As I said, if the columns did not have histograms in 8i I would not create
histograms in 9i.
I do no a-priori create a histogram on a column. ONLY if the analysis of a
sql performance problem indicates that a histogram is indicated.
In 9i you also can query sys.col_usage$ to find candidates for histograms.
That is what Oracle does when you request "method_opt => 'for ... columns
size auto' ".
At 02:51 PM 3/1/2004, you wrote:
yeah good idea. how do you determine which columns need histograms? I have 100s of tables in my applications and I do not have time to determine it. I typically have them run over night. ----- Original Message ----- From: "Wolfgang Breitling" <breitliw@xxxxxxxxxxxxx> To: <oracle-l@xxxxxxxxxxxxx> Sent: Monday, March 01, 2004 2:17 PM Subject: Re: RE: query slow in 9i, but not slow in 8i
> I would NOT do that. "method_opt='FOR ALL COLUMNS'" will collect histograms > of (default) size 75 for ALL columns of the table. At best that would be a > waste of time and resources, but it could easily be rather detrimental to > access paths. You do NOT want to collect histograms unless it is warranted. > > If the columns did not have histograms in 8i, I would not suddenly create > any in 9i. >
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