Fixed the bug that caused displaying incorrect values in

the column cardinality of the table information_schema.statistics.

mysql-test/r/stat_tables.result

@@ -118,6 +118,41 @@ dbt3_s001	partsupp	i_ps_suppkey	1	70
 dbt3_s001	region	PRIMARY	1	1
 dbt3_s001	supplier	PRIMARY	1	1
 dbt3_s001	supplier	i_s_nationkey	1	1.1111111111111112
+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_custkey	1	15
+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

mysql-test/r/stat_tables_innodb.result

@@ -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

mysql-test/t/stat_tables.test

@@ -69,6 +69,20 @@ FLUSH TABLE mysql.table_stat, mysql.index_stat;
 select * from mysql.table_stat;
 select * from mysql.index_stat;
 
+select * from mysql.table_stat where table_name='orders';
+select * from mysql.index_stat where table_name='orders';
+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; 
+select count(distinct o_orderdate) from orders;
+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;
+select count(distinct o_custkey) from orders; 
+show index from orders;
+select index_name, column_name, cardinality from information_schema.statistics
+  where table_name='orders';
+
 set @save_optimizer_switch=@@optimizer_switch;
 set optimizer_switch='index_condition_pushdown=off';
 

sql/sql_select.cc

@@ -14102,6 +14102,7 @@ create_tmp_table(THD *thd, TMP_TABLE_PARAM *param, List<Item> &fields,
   table->intersect_keys.init();
   table->keys_in_use_for_query.init();
   table->no_rows_with_nulls= param->force_not_null_cols;
+  table->read_stat.cardinality_is_null= TRUE;
 
   table->s= share;
   init_tmp_table_share(thd, share, "", 0, tmpname, tmpname);

sql/sql_show.cc

@@ -5441,9 +5441,12 @@ static int get_schema_stat_record(THD *thd, TABLE_LIST *tables,
     TABLE *show_table= tables->table;
     KEY *key_info=show_table->s->key_info;
     if (show_table->file)
+    {
       show_table->file->info(HA_STATUS_VARIABLE |
                              HA_STATUS_NO_LOCK |
                              HA_STATUS_TIME);
+      set_statistics_for_table(thd, show_table);
+    }
     for (uint i=0 ; i < show_table->s->keys ; i++,key_info++)
     {
       KEY_PART_INFO *key_part= key_info->key_part;
@@ -5474,8 +5477,8 @@ static int get_schema_stat_record(THD *thd, TABLE_LIST *tables,
           KEY *key=show_table->key_info+i;
           if (key->rec_per_key[j])
           {
-            ha_rows records=(show_table->file->stats.records /
+            ha_rows records=((double) show_table->stat_records() /
-                             key->rec_per_key[j]);
+                             key->real_rec_per_key(j));
             table->field[9]->store((longlong) records, TRUE);
             table->field[9]->set_notnull();
           }