SHOW STATS_BUCKETS
SHOW STATS_BUCKETS
语句显示 统计信息 中的桶信息。
目前,SHOW STATS_BUCKETS
语句返回以下列:
列名 | 描述 |
---|---|
Db_name | 数据库名称 |
Table_name | 表名称 |
Partition_name | 分区名称 |
Column_name | 列名称(当 is_index 为 0 时)或索引名称(当 is_index 为 1 时) |
Is_index | 是否为索引列 |
Bucket_id | 桶的 ID |
Count | 落在该桶及之前桶中的所有值的数量 |
Repeats | 最大值的出现次数 |
Lower_bound | 最小值 |
Upper_bound | 最大值 |
Ndv | 桶中不同值的数量。该字段已废弃,由于其不准确,始终显示 0 。 |
概要
- ShowStatsBucketsStmt
- ShowLikeOrWhere
ShowStatsBucketsStmt ::=
"SHOW" "STATS_BUCKETS" ShowLikeOrWhere?
ShowLikeOrWhere ::=
"LIKE" SimpleExpr
| "WHERE" Expression
示例
SHOW STATS_BUCKETS WHERE Table_name='t';
+---------+------------+----------------+-------------+----------+-----------+-------+---------+--------------------------+--------------------------+------+
| Db_name | Table_name | Partition_name | Column_name | Is_index | Bucket_id | Count | Repeats | Lower_Bound | Upper_Bound | Ndv |
+---------+------------+----------------+-------------+----------+-----------+-------+---------+--------------------------+--------------------------+------+
| test | t | | a | 0 | 0 | 1 | 1 | 2023-12-27 00:00:00 | 2023-12-27 00:00:00 | 0 |
| test | t | | a | 0 | 1 | 2 | 1 | 2023-12-28 00:00:00 | 2023-12-28 00:00:00 | 0 |
| test | t | | ia | 1 | 0 | 1 | 1 | (NULL, 2) | (NULL, 2) | 0 |
| test | t | | ia | 1 | 1 | 2 | 1 | (NULL, 4) | (NULL, 4) | 0 |
| test | t | | ia | 1 | 2 | 3 | 1 | (2023-12-27 00:00:00, 1) | (2023-12-27 00:00:00, 1) | 0 |
| test | t | | ia | 1 | 3 | 4 | 1 | (2023-12-28 00:00:00, 3) | (2023-12-28 00:00:00, 3) | 0 |
+---------+------------+----------------+-------------+----------+-----------+-------+---------+--------------------------+--------------------------+------+
6 行结果(0.00 秒)
MySQL 兼容性
该语句是 TiDB 对 MySQL 语法的扩展。