Re: [HACKERS] Slow count(*) again...

On Thu, Feb 3, 2011 at 7:41 AM, Kenneth Marshall <ktm(at)rice(dot)edu> wrote:
> On Thu, Feb 03, 2011 at 02:11:58AM -0800, david(at)lang(dot)hm wrote:
>> On Thu, 3 Feb 2011, Vitalii Tymchyshyn wrote:
>>
>>> 02.02.11 20:32, Robert Haas ???????(??):
>>>> Yeah.  Any kind of bulk load into an empty table can be a problem,
>>>> even if it's not temporary.  When you load a bunch of data and then
>>>> immediately plan a query against it, autoanalyze hasn't had a chance
>>>> to do its thing yet, so sometimes you get a lousy plan.
>>>
>>> May be introducing something like 'AutoAnalyze' threshold will help? I
>>> mean that any insert/update/delete statement that changes more then x% of
>>> table (and no less then y records) must do analyze right after it was
>>> finished.
>>> Defaults like x=50 y=10000 should be quite good as for me.
>>
>> If I am understanding things correctly, a full Analyze is going over all
>> the data in the table to figure out patterns.
>>
>> If this is the case, wouldn't it make sense in the situation where you are
>> loading an entire table from scratch to run the Analyze as you are
>> processing the data? If you don't want to slow down the main thread that's
>> inserting the data, you could copy the data to a second thread and do the
>> analysis while it's still in RAM rather than having to read it off of disk
>> afterwords.
>>
>> this doesn't make sense for updates to existing databases, but the use case
>> of loading a bunch of data and then querying it right away isn't _that_
>> uncommon.
>>
>> David Lang
>>
>
> +1 for in-flight ANALYZE. This would be great for bulk loads of
> real tables as well as temp tables.

Yes, please, that would be really nice.

--
Jon