Re: Thinking About Correlated Columns (again)

On 05/15/2013 03:31 PM, Thomas Kellerer wrote:

> What happens if you create one index for each column? (instead of one
>  combined index)

I just created the combined index to simplify the output. With two
indexes, it does the usual bitmap index scan. Even then the row estimate
is off by a factor of 1000, which is the actual problem.

The other reason I tried the combined index was that there was some
noise a while back about having the planner check for possible column
correlations on composite indexes. Clearly that ended up not being the
case, but it was worth examination.

--
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-676-8870
sthomas@optionshouse.com

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