SHOW STATS_HISTOGRAMS

July 19, 2024 ยท View on GitHub

This statement shows the histogram information collected by the ANALYZE statement as part of database statistics.

Currently, the SHOW STATS_HISTOGRAMS statement returns the following columns:

Column nameDescription
Db_nameDatabase name
Table_nameThe table name
Partition_nameThe partition name
Column_nameThe column name (when is_index is 0) or the index name (when is_index is 1)
Is_indexWhether it is an index column or not
Update_timeThe update time
Distinct_countThe distinct count
Null_countNULL count
Avg_col_sizeThe average col size
CorrelationPearson correlation coefficient between this column and the integer primary key column, indicating the degree of association between the two columns
Load_statusLoad status, such as allEvicted and allLoaded
Total_mem_usageThe total memory usage
Hist_mem_usageThe historical memory usage
Topn_mem_usageThe TopN memory usage
Cms_mem_usageThe CMS memory usage

Synopsis

ShowStatsHistogramsStmt ::=
    "SHOW" "STATS_HISTOGRAMS" ShowLikeOrWhere?

ShowLikeOrWhere ::=
    "LIKE" SimpleExpr
|   "WHERE" Expression

Examples

SHOW STATS_HISTOGRAMS;

+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
| Db_name | Table_name | Partition_name | Column_name | Is_index | Update_time         | Distinct_count | Null_count | Avg_col_size | Correlation |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
| test    | t          |                | a           |        0 | 2020-05-25 19:20:00 |              7 |          0 |            1 |           1 |
| test    | t2         |                | a           |        0 | 2020-05-25 19:20:01 |              6 |          0 |            8 |           0 |
| test    | t2         |                | b           |        0 | 2020-05-25 19:20:01 |              6 |          0 |         1.67 |           1 |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
3 rows in set (0.00 sec)

SHOW STATS_HISTOGRAMS WHERE table_name = 't2';

+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
| Db_name | Table_name | Partition_name | Column_name | Is_index | Update_time         | Distinct_count | Null_count | Avg_col_size | Correlation |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
| test    | t2         |                | b           |        0 | 2020-05-25 19:20:01 |              6 |          0 |         1.67 |           1 |
| test    | t2         |                | a           |        0 | 2020-05-25 19:20:01 |              6 |          0 |            8 |           0 |
+---------+------------+----------------+-------------+----------+---------------------+----------------+------------+--------------+-------------+
2 rows in set (0.00 sec)

MySQL compatibility

This statement is a TiDB extension to MySQL syntax.

See also