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Cardinality estimates for out-of-range/non-existent value predicates

MarcusMonnigMar 30 2011 — edited Mar 30 2011
Hi!

Taken from a 10053 CBO trace file:
...
  Single Table Cardinality Estimation for MYTABLE[MYTABLE]
  Column (#30):
    NewDensity:0.000245, OldDensity:0.001190 BktCnt:254, PopBktCnt:8, PopValCnt:4, NDV:3962
  Using prorated density: 0.000245 of col #30 as selectvity of out-of-range/non-existent value pred
...
What is the rationale of the optimizer/optimizer developers using any denisty other than 0 for predicates that will return no rows? I don't seem to get it...

Thanks,
Marcus
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Locked on Apr 27 2011
Added on Mar 30 2011
#general-database-discussions
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