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
- ShowLikeOrWhere
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.