executor: implement memDelta for count funcs to track memUsage (#19770)

* executor: implement memDelta for count funcs to track memUsage

* fix stdlib unsafe need be group together and before non-stdlib group in ../../executor/aggfuncs/func_count.go

* fix UpdatePartialResult memDelta return if err != nil

* fix
1 DefPartialResult4CountSize is the memory usage of AllocPartialResult, UpdatePartialResult will not use more memory, return 0, err.
2 in testcase TestMemCount count funcs are not distinct, use defaultUpdateMemDeltaGens and set isDistinct false

* fix UpdatePartialResult not use more memory

* fix  MergePartialResult memDelta

Co-authored-by: ti-srebot <66930949+ti-srebot@users.noreply.github.com>

executor/aggfuncs/func_count.go

@@ -14,18 +14,25 @@
 package aggfuncs
 
 import (
+	"unsafe"
+
 	"github.com/pingcap/tidb/sessionctx"
 	"github.com/pingcap/tidb/util/chunk"
 )
 
+const (
+	// DefPartialResult4CountSize is the size of partialResult4Count
+	DefPartialResult4CountSize = int64(unsafe.Sizeof(partialResult4Count(0)))
+)
+
 type baseCount struct {
 	baseAggFunc
 }
 
 type partialResult4Count = int64
 
 func (e *baseCount) AllocPartialResult() (pr PartialResult, memDelta int64) {
-	return PartialResult(new(partialResult4Count)), 0
+	return PartialResult(new(partialResult4Count)), DefPartialResult4CountSize
 }
 
 func (e *baseCount) ResetPartialResult(pr PartialResult) {

executor/aggfuncs/func_count_test.go

@@ -103,6 +103,20 @@ func (s *testSuite) TestCount(c *C) {
 
 func (s *testSuite) TestMemCount(c *C) {
 	tests := []aggMemTest{
+		buildAggMemTester(ast.AggFuncCount, mysql.TypeLonglong, 5,
+			aggfuncs.DefPartialResult4CountSize, defaultUpdateMemDeltaGens, false),
+		buildAggMemTester(ast.AggFuncCount, mysql.TypeFloat, 5,
+			aggfuncs.DefPartialResult4CountSize, defaultUpdateMemDeltaGens, false),
+		buildAggMemTester(ast.AggFuncCount, mysql.TypeDouble, 5,
+			aggfuncs.DefPartialResult4CountSize, defaultUpdateMemDeltaGens, false),
+		buildAggMemTester(ast.AggFuncCount, mysql.TypeNewDecimal, 5,
+			aggfuncs.DefPartialResult4CountSize, defaultUpdateMemDeltaGens, false),
+		buildAggMemTester(ast.AggFuncCount, mysql.TypeString, 5,
+			aggfuncs.DefPartialResult4CountSize, defaultUpdateMemDeltaGens, false),
+		buildAggMemTester(ast.AggFuncCount, mysql.TypeDate, 5,
+			aggfuncs.DefPartialResult4CountSize, defaultUpdateMemDeltaGens, false),
+		buildAggMemTester(ast.AggFuncCount, mysql.TypeDuration, 5,
+			aggfuncs.DefPartialResult4CountSize, defaultUpdateMemDeltaGens, false),
 		buildAggMemTester(ast.AggFuncCount, mysql.TypeLonglong, 5,
 			aggfuncs.DefPartialResult4CountDistinctIntSize, distinctUpdateMemDeltaGens, true),
 		buildAggMemTester(ast.AggFuncCount, mysql.TypeFloat, 5,