge and clustering keysZardosht Kasheff23 Jun
  • Re: help with index_merge and clustering keysZardosht Kasheff9 Jul
    • Re: help with index_merge and clustering keysSergey Petrunya10 Jul
      • Re: help with index_merge and clustering keysZardosht Kasheff10 Jul
        • RE: help with index_merge and clustering keysRick James10 Jul
          • RE: help with index_merge and clustering keysMichael Widenius16 Jul
            • Re: help with index_merge and clustering keysZardosht Kasheff16 Jul
            • RE: help with index_merge and clustering keysRick James16 Jul
              • RE: help with index_merge and clustering keysMichael Widenius19 Jul
        • Re: help with index_merge and clustering keysSergey Petrunya12 Jul
          • Re: help with index_merge and clustering keysZardosht Kasheff12 Jul
            • Re: help with index_merge and clustering keysSergey Petrunya15 Jul
              • RE: help with index_merge and clustering keysRick James15 Jul
              • Re: help with index_merge and clustering keysZardosht Kasheff24 Jul
      • Re: help with index_merge and clustering keysMichael Widenius16 Jul
Re: help with index_merge and clustering keysZardosht Kasheff10 Jul
Re: help with index_merge and clustering keysZardosht Kasheff16 Jul
  • RE: help with index_merge and clustering keysRick James16 Jul
    • Re: help with index_merge and clustering keysZardosht Kasheff16 Jul