statistics: fix the correlation estimation for version 2 (#23057)

pingcap · Mar 3, 2021 · a4b4d7a · a4b4d7a
1 parent b5582e0
commit a4b4d7a
Show file tree

Hide file tree

Showing 2 changed files with 23 additions and 1 deletion.
diff --git a/statistics/builder.go b/statistics/builder.go
@@ -285,6 +285,9 @@ func BuildColumnHistAndTopN(ctx sessionctx.Context, numBuckets, numTopN int, id
 		cur, curCnt = sampleBytes, 1
 	}
 
+	// Calc the correlation of the column between the handle column.
+	hg.Correlation = calcCorrelation(sampleNum, corrXYSum)
+
 	// Handle the counting for the last value. Basically equal to the case 2 above.
 	// now topn is empty: append the "current" count directly
 	if len(topNList) == 0 {
@@ -340,6 +343,5 @@ func BuildColumnHistAndTopN(ctx sessionctx.Context, numBuckets, numTopN int, id
 		}
 	}
 
-	hg.Correlation = calcCorrelation(int64(len(samples)), corrXYSum)
 	return hg, topn, nil
 }
diff --git a/statistics/handle/handle_test.go b/statistics/handle/handle_test.go
@@ -621,8 +621,15 @@ func (s *testStatsSuite) TestCorrelation(c *C) {
 	c.Assert(len(result.Rows()), Equals, 2)
 	c.Assert(result.Rows()[0][9], Equals, "0")
 	c.Assert(result.Rows()[1][9], Equals, "0.8285714285714286")
+	testKit.MustExec("set @@session.tidb_analyze_version=2")
+	testKit.MustExec("analyze table t")
+	result = testKit.MustQuery("show stats_histograms where Table_name = 't'").Sort()
+	c.Assert(len(result.Rows()), Equals, 2)
+	c.Assert(result.Rows()[0][9], Equals, "0")
+	c.Assert(result.Rows()[1][9], Equals, "0.8285714285714286")
 
 	testKit.MustExec("truncate table t")
+	testKit.MustExec("set @@session.tidb_analyze_version=1")
 	result = testKit.MustQuery("show stats_histograms where Table_name = 't'").Sort()
 	c.Assert(len(result.Rows()), Equals, 0)
 	testKit.MustExec("insert into t values(1,21),(3,12),(4,7),(2,20),(5,1)")
@@ -637,8 +644,15 @@ func (s *testStatsSuite) TestCorrelation(c *C) {
 	c.Assert(len(result.Rows()), Equals, 2)
 	c.Assert(result.Rows()[0][9], Equals, "0")
 	c.Assert(result.Rows()[1][9], Equals, "-0.9428571428571428")
+	testKit.MustExec("set @@session.tidb_analyze_version=2")
+	testKit.MustExec("analyze table t")
+	result = testKit.MustQuery("show stats_histograms where Table_name = 't'").Sort()
+	c.Assert(len(result.Rows()), Equals, 2)
+	c.Assert(result.Rows()[0][9], Equals, "0")
+	c.Assert(result.Rows()[1][9], Equals, "-0.9428571428571428")
 
 	testKit.MustExec("truncate table t")
+	testKit.MustExec("set @@session.tidb_analyze_version=1")
 	testKit.MustExec("insert into t values (1,1),(2,1),(3,1),(4,1),(5,1),(6,1),(7,1),(8,1),(9,1),(10,1),(11,1),(12,1),(13,1),(14,1),(15,1),(16,1),(17,1),(18,1),(19,1),(20,2),(21,2),(22,2),(23,2),(24,2),(25,2)")
 	testKit.MustExec("analyze table t")
 	result = testKit.MustQuery("show stats_histograms where Table_name = 't'").Sort()
@@ -654,6 +668,12 @@ func (s *testStatsSuite) TestCorrelation(c *C) {
 	c.Assert(len(result.Rows()), Equals, 2)
 	c.Assert(result.Rows()[0][9], Equals, "1")
 	c.Assert(result.Rows()[1][9], Equals, "0.8285714285714286")
+	testKit.MustExec("set @@session.tidb_analyze_version=2")
+	testKit.MustExec("analyze table t")
+	result = testKit.MustQuery("show stats_histograms where Table_name = 't'").Sort()
+	c.Assert(len(result.Rows()), Equals, 2)
+	c.Assert(result.Rows()[0][9], Equals, "1")
+	c.Assert(result.Rows()[1][9], Equals, "0.8285714285714286")
 
 	testKit.MustExec("truncate table t")
 	testKit.MustExec("insert into t values(1,1),(2,7),(3,12),(8,18),(4,20),(5,21)")