diff --git a/executor/aggregate.go b/executor/aggregate.go
index d89a04073ee37..bcba95859299d 100644
--- a/executor/aggregate.go
+++ b/executor/aggregate.go
@@ -51,15 +51,33 @@ type baseHashAggWorker struct {
 	aggFuncs     []aggfuncs.AggFunc
 	maxChunkSize int
 	stats        *AggWorkerStat
+
+	memTracker *memory.Tracker
+	BInMap     int // indicate there are 2^BInMap buckets in Golang Map.
 }
 
-func newBaseHashAggWorker(ctx sessionctx.Context, finishCh <-chan struct{}, aggFuncs []aggfuncs.AggFunc, maxChunkSize int) baseHashAggWorker {
-	return baseHashAggWorker{
+const (
+	// ref https://github.com/golang/go/blob/go1.15.6/src/reflect/type.go#L2162.
+	// defBucketMemoryUsage = bucketSize*(1+unsafe.Sizeof(string) + unsafe.Sizeof(slice))+2*ptrSize
+	// The bucket size may be changed by golang implement in the future.
+	defBucketMemoryUsage = 8*(1+16+24) + 16
+	// Maximum average load of a bucket that triggers growth is 6.5.
+	// Represent as loadFactorNum/loadFactDen, to allow integer math.
+	loadFactorNum = 13
+	loadFactorDen = 2
+)
+
+func newBaseHashAggWorker(ctx sessionctx.Context, finishCh <-chan struct{}, aggFuncs []aggfuncs.AggFunc,
+	maxChunkSize int, memTrack *memory.Tracker) baseHashAggWorker {
+	baseWorker := baseHashAggWorker{
 		ctx:          ctx,
 		finishCh:     finishCh,
 		aggFuncs:     aggFuncs,
 		maxChunkSize: maxChunkSize,
+		memTracker:   memTrack,
+		BInMap:       0,
 	}
+	return baseWorker
 }
 
 // HashAggPartialWorker indicates the partial workers of parallel hash agg execution,
@@ -76,8 +94,7 @@ type HashAggPartialWorker struct {
 	groupKey          [][]byte
 	// chk stores the input data from child,
 	// and is reused by childExec and partial worker.
-	chk        *chunk.Chunk
-	memTracker *memory.Tracker
+	chk *chunk.Chunk
 }
 
 // HashAggFinalWorker indicates the final workers of parallel hash agg execution,
@@ -296,7 +313,7 @@ func (e *HashAggExec) initForParallelExec(ctx sessionctx.Context) {
 	// Init partial workers.
 	for i := 0; i < partialConcurrency; i++ {
 		w := HashAggPartialWorker{
-			baseHashAggWorker: newBaseHashAggWorker(e.ctx, e.finishCh, e.PartialAggFuncs, e.maxChunkSize),
+			baseHashAggWorker: newBaseHashAggWorker(e.ctx, e.finishCh, e.PartialAggFuncs, e.maxChunkSize, e.memTracker),
 			inputCh:           e.partialInputChs[i],
 			outputChs:         e.partialOutputChs,
 			giveBackCh:        e.inputCh,
@@ -305,8 +322,9 @@ func (e *HashAggExec) initForParallelExec(ctx sessionctx.Context) {
 			groupByItems:      e.GroupByItems,
 			chk:               newFirstChunk(e.children[0]),
 			groupKey:          make([][]byte, 0, 8),
-			memTracker:        e.memTracker,
 		}
+		// There is a bucket in the empty partialResultsMap.
+		e.memTracker.Consume(defBucketMemoryUsage * (1 << w.BInMap))
 		if e.stats != nil {
 			w.stats = &AggWorkerStat{}
 			e.stats.PartialStats = append(e.stats.PartialStats, w.stats)
@@ -324,7 +342,7 @@ func (e *HashAggExec) initForParallelExec(ctx sessionctx.Context) {
 	// Init final workers.
 	for i := 0; i < finalConcurrency; i++ {
 		w := HashAggFinalWorker{
-			baseHashAggWorker:   newBaseHashAggWorker(e.ctx, e.finishCh, e.FinalAggFuncs, e.maxChunkSize),
+			baseHashAggWorker:   newBaseHashAggWorker(e.ctx, e.finishCh, e.FinalAggFuncs, e.maxChunkSize, e.memTracker),
 			partialResultMap:    make(aggPartialResultMapper),
 			groupSet:            set.NewStringSet(),
 			inputCh:             e.partialOutputChs[i],
@@ -334,6 +352,8 @@ func (e *HashAggExec) initForParallelExec(ctx sessionctx.Context) {
 			mutableRow:          chunk.MutRowFromTypes(retTypes(e)),
 			groupKeys:           make([][]byte, 0, 8),
 		}
+		// There is a bucket in the empty partialResultsMap.
+		e.memTracker.Consume(defBucketMemoryUsage * (1 << w.BInMap))
 		if e.stats != nil {
 			w.stats = &AggWorkerStat{}
 			e.stats.FinalStats = append(e.stats.FinalStats, w.stats)
@@ -406,8 +426,19 @@ func (w *HashAggPartialWorker) run(ctx sessionctx.Context, waitGroup *sync.WaitG
 	}
 }
 
+func getGroupKeyMemUsage(groupKey [][]byte) int64 {
+	mem := int64(0)
+	for _, key := range groupKey {
+		mem += int64(cap(key))
+	}
+	mem += 12 * int64(cap(groupKey))
+	return mem
+}
+
 func (w *HashAggPartialWorker) updatePartialResult(ctx sessionctx.Context, sc *stmtctx.StatementContext, chk *chunk.Chunk, finalConcurrency int) (err error) {
+	memSize := getGroupKeyMemUsage(w.groupKey)
 	w.groupKey, err = getGroupKey(w.ctx, chk, w.groupKey, w.groupByItems)
+	w.memTracker.Consume(getGroupKeyMemUsage(w.groupKey) - memSize)
 	if err != nil {
 		return err
 	}
@@ -418,9 +449,11 @@ func (w *HashAggPartialWorker) updatePartialResult(ctx sessionctx.Context, sc *s
 	for i := 0; i < numRows; i++ {
 		for j, af := range w.aggFuncs {
 			rows[0] = chk.GetRow(i)
-			if _, err := af.UpdatePartialResult(ctx, rows, partialResults[i][j]); err != nil {
+			memDelta, err := af.UpdatePartialResult(ctx, rows, partialResults[i][j])
+			if err != nil {
 				return err
 			}
+			w.memTracker.Consume(memDelta)
 		}
 	}
 	return nil
@@ -487,7 +520,7 @@ func getGroupKey(ctx sessionctx.Context, input *chunk.Chunk, groupKey [][]byte,
 	return groupKey, nil
 }
 
-func (w baseHashAggWorker) getPartialResult(sc *stmtctx.StatementContext, groupKey [][]byte, mapper aggPartialResultMapper) [][]aggfuncs.PartialResult {
+func (w *baseHashAggWorker) getPartialResult(sc *stmtctx.StatementContext, groupKey [][]byte, mapper aggPartialResultMapper) [][]aggfuncs.PartialResult {
 	n := len(groupKey)
 	partialResults := make([][]aggfuncs.PartialResult, n)
 	for i := 0; i < n; i++ {
@@ -496,10 +529,17 @@ func (w baseHashAggWorker) getPartialResult(sc *stmtctx.StatementContext, groupK
 			continue
 		}
 		for _, af := range w.aggFuncs {
-			partialResult, _ := af.AllocPartialResult()
+			partialResult, memDelta := af.AllocPartialResult()
 			partialResults[i] = append(partialResults[i], partialResult)
+			w.memTracker.Consume(memDelta)
 		}
 		mapper[string(groupKey[i])] = partialResults[i]
+		w.memTracker.Consume(int64(len(groupKey[i])))
+		// Map will expand when count > bucketNum * loadFactor. The memory usage will doubled.
+		if len(mapper) > (1<<w.BInMap)*loadFactorNum/loadFactorDen {
+			w.memTracker.Consume(defBucketMemoryUsage * (1 << w.BInMap))
+			w.BInMap++
+		}
 	}
 	return partialResults
 }
@@ -541,10 +581,12 @@ func (w *HashAggFinalWorker) consumeIntermData(sctx sessionctx.Context) (err err
 		for reachEnd := false; !reachEnd; {
 			intermDataBuffer, groupKeys, reachEnd = input.getPartialResultBatch(sc, intermDataBuffer[:0], w.aggFuncs, w.maxChunkSize)
 			groupKeysLen := len(groupKeys)
+			memSize := getGroupKeyMemUsage(w.groupKeys)
 			w.groupKeys = w.groupKeys[:0]
 			for i := 0; i < groupKeysLen; i++ {
 				w.groupKeys = append(w.groupKeys, []byte(groupKeys[i]))
 			}
+			w.memTracker.Consume(getGroupKeyMemUsage(w.groupKeys) - memSize)
 			finalPartialResults := w.getPartialResult(sc, w.groupKeys, w.partialResultMap)
 			for i, groupKey := range groupKeys {
 				if !w.groupSet.Exist(groupKey) {
@@ -575,10 +617,12 @@ func (w *HashAggFinalWorker) getFinalResult(sctx sessionctx.Context) {
 		return
 	}
 	execStart := time.Now()
+	memSize := getGroupKeyMemUsage(w.groupKeys)
 	w.groupKeys = w.groupKeys[:0]
 	for groupKey := range w.groupSet {
 		w.groupKeys = append(w.groupKeys, []byte(groupKey))
 	}
+	w.memTracker.Consume(getGroupKeyMemUsage(w.groupKeys) - memSize)
 	partialResults := w.getPartialResult(sctx.GetSessionVars().StmtCtx, w.groupKeys, w.partialResultMap)
 	for i := 0; i < len(w.groupSet); i++ {
 		for j, af := range w.aggFuncs {
diff --git a/executor/benchmark_test.go b/executor/benchmark_test.go
index fcabecc32e01b..90b798f422094 100644
--- a/executor/benchmark_test.go
+++ b/executor/benchmark_test.go
@@ -21,6 +21,7 @@ import (
 	"math/rand"
 	"os"
 	"sort"
+	"strconv"
 	"strings"
 	"sync"
 	"testing"
@@ -29,6 +30,7 @@ import (
 	"github.com/pingcap/log"
 	"github.com/pingcap/parser/ast"
 	"github.com/pingcap/parser/mysql"
+	"github.com/pingcap/tidb/executor/aggfuncs"
 	"github.com/pingcap/tidb/expression"
 	"github.com/pingcap/tidb/expression/aggregation"
 	"github.com/pingcap/tidb/planner/core"
@@ -2016,3 +2018,58 @@ func BenchmarkReadLastLinesOfHugeLine(b *testing.B) {
 		}
 	}
 }
+
+func BenchmarkAggPartialResultMapperMemoryUsage(b *testing.B) {
+	b.ReportAllocs()
+	type testCase struct {
+		rowNum    int
+		expectedB int
+	}
+	cases := []testCase{
+		{
+			rowNum:    0,
+			expectedB: 0,
+		},
+		{
+			rowNum:    100,
+			expectedB: 4,
+		},
+		{
+			rowNum:    10000,
+			expectedB: 11,
+		},
+		{
+			rowNum:    1000000,
+			expectedB: 18,
+		},
+		{
+			rowNum:    851968, // 6.5 * (1 << 17)
+			expectedB: 17,
+		},
+		{
+			rowNum:    851969, // 6.5 * (1 << 17) + 1
+			expectedB: 18,
+		},
+		{
+			rowNum:    425984, // 6.5 * (1 << 16)
+			expectedB: 16,
+		},
+		{
+			rowNum:    425985, // 6.5 * (1 << 16) + 1
+			expectedB: 17,
+		},
+	}
+
+	for _, c := range cases {
+		b.Run(fmt.Sprintf("MapRows %v", c.rowNum), func(b *testing.B) {
+			b.ReportAllocs()
+			for i := 0; i < b.N; i++ {
+				aggMap := make(aggPartialResultMapper)
+				tempSlice := make([]aggfuncs.PartialResult, 10)
+				for num := 0; num < c.rowNum; num++ {
+					aggMap[strconv.Itoa(num)] = tempSlice
+				}
+			}
+		})
+	}
+}
diff --git a/executor/executor_pkg_test.go b/executor/executor_pkg_test.go
index 75868833ede04..224512ccf93f9 100644
--- a/executor/executor_pkg_test.go
+++ b/executor/executor_pkg_test.go
@@ -16,7 +16,10 @@ package executor
 import (
 	"context"
 	"crypto/tls"
+	"runtime"
+	"strconv"
 	"time"
+	"unsafe"
 
 	. "github.com/pingcap/check"
 	"github.com/pingcap/failpoint"
@@ -24,6 +27,7 @@ import (
 	"github.com/pingcap/parser/auth"
 	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/tidb/config"
+	"github.com/pingcap/tidb/executor/aggfuncs"
 	"github.com/pingcap/tidb/expression"
 	plannerutil "github.com/pingcap/tidb/planner/util"
 	"github.com/pingcap/tidb/sessionctx/variable"
@@ -446,3 +450,133 @@ func (s *pkgTestSuite) TestSlowQueryRuntimeStats(c *C) {
 	stats.Merge(stats.Clone())
 	c.Assert(stats.String(), Equals, "initialize: 2ms, read_file: 2s, parse_log: {time:200ms, concurrency:15}, total_file: 4, read_file: 4, read_size: 2 GB")
 }
+
+// Test whether the actual buckets in Golang Map is same with the estimated number.
+// The test relies the implement of Golang Map. ref https://github.com/golang/go/blob/go1.13/src/runtime/map.go#L114
+func (s *pkgTestSuite) TestAggPartialResultMapperB(c *C) {
+	if runtime.Version() < `go1.13` {
+		c.Skip("Unsupported version")
+	}
+	type testCase struct {
+		rowNum          int
+		expectedB       int
+		expectedGrowing bool
+	}
+	cases := []testCase{
+		{
+			rowNum:          0,
+			expectedB:       0,
+			expectedGrowing: false,
+		},
+		{
+			rowNum:          100,
+			expectedB:       4,
+			expectedGrowing: false,
+		},
+		{
+			rowNum:          10000,
+			expectedB:       11,
+			expectedGrowing: false,
+		},
+		{
+			rowNum:          1000000,
+			expectedB:       18,
+			expectedGrowing: false,
+		},
+		{
+			rowNum:          851968, // 6.5 * (1 << 17)
+			expectedB:       17,
+			expectedGrowing: false,
+		},
+		{
+			rowNum:          851969, // 6.5 * (1 << 17) + 1
+			expectedB:       18,
+			expectedGrowing: true,
+		},
+		{
+			rowNum:          425984, // 6.5 * (1 << 16)
+			expectedB:       16,
+			expectedGrowing: false,
+		},
+		{
+			rowNum:          425985, // 6.5 * (1 << 16) + 1
+			expectedB:       17,
+			expectedGrowing: true,
+		},
+	}
+
+	for _, tc := range cases {
+		aggMap := make(aggPartialResultMapper)
+		tempSlice := make([]aggfuncs.PartialResult, 10)
+		for num := 0; num < tc.rowNum; num++ {
+			aggMap[strconv.Itoa(num)] = tempSlice
+		}
+
+		c.Assert(getB(aggMap), Equals, tc.expectedB)
+		c.Assert(getGrowing(aggMap), Equals, tc.expectedGrowing)
+	}
+}
+
+// A header for a Go map.
+type hmap struct {
+	// Note: the format of the hmap is also encoded in cmd/compile/internal/gc/reflect.go.
+	// Make sure this stays in sync with the compiler's definition.
+	count     int // # live cells == size of map.  Must be first (used by len() builtin)
+	flags     uint8
+	B         uint8  // log_2 of # of buckets (can hold up to loadFactor * 2^B items)
+	noverflow uint16 // approximate number of overflow buckets; see incrnoverflow for details
+	hash0     uint32 // hash seed
+
+	buckets    unsafe.Pointer // array of 2^B Buckets. may be nil if count==0.
+	oldbuckets unsafe.Pointer // previous bucket array of half the size, non-nil only when growing
+	nevacuate  uintptr        // progress counter for evacuation (buckets less than this have been evacuated)
+
+	extra *mapextra // optional fields
+}
+
+// mapextra holds fields that are not present on all maps.
+type mapextra struct {
+	// If both key and elem do not contain pointers and are inline, then we mark bucket
+	// type as containing no pointers. This avoids scanning such maps.
+	// However, bmap.overflow is a pointer. In order to keep overflow buckets
+	// alive, we store pointers to all overflow buckets in hmap.extra.overflow and hmap.extra.oldoverflow.
+	// overflow and oldoverflow are only used if key and elem do not contain pointers.
+	// overflow contains overflow buckets for hmap.buckets.
+	// oldoverflow contains overflow buckets for hmap.oldbuckets.
+	// The indirection allows to store a pointer to the slice in hiter.
+	overflow    *[]*bmap
+	oldoverflow *[]*bmap
+
+	// nextOverflow holds a pointer to a free overflow bucket.
+	nextOverflow *bmap
+}
+
+const (
+	bucketCntBits = 3
+	bucketCnt     = 1 << bucketCntBits
+)
+
+// A bucket for a Go map.
+type bmap struct {
+	// tophash generally contains the top byte of the hash value
+	// for each key in this bucket. If tophash[0] < minTopHash,
+	// tophash[0] is a bucket evacuation state instead.
+	tophash [bucketCnt]uint8
+	// Followed by bucketCnt keys and then bucketCnt elems.
+	// NOTE: packing all the keys together and then all the elems together makes the
+	// code a bit more complicated than alternating key/elem/key/elem/... but it allows
+	// us to eliminate padding which would be needed for, e.g., map[int64]int8.
+	// Followed by an overflow pointer.
+}
+
+func getB(m aggPartialResultMapper) int {
+	point := (**hmap)(unsafe.Pointer(&m))
+	value := *point
+	return int(value.B)
+}
+
+func getGrowing(m aggPartialResultMapper) bool {
+	point := (**hmap)(unsafe.Pointer(&m))
+	value := *point
+	return value.oldbuckets != nil
+}