planner, expression: support multi-distinct agg under MPP mode

executor/partition_table.go

@@ -56,6 +56,8 @@ func updateExecutorTableID(ctx context.Context, exec *tipb.Executor, recursive b
 		child = exec.Window.Child
 	case tipb.ExecType_TypeSort:
 		child = exec.Sort.Child
+	case tipb.ExecType_TypeExpand:
+		child = exec.Expand.Child
 	default:
 		return errors.Trace(fmt.Errorf("unknown new tipb protocol %d", exec.Tp))
 	}

expression/BUILD.bazel

@@ -54,6 +54,7 @@ go_library(
         "expression.go",
         "extension.go",
         "function_traits.go",
+        "grouping_sets.go",
         "helper.go",
         "partition_pruner.go",
         "scalar_function.go",
@@ -78,6 +79,7 @@ go_library(
         "//parser/opcode",
         "//parser/terror",
         "//parser/types",
+        "//planner/funcdep",
         "//privilege",
         "//sessionctx",
         "//sessionctx/stmtctx",
@@ -171,6 +173,7 @@ go_test(
         "expr_to_pb_test.go",
         "expression_test.go",
         "function_traits_test.go",
+        "grouping_sets_test.go",
         "helper_test.go",
         "main_test.go",
         "multi_valued_index_test.go",
@@ -227,6 +230,7 @@ go_test(
         "@com_github_stretchr_testify//require",
         "@com_github_tikv_client_go_v2//oracle",
         "@com_github_tikv_client_go_v2//tikv",
+        "@io_opencensus_go//stats/view",
         "@org_uber_go_goleak//:goleak",
     ],
 )

expression/aggregation/descriptor.go

@@ -42,6 +42,8 @@ type AggFuncDesc struct {
 	HasDistinct bool
 	// OrderByItems represents the order by clause used in GROUP_CONCAT
 	OrderByItems []*util.ByItems
+	// GroupingID is used for distinguishing with not-set 0, starting from 1.
+	GroupingID int
 }
 
 // NewAggFuncDesc creates an aggregation function signature descriptor.

expression/constant.go

@@ -52,6 +52,18 @@ func NewZero() *Constant {
 	}
 }
 
+// NewUInt64Const stands for constant of a given number.
+func NewUInt64Const(num int) *Constant {
+	retT := types.NewFieldType(mysql.TypeLonglong)
+	retT.AddFlag(mysql.UnsignedFlag) // shrink range to avoid integral promotion
+	retT.SetFlen(mysql.MaxIntWidth)
+	retT.SetDecimal(0)
+	return &Constant{
+		Value:   types.NewDatum(num),
+		RetType: retT,
+	}
+}
+
 // NewNull stands for null constant.
 func NewNull() *Constant {
 	retT := types.NewFieldType(mysql.TypeTiny)