On Tue, Oct 14, 2014 at 11:20 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Sawada Masahiko <sawada.mshk@gmail.com> writes:
>> I found that the statistics are still remained after it's truncated.
>> In addition, the analyzing ignores table does not have any tuple.
>> After table truncated, the entry of statistics continues to remain
>> unless insertion and analyzing are executed.
>> There is reason why statistics are remained?
>
> Yes, actually, that's intentional. The idea is that once you start
> loading data into the table, it's most likely going to look something
> like the old data; therefore, the stale statistics are better than
> none at all. Eventually auto-ANALYZE will replace the stats,
> but until that happens, it seems best to keep using the old stats.
> (Of course there are counterexamples to this, but removing the stats
> is bad in more cases than not.)
>
>> Attached patch is one line patch adds RemoveStatistics() into
>> ExecuteTruncate(), to remove statistics entry of table.
>
> -1, for the reasons explained above.
>
I understood that reason.
Thank you for explaining!
--
Regards,
-------
Sawada Masahiko
