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Fixed the bug that caused displaying incorrect values in

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the column cardinality of the table information_schema.statistics.
This commit is contained in:
Igor Babaev
2012-05-17 16:54:26 -07:00
parent 2a1afc29f2
commit 9b79feba56
5 changed files with 92 additions and 2 deletions
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37
mysql-test/r/stat_tables_innodb.result
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@@ -143,6 +143,43 @@ dbt3_s001 region PRIMARY 1 1
dbt3_s001 supplier PRIMARY 1 1
dbt3_s001 supplier i_s_nationkey 1 1.1111111111111112
dbt3_s001 supplier i_s_nationkey 2 1
select * from mysql.table_stat where table_name='orders';
db_name table_name cardinality
dbt3_s001 orders 1500
select * from mysql.index_stat where table_name='orders';
db_name table_name index_name prefix_arity avg_frequency
dbt3_s001 orders PRIMARY 1 1
dbt3_s001 orders i_o_orderdate 1 1.3321492007104796
dbt3_s001 orders i_o_orderdate 2 1
dbt3_s001 orders i_o_custkey 1 15
dbt3_s001 orders i_o_custkey 2 1
select (select cardinality from mysql.table_stat where table_name='orders') /
(select avg_frequency from mysql.index_stat
where index_name='i_o_orderdate' and prefix_arity=1) as n_distinct;
n_distinct
1126
select count(distinct o_orderdate) from orders;
count(distinct o_orderdate)
1126
select (select cardinality from mysql.table_stat where table_name='orders') /
(select avg_frequency from mysql.index_stat
where index_name='i_o_custkey' and prefix_arity=1) as n_distinct;
n_distinct
100
select count(distinct o_custkey) from orders;
count(distinct o_custkey)
100
show index from orders;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment
orders 0 PRIMARY 1 o_orderkey A 1500 NULL NULL BTREE
orders 1 i_o_orderdate 1 o_orderDATE A 1127 NULL NULL YES BTREE
orders 1 i_o_custkey 1 o_custkey A 100 NULL NULL YES BTREE
select index_name, column_name, cardinality from information_schema.statistics
where table_name='orders';
index_name column_name cardinality
PRIMARY o_orderkey 1500
i_o_orderdate o_orderDATE 1127
i_o_custkey o_custkey 100
set @save_optimizer_switch=@@optimizer_switch;
set optimizer_switch='index_condition_pushdown=off';
EXPLAIN select n_name, sum(l_extendedprice * (1 - l_discount)) as revenue