mysql-test(filesort_merge) failed.

[wjhuang2016]

Bug Report

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1. Minimal reproduce step (Required)

https://ci.pingcap.net/blue/organizations/jenkins/tidb_ghpr_integration_common_test/detail/tidb_ghpr_integration_common_test/12349/pipeline

2. What did you expect to see? (Required)

3. What did you see instead (Required)

4. What is your TiDB version? (Required)

master

[Yisaer]

[2022/08/10 14:07:17.734 +08:00] [INFO] [handle.go:1189] ["[stats] directly update count"] [tableID=91] [results.Count=2373] [count=2373]
[2022/08/10 14:07:18.005 +08:00] [INFO] [analyze.go:426] ["analyze table `filesort_merge`.`t1` has finished"] [partition=] ["job info"="analyze table all columns with 256 buckets, 500 topn, 1 samplerate"] ["start time"=2022/08/10 14:07:17.715 +08:00] ["end time"=2022/08/10 14:07:17.980 +08:00] [cost=265.736394ms]
[2022/08/10 14:07:22.272 +08:00] [INFO] [manager.go:296] ["get owner"] ["owner info"="[log-backup] /tidb/br-stream/owner ownerManager e451b3b2-6623-4ab7-b4ae-754a5e9c9aa8"] [ownerID=e451b3b2-6623-4ab7-b4ae-754a5e9c9aa8]
[2022/08/10 14:07:26.845 +08:00] [INFO] [data_window.go:248] ["Error exists when getting the SQL Metric."]
[2022/08/10 14:07:32.551 +08:00] [INFO] [update.go:1133] ["[stats] auto analyze triggered"] [sql="analyze table `filesort_merge`.`t1`"] [reason="too many modifications(3072/2373>0.5)"]

From log we can find that 2373 is directly returned by analyze response Count from TiKV. A possibility root cause is about to txn isolation level.

The default isolation level is RC as following:

tidb/distsql/request_builder.go

Lines 160 to 171 in 8e77ce2

	// SetAnalyzeRequest sets the request type to "ReqTypeAnalyze" and construct request data.
	func (builder *RequestBuilder) SetAnalyzeRequest(ana *tipb.AnalyzeReq) *RequestBuilder {
	if builder.err == nil {
	builder.Request.Tp = kv.ReqTypeAnalyze
	builder.Request.Data, builder.err = ana.Marshal()
	builder.Request.NotFillCache = true
	builder.Request.IsolationLevel = kv.RC
	builder.Request.Priority = kv.PriorityLow
	}
	return builder
	}

and the testcase failed about 5 or 6 times once. After I changed it into SI, the testcase success 20 times in a row on my local env.

[Yisaer]

As the tikv analyze response returned wrong value, I transfer this issue into tikv/tikv#13258

[Yisaer]

I will close this issue as it seems we won't see this error in mysql-test now. Further information will be tracked in tikv/tikv#13258