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Use better estimation methods for values that stats never saw #7127

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alivxxx opened this issue Jul 23, 2018 · 0 comments

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alivxxx commented Jul 23, 2018

When we query a value that the stats never saw, we will estimate as if they do not exist. However, we can use better estimation methods:

For equality queries, we can estimate them based on NDV.
For range queries, we can estimate them based on histograms and uniform spread assumptions.

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stats: refine the row count estimation for unknown values #7175

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coocood closed this as completed in #7175

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