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reference/configuration: add tidb_row_format_version #2605

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Apr 8, 2020
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reference/configuration: add tidb_row_format_version #2605

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reference/configuration: add tidb_row_format_version
lysu Apr 1, 2020
b25320c
Update reference/configuration/tidb-server/tidb-specific-variables.md
lysu Apr 7, 2020
6fe932a
Merge branch 'master' into dev-add-row-format-var
jackysp Apr 8, 2020
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12 changes: 12 additions & 0 deletions reference/configuration/tidb-server/tidb-specific-variables.md
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Expand Up @@ -430,6 +430,18 @@ set @@global.tidb_distsql_scan_concurrency = 10;
- `CREATE TABLE`：`CREATE TABLE t (c int) SHARD_ROW_ID_BITS = 4;`
- `ALTER TABLE`：`ALTER TABLE t SHARD_ROW_ID_BITS = 4;`

### tidb_row_format_version

作用域：GLOBAL

默认值：2

控制新保存数据的表数据格式版本。TiDB v4.0 中默认使用版本号为 2 的[新表数据格式](https://github.com/pingcap/tidb/blob/master/docs/design/2018-07-19-row-format.md)保存新数据。

但如果从 4.0.0 之前的版本升级到 4.0.0, 不会改变表数据格式版本, TiDB 会继续使用版本为 1 的旧格式写入，即**只有新创建的集群才会默认使用新表数据格式**。
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需要注意的是修改该变量不会对已保存的老数据产生影响，只会对修改变量后的新写入数据使用对应版本格式保存。

### tidb_slow_log_threshold

作用域：SESSION
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