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Take into account the number of null values in any used column when

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calculating selectivity of conditions.
This commit is contained in:
Igor Babaev
2013-03-31 23:41:47 -07:00
parent cb47f0a79f
commit e370530493
4 changed files with 114 additions and 24 deletions
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44
sql/sql_statistics.cc
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@ -3342,25 +3342,41 @@ double get_column_range_cardinality(Field *field,
double res;
TABLE *table= field->table;
Column_statistics *col_stats= table->field[field->field_index]->read_stats;
double tab_records= table->stat_records();
if (!col_stats)
res= table->stat_records();
return tab_records;
double col_nulls= tab_records * col_stats->get_nulls_ratio();
double col_non_nulls= tab_records - col_nulls;
if (col_non_nulls < 1)
res= 0;
else if (min_endp && max_endp && min_endp->length == max_endp->length &&
!memcmp(min_endp->key, max_endp->key, min_endp->length))
{
double avg_frequency= col_stats->get_avg_frequency();
res= avg_frequency;
if (avg_frequency > 1.0 + 0.000001 &&
col_stats->min_value && col_stats->max_value)
if (field->null_ptr && min_endp->key[0])
{
Histogram *hist= &col_stats->histogram;
if (hist->get_size() > 0)
/* This is null single point range */
res= col_nulls;
}
else
{
double avg_frequency= col_stats->get_avg_frequency();
res= avg_frequency;
if (avg_frequency > 1.0 + 0.000001 &&
col_stats->min_value && col_stats->max_value)
{
double pos= field->middle_point_pos(col_stats->min_value,
col_stats->max_value);
res= table->stat_records() *
hist->point_selectivity(pos,
avg_frequency / table->stat_records());
Histogram *hist= &col_stats->histogram;
if (hist->get_size() > 0)
{
double pos= field->middle_point_pos(col_stats->min_value,
col_stats->max_value);
res= col_non_nulls *
hist->point_selectivity(pos,
avg_frequency / col_non_nulls);
}
}
}
}
@ -3394,10 +3410,10 @@ double get_column_range_cardinality(Field *field,
sel= (max_mp_pos - min_mp_pos);
else
sel= hist->range_selectivity(min_mp_pos, max_mp_pos);
res= table->stat_records() * sel;
res= col_non_nulls * sel;
}
else
res= table->stat_records();
res= col_non_nulls;
}
return res;
}