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information-schema-tiflash-replica.md

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TIFLASH_REPLICA
Learn the `TIFLASH_REPLICA` information_schema table.

TIFLASH_REPLICA

The TIFLASH_REPLICA table provides information about TiFlash replicas available.

{{< copyable "sql" >}}

USE information_schema;
DESC tiflash_replica;
+-----------------+-------------+------+------+---------+-------+
| Field           | Type        | Null | Key  | Default | Extra |
+-----------------+-------------+------+------+---------+-------+
| TABLE_SCHEMA    | varchar(64) | YES  |      | NULL    |       |
| TABLE_NAME      | varchar(64) | YES  |      | NULL    |       |
| TABLE_ID        | bigint(21)  | YES  |      | NULL    |       |
| REPLICA_COUNT   | bigint(64)  | YES  |      | NULL    |       |
| LOCATION_LABELS | varchar(64) | YES  |      | NULL    |       |
| AVAILABLE       | tinyint(1)  | YES  |      | NULL    |       |
| PROGRESS        | double      | YES  |      | NULL    |       |
+-----------------+-------------+------+------+---------+-------+
7 rows in set (0.01 sec)

Fields in the TIFLASH_REPLICA table are described as follows:

  • TABLE_SCHEMA: the name of the database to which the table belongs.
  • TABLE_NAME: the name of the table.
  • TABLE_ID: the internal ID of the table, which is unique within a TiDB cluster.
  • REPLICA_COUNT: the number of TiFlash replicas.
  • LOCATION_LABELS: the LocationLabelList that is set when a TiFlash replica is created.
  • AVAILABLE: indicates whether the TiFlash replica of the table is available. When the value is 1 (available), the TiDB optimizer can intelligently choose to push down queries to TiKV or TiFlash based on query cost. When the value is 0 (unavailable), TiDB will not push down queries to TiFlash. Once the value of this field becomes 1 (available), it will not change anymore.
  • PROGRESS: the replication progress of TiFlash replicas, with the accuracy to two decimal places and at the minute level. The scope of this field is [0, 1]. When the AVAILABLE field is 1 and PROGRESS is less than 1, the TiFlash replica is far behind TiKV, and the queries pushed down to TiFlash will probably fail due to timeout of waiting for data replication.