RE: Any quick way to remove histograms?

Nice.

FYI. An easy way to get the quotes right is instead of thinking about it, use ||''''|| every time you want one. (an escaped quote surrounded by quotes).
It's also easier to read and keep track of where you are.

select 'execute dbms_stats.set_column_stats('||''''||owner ||''''||','||''''||table_name||''''||','||''''||column_name||''''|| ',distcnt=>'||''''||num_distinct||''''||');' from all_tab_col_statistics where histogram <> 'NONE';

Joel Patterson
Database Administrator
joel.patterson_at_crowley.com
x72546
904 727-2546

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Allen, Brandon Sent: Monday, March 26, 2007 8:24 PM
To: Alberto Dell'Era; breitliw_at_centrexcc.com; oracle-l_at_freelists.org Subject: RE: Any quick way to remove histograms?

At first I was thinking that Alberto's procedure would still be required for retrieving the current stats and then resetting just the distcnt value. However, after thinking it through for a while, I realized what you were probably both thinking the whole time, which is that with this simplified method, you can just use a simple SELECT statement on all_tab_col_statistics to retrieve the current num_distinct value and plug it into the set_column_stats procedure for all columns that currently have histograms, thereby creating a script that can be used to very quickly remove all existing histograms. It took me a while to get all the single quotes just right, but here is the working version for anyone else that might find it helpful:

select 'execute dbms_stats.set_column_stats(''' || owner || ''',''' || table_name || ''',''' || column_name || ''', distcnt=>''' || num_distinct || ''');' from all_tab_col_statistics where histogram <> 'NONE'; Sample Output:

execute dbms_stats.set_column_stats('SCOTT','T','C1', distcnt=>'2421');
execute dbms_stats.set_column_stats('SCOTT','T','C2', distcnt=>'2425');
execute dbms_stats.set_column_stats('SCOTT','T','C3', distcnt=>'2421');

Thanks again to Wolfgang and Alberto!

Regards,
Brandon

-----Original Message-----
From: Alberto Dell'Era [mailto:alberto.dellera_at_gmail.com] Sent: Friday, March 16, 2007 4:43 PM
To: breitliw_at_centrexcc.com
Cc: Allen, Brandon; Oracle-L_at_freelists.org Subject: Re: Any quick way to remove histograms?

Much simpler :) - interesting.

On 3/16/07, Wolfgang Breitling <breitliw_at_centrexcc.com> wrote:
>
> I also did a quick check and just using
>
> exec
> dbms_stats.set_column_stats(user,'table_name',colname=>'column_name',d
> istcnt=>
> <num_distinct>);
>
> will remove the histogram without removing the low_value and
high_value.
>
>
>
> At 01:40 PM 3/16/2007, Alberto Dell'Era wrote:
> >On 3/16/07, Allen, Brandon <Brandon.Allen_at_oneneck.com> wrote:
> >>Is there any faster way to remove histograms other than re-analyzing

> >>the table? I want to keep the existing table, index & column stats,

> >>but with only 1 bucket (i.e. no histograms).
> >
> >You might try the attached script, that reads the stats using
> >dbms_stats.get_column_stats and re-sets them, minus the histogram,
> >using dbms_stats.set_column_stats.
> >
> >I haven't fully tested it - it's only 10 minutes old, even if I have
> >slightly modified for you another script I've used for quite some
> >time - and the spool on 10.2.0.3 seems to confirmthat the histogram
> >is, indeed, removed, while all the other statistics are preserved. I
> >have also reset density to 1/num_distinct, that is the value you get
> >if no histogram is collected.

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