>I found a situation today where a query was slow. The execution plan was not using the index has it should. This is an index which is composed by several fields. The number of fields is two. So, this is a very simple index with two fields. A query to return five records took 31 seconds. So, I looked at the execution plan and saw that it was not using it. I generated the script to recreate that index. After that, the execution plan showed that it was using it and the query was immediate.
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>Is this some kind of index corruption?

Do you have a maintenance plan to re-build indexes (de-fragment)?