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SHOW STATS_HISTOGRAMS
An overview of the usage of SHOW STATS_HISTOGRAMS for TiDB database.
/docs/dev/sql-statements/sql-statement-show-histograms/
/tidb/dev/sql-statement-show-histograms

SHOW STATS_HISTOGRAMS

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 name Description
Db_name Database name
Table_name The table name
Partition_name The partition name
Column_name The column name (when is_index is 0) or the index name (when is_index is 1)
Is_index Whether it is an index column or not
Update_time The update time
Distinct_count The distinct count
Null_count NULL count
Avg_col_size The average col size
Correlation Pearson correlation coefficient between this column and the integer primary key column, indicating the degree of association between the two columns
Load_status Load status, such as allEvicted and allLoaded
Total_mem_usage The total memory usage
Hist_mem_usage The historical memory usage
Topn_mem_usage The TopN memory usage
Cms_mem_usage The 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