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| author | Sergei Petrunia <psergey@askmonty.org> | 2022-01-11 17:09:55 +0300 |
|---|---|---|
| committer | Sergei Petrunia <psergey@askmonty.org> | 2022-01-19 18:10:12 +0300 |
| commit | dae20dde4e7ae3ad6558eac9aa642fcccecaf13b (patch) | |
| tree | afe0ffcad411726940448cc2de3579f5f52a8a46 /sql/opt_histogram_json.cc | |
| parent | db8f15be93ff462b738101e7db89bd609455f0fa (diff) | |
| download | mariadb-git-dae20dde4e7ae3ad6558eac9aa642fcccecaf13b.tar.gz | |
MDEV-26901: Estimation for filtered rows less precise ... #4
In Histogram_json_hb::point_selectivity(), do return selectivity of 0.0
when the histogram says so.
The logic of "Do not return 0.0 estimate as it causes a multiply-by-zero
meltdown in cost and cardinality calculations" is moved into
records_in_column_ranges() where it is one *once* per column pair (as
opposed to doing once per range, which can cause the error to add-up
to large number when there are many ranges)
Diffstat (limited to 'sql/opt_histogram_json.cc')
| -rw-r--r-- | sql/opt_histogram_json.cc | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/sql/opt_histogram_json.cc b/sql/opt_histogram_json.cc index 4305737df1c..73284025511 100644 --- a/sql/opt_histogram_json.cc +++ b/sql/opt_histogram_json.cc @@ -921,7 +921,7 @@ double Histogram_json_hb::point_selectivity(Field *field, key_range *endpoint, The bucket has a single value and it doesn't match! Return a very small value. */ - sel= 1.0 / total_rows; + sel= 0.0; } else { |