Take into account the number of null values in any used column when
calculating selectivity of conditions.
This commit is contained in:
Igor Babaev
parent
cb47f0a79f
commit
e370530493
@ -6,12 +6,37 @@ select @@session.use_stat_tables;
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COMPLEMENTARY
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set @save_use_stat_tables=@@use_stat_tables;
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set use_stat_tables='preferably';
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DROP DATABASE IF EXISTS dbt3_s001;
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CREATE DATABASE dbt3_s001;
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use dbt3_s001;
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set @save_optimizer_use_condition_selectivity=@@optimizer_use_condition_selectivity;
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set @save_histogram_size=@@histogram_size;
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set @save_histogram_type=@@histogram_type;
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set optimizer_use_condition_selectivity=3;
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create table t1 (a int);
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insert into t1 values
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(9), (3), (2), (NULL), (NULL), (2), (NULL), (1), (5), (NULL);
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analyze table t1;
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Table Op Msg_type Msg_text
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test.t1 analyze status OK
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select * from mysql.column_stats;
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db_name table_name column_name min_value max_value nulls_ratio avg_length avg_frequency hist_size hist_type histogram
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test t1 a 1 9 0.4000 4.0000 1.2000 0 NULL NULL
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flush table t1;
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explain extended
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select * from t1 where a is null;
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id select_type table type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 10 40.00 Using where
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Warnings:
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Note 1003 select `test`.`t1`.`a` AS `a` from `test`.`t1` where isnull(`test`.`t1`.`a`)
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explain extended
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select * from t1 where a is not null;
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id select_type table type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 10 60.00 Using where
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Warnings:
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Note 1003 select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` is not null)
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drop table t1;
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set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
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DROP DATABASE IF EXISTS dbt3_s001;
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CREATE DATABASE dbt3_s001;
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use dbt3_s001;
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=== Q15 ===
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create view revenue0 (supplier_no, total_revenue) as
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select l_suppkey, sum(l_extendedprice * (1 - l_discount))
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@ -9,12 +9,37 @@ select @@session.use_stat_tables;
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COMPLEMENTARY
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set @save_use_stat_tables=@@use_stat_tables;
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set use_stat_tables='preferably';
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DROP DATABASE IF EXISTS dbt3_s001;
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CREATE DATABASE dbt3_s001;
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use dbt3_s001;
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set @save_optimizer_use_condition_selectivity=@@optimizer_use_condition_selectivity;
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set @save_histogram_size=@@histogram_size;
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set @save_histogram_type=@@histogram_type;
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set optimizer_use_condition_selectivity=3;
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create table t1 (a int);
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insert into t1 values
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(9), (3), (2), (NULL), (NULL), (2), (NULL), (1), (5), (NULL);
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analyze table t1;
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Table Op Msg_type Msg_text
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test.t1 analyze status OK
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select * from mysql.column_stats;
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db_name table_name column_name min_value max_value nulls_ratio avg_length avg_frequency hist_size hist_type histogram
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test t1 a 1 9 0.4000 4.0000 1.2000 0 NULL NULL
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flush table t1;
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explain extended
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select * from t1 where a is null;
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id select_type table type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 10 40.00 Using where
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Warnings:
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Note 1003 select `test`.`t1`.`a` AS `a` from `test`.`t1` where isnull(`test`.`t1`.`a`)
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explain extended
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select * from t1 where a is not null;
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id select_type table type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE t1 ALL NULL NULL NULL NULL 10 60.00 Using where
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Warnings:
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Note 1003 select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` is not null)
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drop table t1;
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set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
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DROP DATABASE IF EXISTS dbt3_s001;
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CREATE DATABASE dbt3_s001;
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use dbt3_s001;
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=== Q15 ===
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create view revenue0 (supplier_no, total_revenue) as
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select l_suppkey, sum(l_extendedprice * (1 - l_discount))
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@ -7,6 +7,34 @@ set @save_use_stat_tables=@@use_stat_tables;
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set use_stat_tables='preferably';
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set @save_optimizer_use_condition_selectivity=@@optimizer_use_condition_selectivity;
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set @save_histogram_size=@@histogram_size;
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set @save_histogram_type=@@histogram_type;
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# check that statistics on nulls is used
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set optimizer_use_condition_selectivity=3;
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create table t1 (a int);
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insert into t1 values
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(9), (3), (2), (NULL), (NULL), (2), (NULL), (1), (5), (NULL);
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analyze table t1;
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select * from mysql.column_stats;
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flush table t1;
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explain extended
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select * from t1 where a is null;
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explain extended
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select * from t1 where a is not null;
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drop table t1;
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set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
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--disable_warnings
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DROP DATABASE IF EXISTS dbt3_s001;
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--enable_warnings
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@ -15,10 +43,6 @@ CREATE DATABASE dbt3_s001;
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use dbt3_s001;
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set @save_optimizer_use_condition_selectivity=@@optimizer_use_condition_selectivity;
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set @save_histogram_size=@@histogram_size;
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set @save_histogram_type=@@histogram_type;
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--disable_query_log
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--disable_result_log
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--disable_warnings
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@ -3342,25 +3342,41 @@ double get_column_range_cardinality(Field *field,
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double res;
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TABLE *table= field->table;
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Column_statistics *col_stats= table->field[field->field_index]->read_stats;
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double tab_records= table->stat_records();
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if (!col_stats)
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res= table->stat_records();
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return tab_records;
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double col_nulls= tab_records * col_stats->get_nulls_ratio();
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double col_non_nulls= tab_records - col_nulls;
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if (col_non_nulls < 1)
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res= 0;
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else if (min_endp && max_endp && min_endp->length == max_endp->length &&
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!memcmp(min_endp->key, max_endp->key, min_endp->length))
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{
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double avg_frequency= col_stats->get_avg_frequency();
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res= avg_frequency;
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if (avg_frequency > 1.0 + 0.000001 &&
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col_stats->min_value && col_stats->max_value)
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if (field->null_ptr && min_endp->key[0])
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{
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Histogram *hist= &col_stats->histogram;
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if (hist->get_size() > 0)
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/* This is null single point range */
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res= col_nulls;
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}
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else
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{
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double avg_frequency= col_stats->get_avg_frequency();
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res= avg_frequency;
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if (avg_frequency > 1.0 + 0.000001 &&
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col_stats->min_value && col_stats->max_value)
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{
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double pos= field->middle_point_pos(col_stats->min_value,
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col_stats->max_value);
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res= table->stat_records() *
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hist->point_selectivity(pos,
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avg_frequency / table->stat_records());
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Histogram *hist= &col_stats->histogram;
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if (hist->get_size() > 0)
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{
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double pos= field->middle_point_pos(col_stats->min_value,
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col_stats->max_value);
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res= col_non_nulls *
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hist->point_selectivity(pos,
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avg_frequency / col_non_nulls);
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}
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}
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}
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}
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@ -3394,10 +3410,10 @@ double get_column_range_cardinality(Field *field,
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sel= (max_mp_pos - min_mp_pos);
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else
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sel= hist->range_selectivity(min_mp_pos, max_mp_pos);
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res= table->stat_records() * sel;
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res= col_non_nulls * sel;
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}
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else
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res= table->stat_records();
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res= col_non_nulls;
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}
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return res;
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}
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