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Merge remote-tracking branch 'upstream/master' into lock-view-sprint4
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TomShawn committed Aug 25, 2021
2 parents a638da5 + bd3500a commit 8851c2d
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8 changes: 4 additions & 4 deletions system-variables.md
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Expand Up @@ -321,16 +321,16 @@ MPP is a distributed computing framework provided by the TiFlash engine, which a

- Scope: SESSION | GLOBAL
- Default value: `10240`
- Range: `[-1, 9223372036854775807]`
- The unit of the variable is rows. If the objects of the join operation belong to a subquery, the optimizer cannot estimate the size of the subquery result set. In this situation, the size is determined by the number of rows in the result set. If the estimated number of rows in the subquery is less than the value of this variable, the Broadcast Hash Join algorithm is used. Otherwise, the Shuffled Hash Join algorithm is used. When `tidb_broadcast_join_threshold_count = -1`, the threshold is infinitely high.
- Range: `[0, 9223372036854775807]`
- The unit of the variable is rows. If the objects of the join operation belong to a subquery, the optimizer cannot estimate the size of the subquery result set. In this situation, the size is determined by the number of rows in the result set. If the estimated number of rows in the subquery is less than the value of this variable, the Broadcast Hash Join algorithm is used. Otherwise, the Shuffled Hash Join algorithm is used.

### tidb_broadcast_join_threshold_size <span class="version-mark">New in v5.0</span>

- Scope: SESSION | GLOBAL
- Default value: `104857600` (100 MiB)
- Range: `[-1, 9223372036854775807]`
- Range: `[0, 9223372036854775807]`
- Unit: Bytes
- If the table size is less than the value of the variable, the Broadcast Hash Join algorithm is used. Otherwise, the Shuffled Hash Join algorithm is used. When `tidb_broadcast_join_threshold_size = -1`, the threshold is infinitely high.
- If the table size is less than the value of the variable, the Broadcast Hash Join algorithm is used. Otherwise, the Shuffled Hash Join algorithm is used.

### tidb_build_stats_concurrency

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4 changes: 2 additions & 2 deletions tiflash/use-tiflash.md
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Expand Up @@ -353,8 +353,8 @@ In the example execution plan, the `ExchangeReceiver` and `ExchangeSender` opera
TiFlash provides the following two global/session variables to control whether to use Broadcast Hash Join:
- [`tidb_broadcast_join_threshold_size`](/system-variables.md#tidb_broadcast_join_threshold_count-new-in-v50): The unit of the value is bytes. If the table size (in the unit of bytes) is less than the value of the variable, the Broadcast Hash Join algorithm is used. Otherwise, the Shuffled Hash Join algorithm is used. When `tidb_broadcast_join_threshold_size = -1`, the threshold is infinitely high.
- [`tidb_broadcast_join_threshold_count`](/system-variables.md#tidb_broadcast_join_threshold_count-new-in-v50): The unit of the value is rows. If the objects of the join operation belong to a subquery, the optimizer cannot estimate the size of the subquery result set, so the size is determined by the number of rows in the result set. If the estimated number of rows in the subquery is less than the value of this variable, the Broadcast Hash Join algorithm is used. Otherwise, the Shuffled Hash Join algorithm is used. When `tidb_broadcast_join_threshold_count = -1`, the threshold is infinitely high.
- [`tidb_broadcast_join_threshold_size`](/system-variables.md#tidb_broadcast_join_threshold_count-new-in-v50): The unit of the value is bytes. If the table size (in the unit of bytes) is less than the value of the variable, the Broadcast Hash Join algorithm is used. Otherwise, the Shuffled Hash Join algorithm is used.
- [`tidb_broadcast_join_threshold_count`](/system-variables.md#tidb_broadcast_join_threshold_count-new-in-v50): The unit of the value is rows. If the objects of the join operation belong to a subquery, the optimizer cannot estimate the size of the subquery result set, so the size is determined by the number of rows in the result set. If the estimated number of rows in the subquery is less than the value of this variable, the Broadcast Hash Join algorithm is used. Otherwise, the Shuffled Hash Join algorithm is used.
## Notes
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2 changes: 1 addition & 1 deletion tikv-configuration-file.md
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Expand Up @@ -319,7 +319,7 @@ Configuration items related to the sharing of block cache among multiple RocksDB

## storage.flow-control

Configuration items related to the flow control mechanism in TiKV. This mechanism supersedes the write stall mechanism in RocksDB and controls flow at the scheduler layer, which avoids the issue of QPS drop caused by the stuck Raftstore or Apply threads when the write traffic is high.
Configuration items related to the flow control mechanism in TiKV. This mechanism replaces the write stall mechanism in RocksDB and controls flow at the scheduler layer, which avoids the issue of QPS drop caused by the stuck Raftstore or Apply threads when the write traffic is high.

### `enable`

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