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Message Posted: Wed, 18 Dec 2003 @ 01:23:36 GMT

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Subj:   Re: Collect Stats on Single Column SI
From:   Christie, Jon

No, exactly the same thing. Well... Almost.

You pose an interesting question. When you drop a secondary index, the rows in DBC.Indexes defining that index will be deleted from the table. The statistics are stored in those rows, so they'll go too. If it was a single-column index, the stats would be stored in DBC.TVFields. I've never checked to see if they're removed or not. I'd assume that they are. Guess I'd have to take a look at an explain.

If you collect stats on multiple columns using the columns syntax, we put dummy rows in DBC.Indexes as though there were a secondary index, but we never build a secondary index subtable. Now if you happen to have a secondary index on the same columns, the stats should not go away if you drop the index. That's why I said almost.

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