cherry pick pingcap#19680 to release-3.0 (pingcap#19919)

ti-srebot · Sep 11, 2020 · d23d8bd · d23d8bd
1 parent 40a147c
commit d23d8bd
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Showing 3 changed files with 15 additions and 16 deletions.
diff --git a/executor/aggfuncs/builder.go b/executor/aggfuncs/builder.go
@@ -387,24 +387,20 @@ func buildVarPop(aggFuncDesc *aggregation.AggFuncDesc, ordinal int) AggFunc {
 
 // buildStdDevPop builds the AggFunc implementation for function "STD()/STDDEV()/STDDEV_POP()"
 func buildStdDevPop(aggFuncDesc *aggregation.AggFuncDesc, ordinal int) AggFunc {
-	base := baseStdDevPopAggFunc{
-		varPop4Float64{
-			baseVarPopAggFunc{
-				baseAggFunc{
-					args:    aggFuncDesc.Args,
-					ordinal: ordinal,
-				},
-			},
+	base := baseVarPopAggFunc{
+		baseAggFunc{
+			args:    aggFuncDesc.Args,
+			ordinal: ordinal,
 		},
 	}
 	switch aggFuncDesc.Mode {
 	case aggregation.DedupMode:
 		return nil
 	default:
 		if aggFuncDesc.HasDistinct {
-			return &stdDevPop4DistinctFloat64{base}
+			return &stdDevPop4DistinctFloat64{varPop4DistinctFloat64{base}}
 		}
-		return &stdDevPop4Float64{base}
+		return &stdDevPop4Float64{varPop4Float64{base}}
 	}
 }
 

diff --git a/executor/aggfuncs/func_stddevpop.go b/executor/aggfuncs/func_stddevpop.go
@@ -20,12 +20,8 @@ import (
 	"github.com/pingcap/tidb/util/chunk"
 )
 
-type baseStdDevPopAggFunc struct {
-	varPop4Float64
-}
-
 type stdDevPop4Float64 struct {
-	baseStdDevPopAggFunc
+	varPop4Float64
 }
 
 func (e *stdDevPop4Float64) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {
@@ -40,7 +36,7 @@ func (e *stdDevPop4Float64) AppendFinalResult2Chunk(sctx sessionctx.Context, pr
 }
 
 type stdDevPop4DistinctFloat64 struct {
-	baseStdDevPopAggFunc
+	varPop4DistinctFloat64
 }
 
 func (e *stdDevPop4DistinctFloat64) AppendFinalResult2Chunk(sctx sessionctx.Context, pr PartialResult, chk *chunk.Chunk) error {

diff --git a/executor/aggregate_test.go b/executor/aggregate_test.go
@@ -427,6 +427,13 @@ func (s *testSuite1) TestAggregation(c *C) {
 	tk.MustQuery("select  stddev_pop(b) from t1 group by a order by a;").Check(testkit.Rows("<nil>", "0", "0"))
 	tk.MustQuery("select  std(b) from t1 group by a order by a;").Check(testkit.Rows("<nil>", "0", "0"))
 	tk.MustQuery("select  stddev(b) from t1 group by a order by a;").Check(testkit.Rows("<nil>", "0", "0"))
+	// For issue #19676 The result of stddev_pop(distinct xxx) is wrong
+	tk.MustExec("drop table if exists t1;")
+	tk.MustExec("CREATE TABLE t1 (id int);")
+	tk.MustExec("insert into t1 values (1),(2);")
+	tk.MustQuery("select  stddev_pop(id) from t1;").Check(testkit.Rows("0.5"))
+	tk.MustExec("insert into t1 values (1);")
+	tk.MustQuery("select  stddev_pop(distinct id) from t1;").Check(testkit.Rows("0.5"))
 }
 
 func (s *testSuite1) TestStreamAggPushDown(c *C) {