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MDEV-27229: Estimation for filtered rows less precise ... #5

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Followup: remove this line from get_column_range_cardinality()

      set_if_bigger(res, col_stats->get_avg_frequency());

and make sure it is only used with the binary histograms.
For JSON histograms, it makes the estimates unnecessarily imprecise.
This commit is contained in:
Sergei Petrunia
2022-01-11 16:58:51 +03:00
parent d3e511d421
commit db8f15be93
7 changed files with 33 additions and 16 deletions
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13
sql/sql_statistics.cc
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@@ -3910,10 +3910,13 @@ double get_column_range_cardinality(Field *field,
if (col_stats->min_max_values_are_provided())
{
Histogram_base *hist= col_stats->histogram;
double avg_frequency= col_stats->get_avg_frequency();
double sel;
if (hist && hist->is_usable(thd))
{
sel= hist->range_selectivity(field, min_endp, max_endp);
sel= hist->range_selectivity(field, min_endp, max_endp,
avg_frequency / col_non_nulls);
res= col_non_nulls * sel;
}
else
{
@@ -3938,9 +3941,9 @@ double get_column_range_cardinality(Field *field,
max_mp_pos= 1.0;
sel = (max_mp_pos - min_mp_pos);
res= col_non_nulls * sel;
set_if_bigger(res, avg_frequency);
}
res= col_non_nulls * sel;
set_if_bigger(res, col_stats->get_avg_frequency());
}
else
res= col_non_nulls;
@@ -4076,7 +4079,8 @@ double Histogram_binary::point_selectivity(Field *field, key_range *endpoint,
double Histogram_binary::range_selectivity(Field *field,
key_range *min_endp,
key_range *max_endp)
key_range *max_endp,
double avg_sel)
{
double sel, min_mp_pos, max_mp_pos;
Column_statistics *col_stats= field->read_stats;
@@ -4105,6 +4109,7 @@ double Histogram_binary::range_selectivity(Field *field,
uint max= find_bucket(max_mp_pos, FALSE);
sel= bucket_sel * (max - min + 1);
set_if_bigger(sel, avg_sel);
return sel;
}