feature: support nextval and currval

pkg/runtime/optimize/dml/select.go

@@ -56,9 +56,13 @@ func optimizeSelect(ctx context.Context, o *optimize.Optimizer) (proto.Plan, err
 	stmt := o.Stmt.(*ast.SelectStatement)
 	enableLocalMathComputation := ctx.Value(proto.ContextKeyEnableLocalComputation{}).(bool)
 	if enableLocalMathComputation && len(stmt.From) == 0 {
-		isLocalFlag := true
-		var columnList []string
-		var valueList []proto.Value
+		var (
+			isLocalFlag = true
+			isSequence  = false
+			columnList  []string
+			valueList   []proto.Value
+			vts         []*rule.VTable
+		)
 		for i := range stmt.Select {
 			switch selectItem := stmt.Select[i].(type) {
 			case *ast.SelectElementExpr:
@@ -94,9 +98,26 @@ func optimizeSelect(ctx context.Context, o *optimize.Optimizer) (proto.Plan, err
 				}
 				valueList = append(valueList, calculateRes)
 				columnList = append(columnList, stmt.Select[i].DisplayName())
-
+			case *ast.SelectElementColumn:
+				if len(selectItem.Name) == 2 && (strings.ToLower(selectItem.Name[1]) == "currval" || strings.ToLower(selectItem.Name[1]) == "nextval") {
+					isSequence = true
+					vt, ok := o.Rule.VTable(selectItem.Name[0])
+					if !ok {
+						return nil, proto.ErrorNotFoundSequence
+					}
+					vts = append(vts, vt)
+				}
 			}
 		}
+		if isSequence {
+			ret := &dml.LocalSequencePlan{
+				Stmt:       stmt,
+				VTs:        vts,
+				ColumnList: columnList,
+			}
+			ret.BindArgs(o.Args)
+			return ret, nil
+		}
 		if isLocalFlag {
 
 			ret := &dml.LocalSelectPlan{

pkg/runtime/plan/dml/local_select.go

@@ -49,7 +49,9 @@ func (s *LocalSelectPlan) Type() proto.PlanType {
 func (s *LocalSelectPlan) ExecIn(ctx context.Context, _ proto.VConn) (proto.Result, error) {
 	_, span := plan.Tracer.Start(ctx, "LocalSelectPlan.ExecIn")
 	defer span.End()
-	var theadLocalSelect thead.Thead
+	var (
+		theadLocalSelect thead.Thead
+	)
 
 	for i, item := range s.ColumnList {
 		sRes := s.Result[i].String()

pkg/runtime/plan/dml/local_sequence.go

@@ -0,0 +1,96 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package dml
+
+import (
+	"context"
+	rcontext "github.com/arana-db/arana/pkg/runtime/context"
+	"github.com/pkg/errors"
+	"strings"
+)
+
+import (
+	consts "github.com/arana-db/arana/pkg/constants/mysql"
+	"github.com/arana-db/arana/pkg/dataset"
+	"github.com/arana-db/arana/pkg/mysql/rows"
+	"github.com/arana-db/arana/pkg/mysql/thead"
+	"github.com/arana-db/arana/pkg/proto"
+	"github.com/arana-db/arana/pkg/proto/rule"
+	"github.com/arana-db/arana/pkg/resultx"
+	"github.com/arana-db/arana/pkg/runtime/ast"
+	"github.com/arana-db/arana/pkg/runtime/plan"
+)
+
+var _ proto.Plan = (*LocalSequencePlan)(nil)
+
+type LocalSequencePlan struct {
+	plan.BasePlan
+	Stmt       *ast.SelectStatement
+	VTs        []*rule.VTable
+	ColumnList []string
+}
+
+func (s *LocalSequencePlan) Type() proto.PlanType {
+	return proto.PlanTypeQuery
+}
+
+func (s *LocalSequencePlan) ExecIn(ctx context.Context, _ proto.VConn) (proto.Result, error) {
+	_, span := plan.Tracer.Start(ctx, "LocalSequencePlan.ExecIn")
+
+	defer span.End()
+	var (
+		theadLocalSelect thead.Thead
+		columns          []proto.Field
+		values           []proto.Value
+	)
+
+	for idx := 0; s.Stmt.From == nil && idx < len(s.Stmt.Select); idx++ {
+		if seqColumn, ok := s.Stmt.Select[idx].(*ast.SelectElementColumn); ok && len(seqColumn.Name) == 2 {
+			seqName, seqFunc := seqColumn.Name[0], seqColumn.Name[1]
+			colName := seqColumn.Alias()
+			if colName == "" {
+				colName = strings.Join(seqColumn.Name, ".")
+			}
+			theadLocalSelect = append(theadLocalSelect, thead.Col{Name: colName, FieldType: consts.FieldTypeLong})
+			seq, err := proto.LoadSequenceManager().GetSequence(ctx, rcontext.Tenant(ctx), rcontext.Schema(ctx), seqName)
+			if err != nil {
+				return nil, errors.WithStack(err)
+			}
+
+			switch strings.ToLower(seqFunc) {
+			case "currval":
+				values = append(values, proto.NewValueInt64(seq.(proto.EnhancedSequence).CurrentVal()))
+			case "nextval":
+				nextSeqVal, err := seq.Acquire(ctx)
+				if err != nil {
+					return nil, err
+				}
+				values = append(values, proto.NewValueInt64(nextSeqVal))
+			}
+		}
+	}
+
+	columns = theadLocalSelect.ToFields()
+	ds := &dataset.VirtualDataset{
+		Columns: columns,
+	}
+
+	ds.Rows = append(ds.Rows, rows.NewTextVirtualRow(columns, values))
+	return resultx.New(resultx.WithDataset(ds)), nil
+
+}

test/integration_test.go

@@ -21,8 +21,11 @@
 package test
 
 import (
+	"context"
 	"database/sql"
 	"fmt"
+	"github.com/arana-db/arana/pkg/proto"
+	"github.com/arana-db/arana/pkg/runtime"
 	"sort"
 	"strconv"
 	"strings"
@@ -1350,3 +1353,60 @@ func (s *IntegrationSuite) TestMysqlOptimizerHints() {
 		})
 	}
 }
+
+func (s *IntegrationSuite) TestSequence() {
+	var (
+		db = s.DB()
+		t  = s.T()
+	)
+
+	rt, err := runtime.Load("arana", "employees")
+	if err != nil {
+		panic(err)
+	}
+	ctx := context.WithValue(context.Background(), proto.RuntimeCtxKey{}, rt)
+	ctx = context.WithValue(ctx, proto.ContextKeyTenant{}, "arana")
+	ctx = context.WithValue(ctx, proto.ContextKeySchema{}, "employees")
+	_, err = proto.LoadSequenceManager().CreateSequence(ctx, "arana", "employees", proto.SequenceConfig{Name: "student", Type: "group"})
+	if err != nil {
+		panic(err)
+	}
+
+	type testCase struct {
+		sql       string
+		exceptVal int64
+	}
+
+	for _, it := range [...]testCase{
+		{
+			"select student.nextVal",
+			1,
+		},
+		{
+			"select student.currVal",
+			1,
+		},
+		{
+			"select student.nextVal",
+			2,
+		},
+		{
+			"select notexist.currVal",
+			-1,
+		},
+	} {
+		t.Run(it.sql, func(t *testing.T) {
+			rows, err := db.Query(it.sql)
+			if it.exceptVal == -1 {
+				assert.True(t, err != nil, err)
+				return
+			}
+			defer rows.Close()
+			assert.NoError(t, err, "should query successfully")
+			var val int64
+			records, _ := utils.PrintTable(rows)
+			val, err = strconv.ParseInt(records[0][0], 10, 64)
+			assert.Equal(t, it.exceptVal, val)
+		})
+	}
+}