Adding Index to Table may reduce performance of Some Select Statements ?

[srinik]

Guy’s,

Adding Index to Table may reduce performance of Some Select?

Thanks in advance,
Srini

[sybrandb@yahoo.com]

Re: Adding Index to Table may reduce performance of Some Select Statements ?

srinikande@yaho o.com (srinik) wrote in message news:<95100be7. 0401052035.6bcc ad52@posting.go ogle.com>...[color=blue]
> Guy’s,
>
> Adding Index to Table may reduce performance of Some Select?
>
> Thanks in advance,
> Srini[/color]

Vague response for a vague question without any sensible clue:
'it depends'

Sybrand Bakker
Senior Oracle DBA

[Daniel Roy]

Re: Adding Index to Table may reduce performance of Some Select Statements ?

To receive any useful information, you will certainly need to provide
additional details on your setup, or find someone more familiar with
your Oracle to do it for you. The cases where I saw that an additional
index slowed some select statements was generally when:
- rule-based optimizing is used and the new index has low cardinality
columns (few distinct values)
- cost-based optimizing is used, and the stats are not kept up-to-date
- cost-based optimizing is used, and the indexed columns suffer from
skewness, and no histograms are used.

Those are 3 examples, and is certainly not a complete list.

Daniel

srinikande@yaho o.com (srinik) wrote in message news:<95100be7. 0401052035.6bcc ad52@posting.go ogle.com>...[color=blue]
> Guy’s,
>
> Adding Index to Table may reduce performance of Some Select?
>
> Thanks in advance,
> Srini[/color]