Populate a nulls fraction when NDV is known in TableScanStatsRule #15132
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If a connector provides NDV but is missing nulls fraction statistic for a column (e.g. Delta Lake after "delta.dataSkippingNumIndexedCols" columns and MySql), populate a 10% guess value so that the CBO can still produce some estimates rather than failing to make any estimates due to lack of nulls fraction.
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Minor comment. It would be better to use a full term instead of using an abbreviation(acronym) like NDV. |
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Description
If a connector provides NDV but is missing nulls fraction statistic for a column
(e.g. Delta Lake after "delta.dataSkippingNumIndexedCols" columns and MySql), populate a
10% guess value so that the CBO can still produce some estimates rather than
failing to make any estimates due to lack of nulls fraction.
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