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From:M5 Date:March 24 2007 9:26pm
Subject:Index not used sometimes -- why?
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Sometimes, when I run a query on a table, the index will be used. But  
if I run the SAME query, but on a larger set of rows (e.g., where id  
BETWEEN 1 AND 100000 vs WHERE id BETWEEN 1 AND 500), the index is not  
used. (EXPLAIN tells me this.) And as a result, the query runs slow.

The question I have is, why is the index not used on larger-range  
queries? Could it be because the key_buffer_size parameter is too  
small? Presently, it's set at the default value of 8M. Could  
increasing that value to, say, 128M, potentially solve this problem?  
Or is there some other factor involved?


Index not used sometimes -- why?M524 Mar
  • Re: Index not used sometimes -- why?Mathieu Bruneau25 Mar