Re: ANALYZE sampling is too good

On 11/12/13 09:19, Heikki Linnakangas wrote:
> On 12/10/2013 10:00 PM, Simon Riggs wrote:
>> On 10 December 2013 19:54, Josh Berkus <josh@agliodbs.com> wrote:
>>> On 12/10/2013 11:49 AM, Peter Geoghegan wrote:
>>>> On Tue, Dec 10, 2013 at 11:23 AM, Simon Riggs 
>>>> <simon@2ndquadrant.com> wrote:
>>>> I don't think that anyone believes that not doing block sampling is
>>>> tenable, fwiw. Clearly some type of block sampling would be preferable
>>>> for most or all purposes.
>>>
>>> As discussed, we need math though.  Does anyone have an ACM 
>>> subscription
>>> and time to do a search?  Someone must.  We can buy one with community
>>> funds, but no reason to do so if we don't have to.
>>
>> We already have that, just use Vitter's algorithm at the block level
>> rather than the row level.
>
> And what do you do with the blocks? How many blocks do you choose? 
> Details, please.
>
>

Yeah - and we seem to be back to Josh's point about needing 'some math' 
to cope with the rows within a block not being a purely random selection.

Regards

Mark