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add new config hashagg_use_magic_hash for tiflash #19869

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add new config hashagg_use_magic_hash for tiflash #19869

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595424c
add new config hashagg_use_magic_hash for tiflash
guo-shaoge Feb 20, 2025
debfbce
update version
guo-shaoge Feb 28, 2025
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5 changes: 5 additions & 0 deletions tiflash/tiflash-configuration.md
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Expand Up @@ -265,6 +265,11 @@ delta_index_cache_size = 0
## 从 v6.4.0 引入，用于 MinTSO 调度器，表示一个 TiFlash 实例中最多可同时运行的查询数量，默认值为 0，即两倍的 vCPU 数量。关于 MinTSO 调度器，详见 https://docs.pingcap.com/zh/tidb/dev/tiflash-mintso-scheduler
task_scheduler_active_set_soft_limit = 0

## 从 v9.0.0 引入，如果该配置为 true，TiFlash 的 HashAgg 会使用 magic hash 而非默认的 CRC32。
## magic hash 的结果更加均匀，可以减少哈希冲突，但代价是计算速度比 CRC32 更慢。
## 作为调优手段，推荐在 GroupBy key 的 NDV 很高时打开该配置。
hashagg_use_magic_hash = false

## 安全相关配置，从 v4.0.5 开始生效
[security]
## 从 v5.0 引入，控制是否开启日志脱敏。可选值为 `true`、`false`、`"on"`、`"off"` 和 `"marker"`。其中，`"on"`、`"off"` 和 `"marker"` 从 v8.2.0 开始支持。
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