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Reverted: update bcj threshold #6875

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8 changes: 4 additions & 4 deletions system-variables.md
Original file line number Diff line number Diff line change
Expand Up @@ -328,16 +328,16 @@ MPP 是 TiFlash 引擎提供的分布式计算框架,允许节点之间的数

- 作用域:SESSION | GLOBAL
- 默认值:`10240`
- 范围:`[0, 9223372036854775807]`
- 单位为行数。如果 join 的对象为子查询,优化器无法估计子查询结果集大小,在这种情况下通过结果集行数判断。如果子查询的行数估计值小于该变量,则选择 Broadcast Hash Join 算法。否则选择 Shuffled Hash Join 算法。
- 范围:`[-1, 9223372036854775807]`
- 单位为行数。如果 join 的对象为子查询,优化器无法估计子查询结果集大小,在这种情况下通过结果集行数判断。如果子查询的行数估计值小于该变量,则选择 Broadcast Hash Join 算法。否则选择 Shuffled Hash Join 算法。当设置为 -1 时,代表无穷大。
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### `tidb_broadcast_join_threshold_size` <span class="version-mark">从 v5.0 版本开始引入</span>

- 作用域:SESSION | GLOBAL
- 默认值:`104857600` (100 MiB)
- 范围:`[0, 9223372036854775807]`
- 范围:`[-1, 9223372036854775807]`
- 单位:字节
- 如果表大小(字节数)小于该值,则选择 Broadcast Hash Join 算法。否则选择 Shuffled Hash Join 算法。
- 如果表大小(字节数)小于该值,则选择 Broadcast Hash Join 算法。否则选择 Shuffled Hash Join 算法。当设置为 -1 时,代表无穷大。
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### `tidb_build_stats_concurrency`

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4 changes: 2 additions & 2 deletions tiflash/use-tiflash.md
Original file line number Diff line number Diff line change
Expand Up @@ -347,8 +347,8 @@ mysql> explain select count(*) from customer c join nation n on c.c_nationkey=n.

TiFlash 提供了两个全局/会话变量决定是否选择 Broadcast Hash Join,分别为:

- [`tidb_broadcast_join_threshold_size`](/system-variables.md#tidb_broadcast_join_threshold_count-从-v50-版本开始引入),单位为 bytes。如果表大小(字节数)小于该值,则选择 Broadcast Hash Join 算法。否则选择 Shuffled Hash Join 算法。
- [`tidb_broadcast_join_threshold_count`](/system-variables.md#tidb_broadcast_join_threshold_count-从-v50-版本开始引入),单位为行数。如果 join 的对象为子查询,优化器无法估计子查询结果集大小,在这种情况下通过结果集行数判断。如果子查询的行数估计值小于该变量,则选择 Broadcast Hash Join 算法。否则选择 Shuffled Hash Join 算法。
- [`tidb_broadcast_join_threshold_size`](/system-variables.md#tidb_broadcast_join_threshold_count-从-v50-版本开始引入),单位为 bytes。如果表大小(字节数)小于该值,则选择 Broadcast Hash Join 算法。否则选择 Shuffled Hash Join 算法。当设置为 -1 时,代表无穷大。
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- [`tidb_broadcast_join_threshold_count`](/system-variables.md#tidb_broadcast_join_threshold_count-从-v50-版本开始引入),单位为行数。如果 join 的对象为子查询,优化器无法估计子查询结果集大小,在这种情况下通过结果集行数判断。如果子查询的行数估计值小于该变量,则选择 Broadcast Hash Join 算法。否则选择 Shuffled Hash Join 算法。当设置为 -1 时,代表无穷大。
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## 注意事项

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