Re: Oracle recent version improves bind variable performance?

On Sep 18, 12:13 pm, Luch <DarthL..._at_gmail.com> wrote:
> In another thread I was reporting how a query I do with bind variables
> performs worse than an equivalent query done via strings.. One person
> responded that a more recent version of Oracle improves upon this. I
> started a new post because I wanted to ask about that... I definitely
> want to know about this if it is true so I can try the new version.
>
> I'm running Oracle 10.2.0.1.0 on Windows platform.
>
> Is there a newer version or patch that makes Oracle perform queries
> better, that use bind variables?
>
> This was the previous post:
>
> : We have a PowerBuilder application where we started noticing the
> : performance of a query is worse if you do it with bind variables
> then
> : if you do the same query as a string.
>
> Bind variables minimize the number of times a query must be parsed.
> That
> is likely to speed up your application if the same queries are used
> multiple times.
>
> Hard coded values allow the optimizer to select the best possible path
> to
> select the data. That is likely to speed up your application if a
> query
> is only run once, or if the time to parse the query is small compared
> to
> the time it takes to run the query, especially if the values are
> unusual
> compared to most of the data.
>
> Apparently more recent versions of Oracle (version?) will examine the
> values of bind variables before running a query as a sanity check that
> the
> existing parsed query will still be sensible for those values. I know
> not
> the exact details.

Oracle 10g (which includes 10.2.0.1) performs bind variable peeking on the initial hard parse (checking the value of a bind variable, just as if a constant were passed), and potentally on future parse calls from the client. Oracle 10g also automatically creates histograms, which help determine how frequently particular values occur in columns - this can also influence the execution plan. If the first parse call included bind variable values with uncommon values, a poor execution plan may be used for future execution calls with different bind variable values. If that frequently happens, it may be necessary to disable bind variable peeking to regain performance.

Charles Hooper
IT Manager/Oracle DBA
K&M Machine-Fabricating, Inc. Received on Tue Sep 18 2007 - 12:20:16 CDT