empty region 持续上涨

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【TiDB 版本】v4.0.9
【问题描述】配置了merge region 相关的参数,但是监控中empty region 依然持续上涨

参数和监控图如下

概要

{
“replication”: {
“enable-placement-rules”: “true”,
“location-labels”: “host”,
“max-replicas”: 3,
“strictly-match-label”: “false”
},
“schedule”: {
“enable-cross-table-merge”: “false”,
“enable-debug-metrics”: “false”,
“enable-location-replacement”: “true”,
“enable-make-up-replica”: “true”,
“enable-one-way-merge”: “false”,
“enable-remove-down-replica”: “true”,
“enable-remove-extra-replica”: “true”,
“enable-replace-offline-replica”: “true”,
“high-space-ratio”: 0.7,
“hot-region-cache-hits-threshold”: 3,
“hot-region-schedule-limit”: 4,
“leader-schedule-limit”: 64,
“leader-schedule-policy”: “count”,
“low-space-ratio”: 0.8,
“max-merge-region-keys”: 200000,
“max-merge-region-size”: 20,
“max-pending-peer-count”: 16,
“max-snapshot-count”: 3,
“max-store-down-time”: “30m0s”,
“merge-schedule-limit”: 128,
“patrol-region-interval”: “50ms”,
“region-schedule-limit”: 4096,
“replica-schedule-limit”: 128,
“scheduler-max-waiting-operator”: 5,
“split-merge-interval”: “1h0m0s”,
“store-limit-mode”: “manual”,
“tolerant-size-ratio”: 0
}
}


我先修改下tikv 的一个参数看看 split-region-on-table

现在怎么样了?

:wink: 效果有点明显,主要是 config set enable-cross-table-merge true 得设置上。我给漏了

:+1::+1:

今天下午还遇到过这个情况。一个表就一行数据,count(*) 用了几十秒
我怀疑是空region 太多导致。因为上游会对这个表经常truncate 然后再导入数据。

下午合并了region 后,现在就瞬间返回。想确认下 是大量的空region 导致了 count(*) 一条数据慢么 ?

应该不会,下次遇到这种问题,可以保留一下当时 explain analyze 的结果,看下具体的耗时在什么阶段。