On 2015-07-20 12:18, Petr Jelinek wrote:
> On 2015-07-19 22:56, Tom Lane wrote:
>>
>> * You might have expected me to move the tsmseqscan and tsmpagemode flags
>> into the TsmRoutine struct, but instead this API puts equivalent flags
>> into the SampleScanState struct. The reason for that is that it lets
>> the settings be determined at runtime after inspecting the TABLESAMPLE
>> parameters, which I think would be useful. For example, whether to use
>> the bulkread strategy should probably depend on what the sampling
>> percentage is.
>>
>
> I think this ignores one aspect of the old API. That is, we allowed the
> sampling method to specify which kind of input parameters it accepts.
> This is why for example the tsm_system_rows accepts integer while system
> and bernoulli both accept float8. This part of the API is certainly not
> needed for bernoulli and system sampling but if we ever want to do
> something more sophisticated like stratified sampling which Simon
> mentioned several times, specifying just percentages is not going to be
> enough.
>
Actually I see the tsmapi has support for this, so please ignore the noise.
-- Petr Jelinek http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training &
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