*: support automatically create sql baselines #12434

alivxxx · 2019-09-27T05:51:03Z

What problem does this PR solve?

Support automatically capture sql baselines.

What is changed and how it works?

This PR uses a background job to loop over the statements summary to find selects that occured more than once and add sql bindings for them. The backgroud job can be controlled by variable "tidb_capture_plan_baselines", and since this feature relys on statements, "tidb_enable_stmt_summary" should also be set in order to enable the feature.

Check List

Tests

Unit test

Code changes

Has exported function/method change

Side effects

None

Related changes

None

Release note

support automatically capture sql baselines

codecov · 2019-09-27T05:58:07Z

Codecov Report

Merging #12434 into master will increase coverage by 0.2428%.
The diff coverage is n/a.

@@               Coverage Diff                @@
##             master     #12434        +/-   ##
================================================
+ Coverage   80.0043%   80.2471%   +0.2428%     
================================================
  Files           462        462                
  Lines        106273     107301      +1028     
================================================
+ Hits          85023      86106      +1083     
+ Misses        14938      14892        -46     
+ Partials       6312       6303         -9

winoros

lgtm
Is there some TP type benchmark result to show its influence?

alivxxx · 2019-10-10T11:22:32Z

/bench

sre-bot · 2019-10-10T13:47:43Z

@@                               Benchmark Diff                               @@
================================================================================
--- tidb: 8392e1be6b15b0e276356e9d02517ab08945a637
+++ tidb: 7700dab95cc4f6c943e525ecdf50f6830b2277f7
tikv: e231d45170f2efeddf855c81b6f90d2a7f094d1b
pd: 4acaa8c715d40a07f521dd85ef7dcd4118064289
================================================================================
test-1: < oltp_point_select >
    * QPS : 78243.60 ± 1.9166% (std=1049.51) delta: -0.72% (p=0.505)
    * AvgMs : 3.27 ± 1.8349% (std=0.04) delta: 1.40%
    * PercentileMs99 : 6.74 ± 1.0679% (std=0.06) delta: 1.08%
            
test-2: < oltp_read_write >
    * QPS : 37395.25 ± 0.4093% (std=89.09) delta: -2.23% (p=0.002)
    * AvgMs : 137.40 ± 0.4731% (std=0.40) delta: 2.41%
    * PercentileMs99 : 267.41 ± 0.0000% (std=0.00) delta: 3.67%
            
test-3: < oltp_insert >
    * QPS : 22192.97 ± 0.9017% (std=143.59) delta: -0.18% (p=0.950)
    * AvgMs : 11.53 ± 0.8848% (std=0.08) delta: 0.18%
    * PercentileMs99 : 23.27 ± 1.0830% (std=0.21) delta: -1.07%
            
test-4: < oltp_update_index >
    * QPS : 17394.34 ± 0.5992% (std=75.64) delta: -2.18% (p=0.000)
    * AvgMs : 14.71 ± 0.6524% (std=0.07) delta: 2.31%
    * PercentileMs99 : 30.59 ± 1.0788% (std=0.27) delta: -2.49%
            
test-5: < oltp_update_non_index >
    * QPS : 29210.34 ± 0.0594% (std=12.36) delta: -2.49% (p=0.000)
    * AvgMs : 8.76 ± 0.0000% (std=0.00) delta: 2.55%
    * PercentileMs99 : 18.95 ± 0.0000% (std=0.00) delta: -10.23%

https://perf.pingcap.com

This reverts commit 7700dab.

alivxxx · 2019-10-11T03:31:16Z

@winoros You can take a look at the bench result.

domain/domain.go

eurekaka · 2019-10-16T07:50:45Z

domain/domain.go

-		defer recoverInDomain("loadBindInfoLoop", false)
+		defer recoverInDomain("globalBindHandleWorkerLoop", false)
+		loadTicker := time.NewTicker(bindinfo.Lease)
+		captureBaselineTicker := time.NewTicker(bindinfo.Lease)


Can we just use a single ticker for 2 actions?

Oh, we can.

eurekaka · 2019-10-16T07:57:26Z

domain/global_vars_cache.go

 			stmtsummary.StmtSummaryByDigestMap.SetEnabled(sVal, false)
-			break
+		case variable.TiDBCapturePlanBaseline:


Shall we add dependency check between these 2 variables? if not, would there be possible panics when accessing structures of statements?

No, it won't panic because the StmtSummaryByDigestMap is initilized as a global variable, so it is always valid.

eurekaka · 2019-10-16T07:58:09Z

bindinfo/handle.go

+			continue
+		}
+		h.sctx.Lock()
+		err = h.sctx.RefreshTxnCtx(context.TODO())


Why do we need this function call?

It will create a new txn and the txn maybe used by the optimizer when generating hints, since it may execute some sub queries, and without it, the test will panic.

lzmhhh123 · 2019-10-16T09:40:55Z

sessionctx/variable/varsutil.go

+
+// GetVal gets the value.
+func (v *serverGlobalVariable) GetVal() string {
+	v.Lock()


Can we just set read lock here?

I think it is not necessary because we do not expect the server global variables be set or read very frequent, a mutex is enough now.

lzmhhh123 · 2019-10-16T09:44:43Z

util/stmtsummary/statement_summary.go

@@ -230,6 +230,26 @@ func (ssMap *stmtSummaryByDigestMap) ToDatum() [][]types.Datum {
 	return rows
 }

+// GetMoreThanOnceSelect gets select SQLs that occurred more than once.
+func (ssMap *stmtSummaryByDigestMap) GetMoreThanOnceSelect() ([]string, []string) {
+	ssMap.Lock()


It is a mutex, not rwmutex.

lzmhhh123 · 2019-10-16T09:52:17Z

util/stmtsummary/statement_summary.go

+	for _, value := range values {
+		summary := value.(*stmtSummaryByDigest)
+		summary.Lock()
+		if strings.HasPrefix(summary.normalizedSQL, "select") && summary.execCount > 1 {


Out of curiosity, can we make the SQL occurrent number under control instead of 1?

I guess we can, but we can do it when only when it is necessary because doing it would require another session variables, for now, it is enough.

lzmhhh123

LGTM

sre-bot · 2019-10-17T05:00:21Z

/run-all-tests

alivxxx · 2019-10-17T05:59:23Z

/run-all-tests

*: support automatically create sql baselines

9139d41

alivxxx added type/new-feature type/usability labels Sep 27, 2019

alivxxx requested review from eurekaka, winoros and lzmhhh123 September 27, 2019 05:51

winoros reviewed Oct 10, 2019

View reviewed changes

enable for test

7700dab

alivxxx added 3 commits October 11, 2019 10:54

Revert "enable for test"

dbe8335

This reverts commit 7700dab.

Merge branch 'master' of github.com:pingcap/tidb into capture-baseline

89ad543

add error check

a09ec75

lzmhhh123 reviewed Oct 11, 2019

View reviewed changes

domain/domain.go Outdated Show resolved Hide resolved

merge defer

6f5ec11

alivxxx requested a review from lzmhhh123 October 11, 2019 07:20

Merge branch 'master' of github.com:pingcap/tidb into capture-baseline

e8d9aa9

alivxxx force-pushed the capture-baseline branch from 91d5d42 to e8d9aa9 Compare October 15, 2019 08:23

eurekaka reviewed Oct 16, 2019

View reviewed changes

address comment

8cf72ec

lzmhhh123 reviewed Oct 16, 2019

View reviewed changes

lzmhhh123 approved these changes Oct 17, 2019

View reviewed changes

alivxxx added the status/can-merge Indicates a PR has been approved by a committer. label Oct 17, 2019

Merge branch 'master' into capture-baseline

84f1a88

Merge branch 'master' into capture-baseline

f585216

Merge branch 'master' into capture-baseline

62e7370

alivxxx added the status/all tests passed label Oct 17, 2019

alivxxx merged commit 740b776 into pingcap:master Oct 17, 2019

alivxxx deleted the capture-baseline branch October 17, 2019 06:16

XiaTianliang pushed a commit to XiaTianliang/tidb that referenced this pull request Dec 21, 2019

*: support automatically create sql baselines (pingcap#12434)

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*: support automatically create sql baselines #12434

*: support automatically create sql baselines #12434

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alivxxx commented Sep 27, 2019

What problem does this PR solve?

What is changed and how it works?

Check List

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