On 2015-07-12 18:02, Tom Lane wrote:
A possible way around this problem is to redefine the sampling rule so that it is not history-dependent but depends only on the tuple TIDs. For instance, one could hash the TID of a candidate tuple, xor that with a hash of the seed being used for the current query, and then select the tuple if (hash/MAXINT) < P.
That would work for bernoulli for physical tuples, yes. Only thing that worries me is future extensibility for data sources that only provide virtual tuples.
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