Andreas Joseph Krogh < andreak@officenet.no> writes: > Will $SUBJECT make it possible for count(*) to use index? This is a much > wanted feature.
If you mean "count(*) will become instantaneous", no it won't. It would get faster, but probably not by more than a factor of 10 or so, corresponding to the size ratio between index and table. Remember that the proposal is going to bloat indexes pretty badly: a simple index on an int4 column will double in size, more or less. So that ratio will be much less favorable than it is today.
Personally I think the bloat problem will doom this entire approach. The distributed costs of that will outweigh the speedups that can be achieved for specific queries. The OP is free to try to prove this fear wrong, but no amount of discussion will constitute such a proof; only a testable implementation.
regards, tom lane
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