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Re: wrong output generate while using partitions
Posted by: Rick James
Date: December 17, 2014 11:27AM

> can you explain why index_merge is coming on partitioned table and not coming on non partitioned table?

No. Sounds like a bug in the code. A SELECT that touches multiple PARTITIONs has to gather results from the partitions and combine them. Perhaps in the case of index_merge, that "combining" occurs earlier -- during the index lookups.

> which require change in existing queries

5.7 will have a "Query Rewrite" feature that lets you do that without touching the code.

> create composite indexes

That is usually a better solution than depending on index_merge.

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Re: wrong output generate while using partitions
December 17, 2014 11:27AM

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