From 99dc72385244a38dbd1b8b880a3093d6cb8f00bd Mon Sep 17 00:00:00 2001
From: pingcap-github-bot <sre-bot@pingcap.com>
Date: Fri, 19 Jun 2020 18:14:29 +0800
Subject: [PATCH] session/statistics: discard feedbacks from `delete ...
 (#17452) (#17843)

---
 executor/builder.go              |  8 ++++----
 statistics/feedback.go           | 12 ++++++++----
 statistics/handle/update_test.go | 30 ++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 8 deletions(-)

diff --git a/executor/builder.go b/executor/builder.go
index f4d15fafceb32..341ee5f7ebafa 100644
--- a/executor/builder.go
+++ b/executor/builder.go
@@ -2274,7 +2274,7 @@ func buildNoRangeTableReader(b *executorBuilder, v *plannercore.PhysicalTableRea
 	} else {
 		e.feedback = statistics.NewQueryFeedback(getPhysicalTableID(tbl), ts.Hist, int64(ts.StatsCount()), ts.Desc)
 	}
-	collect := (b.ctx.GetSessionVars().StmtCtx.RuntimeStatsColl != nil) || e.feedback.CollectFeedback(len(ts.Ranges))
+	collect := statistics.CollectFeedback(b.ctx.GetSessionVars().StmtCtx, e.feedback, len(ts.Ranges))
 	if !collect {
 		e.feedback.Invalidate()
 	}
@@ -2357,7 +2357,7 @@ func buildNoRangeIndexReader(b *executorBuilder, v *plannercore.PhysicalIndexRea
 	} else {
 		e.feedback = statistics.NewQueryFeedback(e.physicalTableID, is.Hist, int64(is.StatsCount()), is.Desc)
 	}
-	collect := (b.ctx.GetSessionVars().StmtCtx.RuntimeStatsColl != nil) || e.feedback.CollectFeedback(len(is.Ranges))
+	collect := statistics.CollectFeedback(b.ctx.GetSessionVars().StmtCtx, e.feedback, len(is.Ranges))
 	if !collect {
 		e.feedback.Invalidate()
 	}
@@ -2460,10 +2460,10 @@ func buildNoRangeIndexLookUpReader(b *executorBuilder, v *plannercore.PhysicalIn
 	} else {
 		e.feedback = statistics.NewQueryFeedback(getPhysicalTableID(tbl), is.Hist, int64(is.StatsCount()), is.Desc)
 	}
-	// do not collect the feedback for table request.
+	// Do not collect the feedback for table request.
 	collectTable := false
 	e.tableRequest.CollectRangeCounts = &collectTable
-	collectIndex := (b.ctx.GetSessionVars().StmtCtx.RuntimeStatsColl != nil) || e.feedback.CollectFeedback(len(is.Ranges))
+	collectIndex := statistics.CollectFeedback(b.ctx.GetSessionVars().StmtCtx, e.feedback, len(is.Ranges))
 	if !collectIndex {
 		e.feedback.Invalidate()
 	}
diff --git a/statistics/feedback.go b/statistics/feedback.go
index 9773fd206d6d8..974cf121f3000 100644
--- a/statistics/feedback.go
+++ b/statistics/feedback.go
@@ -98,10 +98,14 @@ func (q *QueryFeedback) CalcErrorRate() float64 {
 }
 
 // CollectFeedback decides whether to collect the feedback. It returns false when:
-// 1: the histogram is nil or has no buckets;
-// 2: the number of scan ranges exceeds the limit because it may affect the performance;
-// 3: it does not pass the probabilistic sampler.
-func (q *QueryFeedback) CollectFeedback(numOfRanges int) bool {
+// 1: the feedback is not generated by select query;
+// 2: the histogram is nil or has no buckets;
+// 3: the number of scan ranges exceeds the limit because it may affect the performance;
+// 4: it does not pass the probabilistic sampler.
+func CollectFeedback(sc *stmtctx.StatementContext, q *QueryFeedback, numOfRanges int) bool {
+	if !sc.InSelectStmt {
+		return false
+	}
 	if q.Hist == nil || q.Hist.Len() == 0 {
 		return false
 	}
diff --git a/statistics/handle/update_test.go b/statistics/handle/update_test.go
index 8109f932bd801..6bd2139afc35c 100644
--- a/statistics/handle/update_test.go
+++ b/statistics/handle/update_test.go
@@ -1674,3 +1674,33 @@ func (s *testStatsSuite) TestLoadHistCorrelation(c *C) {
 	c.Assert(len(result.Rows()), Equals, 1)
 	c.Assert(result.Rows()[0][9], Equals, "1")
 }
+
+func (s *testStatsSuite) TestDeleteUpdateFeedback(c *C) {
+	defer cleanEnv(c, s.store, s.do)
+	testKit := testkit.NewTestKit(c, s.store)
+
+	oriProbability := statistics.FeedbackProbability
+	defer func() {
+		statistics.FeedbackProbability = oriProbability
+	}()
+	statistics.FeedbackProbability.Store(1)
+
+	h := s.do.StatsHandle()
+	testKit.MustExec("use test")
+	testKit.MustExec("create table t (a bigint(64), b bigint(64), index idx_ab(a,b))")
+	for i := 0; i < 20; i++ {
+		testKit.MustExec(fmt.Sprintf("insert into t values (%d, %d)", i/5, i))
+	}
+	c.Assert(h.DumpStatsDeltaToKV(handle.DumpAll), IsNil)
+	testKit.MustExec("analyze table t with 3 buckets")
+
+	testKit.MustExec("delete from t where a = 1")
+	c.Assert(h.DumpStatsDeltaToKV(handle.DumpAll), IsNil)
+	c.Assert(len(h.GetQueryFeedback()), Equals, 0)
+	testKit.MustExec("update t set a = 6 where a = 2")
+	c.Assert(h.DumpStatsDeltaToKV(handle.DumpAll), IsNil)
+	c.Assert(len(h.GetQueryFeedback()), Equals, 0)
+	testKit.MustExec("explain analyze delete from t where a = 3")
+	c.Assert(h.DumpStatsDeltaToKV(handle.DumpAll), IsNil)
+	c.Assert(len(h.GetQueryFeedback()), Equals, 0)
+}