There surely is some "cost" involved in evaluating a histogram during the
parse phase, but I doubt that it will be significant enough to be
measurable. But histograms change the estimates of the CBO and it is quite
possible that the presence of a histogram on a column where the content is
not skewed enough to really warrant a histogram can change the estimates
enough to cause the optimizer to use a different, slower access path than
without the histogram.
At 09:14 PM 3/1/2004, you wrote:
I am unfortunately speaking from heresay, however I heard once that having histograms all over the place can slow down parsing as they have to be inspected. I was left with the impression that unless the data is skewed enough to warrant a histogram then there actually is a negative cost associated with having too many histograms.
Surely someone on this list can either support me or shoot me down on this one?
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