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Message Posted: Fri, 25 Nov 2011 @ 18:52:29 GMT

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Subj:   Re: Performance issue after splitting the big table
From:   Walter, Todd

PPI would not help select rows from the table but it would avoid the need to materialize the table via the UNION prior to executing the rest of the query.

In the case of your queries by region, this is where you should make sure that the CHECK constraints are in place on the region column. This will allow the optimizer to recognize that the other tables do not have to be accessed.

If your query is materializing the UNION before doing the rest of the query, then the only solution is to rewrite the query to execute the query against each of the tables and union the results rather than just executing against the UNION view. Much more complex for the query writer but more performant.

The optimizer keeps getting more smarts in this area in the most recent releases but there are still cases where we will materialize the UNION.

Also consider if you are collecting stats too often, on too many columns of multi-column sets, not using SAMPLE when appropriate,...

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