executor: trace memory usage of ntile() (#19756)

executor/aggfuncs/aggfuncs.go

@@ -104,6 +104,8 @@ var (
 const (
 	// DefUint32Size is the size of uint32
 	DefUint32Size = int64(unsafe.Sizeof(uint32(0)))
+	// DefUint64Size is the size of uint64
+	DefUint64Size = int64(unsafe.Sizeof(uint64(0)))
 	// DefInt64Size is the size of int64
 	DefInt64Size = int64(unsafe.Sizeof(int64(0)))
 	// DefFloat64Size is the size of float64

executor/aggfuncs/func_ntile.go

@@ -14,10 +14,17 @@
 package aggfuncs
 
 import (
+	"unsafe"
+
 	"github.com/pingcap/tidb/sessionctx"
 	"github.com/pingcap/tidb/util/chunk"
 )
 
+const (
+	// DefPartialResult4Ntile is the size of partialResult4Ntile
+	DefPartialResult4Ntile = int64(unsafe.Sizeof(partialResult4Ntile{}))
+)
+
 // ntile divides the partition into n ranked groups and returns the group number a row belongs to.
 // e.g. We have 11 rows and n = 3. They will be divided into 3 groups.
 //      First 4 rows belongs to group 1. Following 4 rows belongs to group 2. The last 3 rows belongs to group 3.
@@ -35,7 +42,7 @@ type partialResult4Ntile struct {
 }
 
 func (n *ntile) AllocPartialResult() (pr PartialResult, memDelta int64) {
-	return PartialResult(&partialResult4Ntile{curGroupIdx: 1}), 0
+	return PartialResult(&partialResult4Ntile{curGroupIdx: 1}), DefPartialResult4Ntile
 }
 
 func (n *ntile) ResetPartialResult(pr PartialResult) {

executor/aggfuncs/func_ntile_test.go

@@ -0,0 +1,36 @@
+// Copyright 2020 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package aggfuncs_test
+
+import (
+	. "github.com/pingcap/check"
+	"github.com/pingcap/parser/ast"
+	"github.com/pingcap/parser/mysql"
+
+	"github.com/pingcap/tidb/executor/aggfuncs"
+)
+
+func (s *testSuite) TestMemNtile(c *C) {
+	tests := []windowMemTest{
+		buildWindowMemTester(ast.WindowFuncNtile, mysql.TypeLonglong, 1, 1, 1,
+			aggfuncs.DefPartialResult4Ntile, defaultUpdateMemDeltaGens),
+		buildWindowMemTester(ast.WindowFuncNtile, mysql.TypeLonglong, 1, 3, 0,
+			aggfuncs.DefPartialResult4Ntile, defaultUpdateMemDeltaGens),
+		buildWindowMemTester(ast.WindowFuncNtile, mysql.TypeLonglong, 1, 4, 1,
+			aggfuncs.DefPartialResult4Ntile, defaultUpdateMemDeltaGens),
+	}
+	for _, test := range tests {
+		s.testWindowAggMemFunc(c, test)
+	}
+}