FLUSH TABLES

FLUSH TABLES 语句用于提供 MySQL 兼容性，但在 TiDB 中并无有效用途。

语法图

FlushStmt ::=
    'FLUSH' NoWriteToBinLogAliasOpt FlushOption
NoWriteToBinLogAliasOpt ::=
    ( 'NO_WRITE_TO_BINLOG' | 'LOCAL' )?
FlushOption ::=
    'PRIVILEGES'
|   'STATUS'
|    'TIDB' 'PLUGINS' PluginNameList
|    'HOSTS'
|    LogTypeOpt 'LOGS'
|    TableOrTables TableNameListOpt WithReadLockOpt
LogTypeOpt ::=
    ( 'BINARY' | 'ENGINE' | 'ERROR' | 'GENERAL' | 'SLOW' )?
TableOrTables ::=
    'TABLE'
|   'TABLES'
TableNameListOpt ::=
    TableNameList?
WithReadLockOpt ::=
    ( 'WITH' 'READ' 'LOCK' )?

示例

FLUSH TABLES;

Query OK, 0 rows affected (0.00 sec)

FLUSH TABLES WITH READ LOCK;

ERROR 1105 (HY000): FLUSH TABLES WITH READ LOCK is not supported.  Please use @@tidb_snapshot

MySQL 兼容性

• TiDB 没有 MySQL 中的表缓存这一概念。所以，FLUSH TABLES 因 MySQL 兼容性会在 TiDB 中解析出但会被忽略掉。
• 因为 TiDB 目前不支持锁表，所以FLUSH TABLES WITH READ LOCK 语句会产生错误。建议使用 Historical reads 来实现锁表。

另请参阅

• Read historical data