Re: Performance Issue

Unique indexes ultimately take longer when massive updates are being done, because they need to check the entire index for a non-match before the record can be commited, else they error. On extremely large tables, that might make a difference.

Unique indexes, of course will speed up the performance of "access" or simply selecting data. That's what they're used for. Indexes are essentially a hash table that the db engine uses to directly address data (on disk or in memory). Another thing ... if the data fields you are selecting are all part of an index (in the same order, that's important), then the db engine doesn't even have to go to the table to get the data ... it's already in the index it just found.

• sooz

On Thu, 3 Sep 1998 22:42:08 -0400, "Roman Gelfand" <rgelfand_at_masmid.com> wrote:

>Could somebody tell me if unique as opposed to non-unique index will slow
>down updates and/or access and why?
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Received on Thu Sep 03 1998 - 22:03:33 CDT