Обсуждение: Massive delete of rows, how to proceed?

Hi all,

   I have a table with statistics with more than 15 million rows. I'd
like to delete the oldest statistics and this can be about 7 million
rows. Which method would you recommend me to do this? I'd be also
interested in calculate some kind of statistics about these deleted
rows, like how many rows have been deleted for date. I was thinking in
creating a function, any recommendations?

Thank you very much
--
Arnau

On 24/11/06, Arnau <arnaulist@andromeiberica.com> wrote:
> Hi all,
>
>    I have a table with statistics with more than 15 million rows. I'd
> like to delete the oldest statistics and this can be about 7 million
> rows. Which method would you recommend me to do this? I'd be also
> interested in calculate some kind of statistics about these deleted
> rows, like how many rows have been deleted for date. I was thinking in
> creating a function, any recommendations?


Copy and drop old table. If you delete you will have a massive problem
with a bloated table and  vacuum will not help unless you expect the
table to grow to this size regulally otherwise vacuum full will take
ages.

Peter.

On 11/25/06, Arnau <arnaulist@andromeiberica.com> wrote:
> Hi all,
>
>    I have a table with statistics with more than 15 million rows. I'd
> like to delete the oldest statistics and this can be about 7 million
> rows. Which method would you recommend me to do this? I'd be also
> interested in calculate some kind of statistics about these deleted
> rows, like how many rows have been deleted for date. I was thinking in
> creating a function, any recommendations?

a function, like an sql statement, operates in a single transaction
and you are locking quite a few records in this operation.  merlin's
3rd rule: long running transactions are (usually) evil.

my gut says moving the keeper records to a swap table, dropping the
main table, and swapping the tables back might be better.  However,
this kind of stuff can cause problems with logged in sessions because
of plan issues, beware.

do not write a function to delete records row by row unless you have
exhausted all other courses of action.

merlin