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Bug#44059: Incorrect cardinality of indexes on a partitioned table

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backport for bug#44059 from mysql-pe to mysql-5.1-bugteam

Using the partition with most rows instead of first partition
to estimate the cardinality of indexes.
This commit is contained in:
Mattias Jonsson 2009-10-08 15:58:17 +02:00
parent d9ce9f215d
commit 27b80f9db8
3 changed files with 55 additions and 7 deletions
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15
mysql-test/r/partition.result
View file

@ -50,6 +50,21 @@ t1 CREATE TABLE `t1` (
PARTITION p3 VALUES LESS THAN (733969) ENGINE = MyISAM,
PARTITION pmax VALUES LESS THAN MAXVALUE ENGINE = MyISAM) */
DROP TABLE t1;
create table t1 (a int, b int, key(a))
partition by list (a)
( partition p0 values in (1),
partition p1 values in (2));
insert into t1 values (1,1),(2,1),(2,2),(2,3);
show indexes from t1;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment
t1 1 a 1 a A NULL NULL NULL YES BTREE
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status OK
show indexes from t1;
Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment
t1 1 a 1 a A 1 NULL NULL YES BTREE
drop table t1;
CREATE TABLE t1 (a INT, FOREIGN KEY (a) REFERENCES t0 (a))
ENGINE=MyISAM
PARTITION BY HASH (a);

13
mysql-test/t/partition.test
View file

@ -61,6 +61,19 @@ SELECT * FROM t1;
SHOW CREATE TABLE t1;
DROP TABLE t1;
#
# Bug#44059: rec_per_key on empty partition gives weird optimiser results
#
create table t1 (a int, b int, key(a))
partition by list (a)
( partition p0 values in (1),
partition p1 values in (2));
insert into t1 values (1,1),(2,1),(2,2),(2,3);
show indexes from t1;
analyze table t1;
show indexes from t1;
drop table t1;
#
# Bug#36001: Partitions: spelling and using some error messages
#

34
sql/ha_partition.cc
View file

@ -5011,8 +5011,9 @@ int ha_partition::info(uint flag)
If the handler doesn't support statistics, it should set all of the
above to 0.
We will allow the first handler to set the rec_per_key and use
this as an estimate on the total table.
We first scans through all partitions to get the one holding most rows.
We will then allow the handler with the most rows to set
the rec_per_key and use this as an estimate on the total table.
max_data_file_length: Maximum data file length
We ignore it, is only used in
@ -5024,14 +5025,33 @@ int ha_partition::info(uint flag)
ref_length: We set this to the value calculated
and stored in local object
create_time: Creation time of table
Set by first handler
So we calculate these constants by using the variables on the first
handler.
So we calculate these constants by using the variables from the
handler with most rows.
*/
handler *file;
handler *file, **file_array;
ulonglong max_records= 0;
uint32 i= 0;
uint32 handler_instance= 0;
file= m_file[0];
file_array= m_file;
do
{
file= *file_array;
/* Get variables if not already done */
if (!(flag & HA_STATUS_VARIABLE) ||
!bitmap_is_set(&(m_part_info->used_partitions),
(file_array - m_file)))
file->info(HA_STATUS_VARIABLE);
if (file->stats.records > max_records)
{
max_records= file->stats.records;
handler_instance= i;
}
i++;
} while (*(++file_array));
file= m_file[handler_instance];
file->info(HA_STATUS_CONST);
stats.create_time= file->stats.create_time;
ref_length= m_ref_length;