github.com/vescale/zgraph@v0.0.0-20230410094002-959c02d50f95/executor/simple.go (about) 1 // Copyright 2022 zGraph Authors. All rights reserved. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 package executor 16 17 import ( 18 "context" 19 20 "github.com/pingcap/errors" 21 "github.com/vescale/zgraph/datum" 22 "github.com/vescale/zgraph/meta" 23 "github.com/vescale/zgraph/parser/ast" 24 ) 25 26 // SimpleExec is used to execute some simple tasks. 27 type SimpleExec struct { 28 baseExecutor 29 30 done bool 31 statement ast.StmtNode 32 } 33 34 func (e *SimpleExec) Next(_ context.Context) (datum.Row, error) { 35 if e.done { 36 return nil, nil 37 } 38 e.done = true 39 40 switch stmt := e.statement.(type) { 41 case *ast.UseStmt: 42 return nil, e.execUse(stmt) 43 default: 44 return nil, errors.Errorf("unknown statement: %T", e.statement) 45 } 46 } 47 48 func (e *SimpleExec) execUse(stmt *ast.UseStmt) error { 49 graph := e.sc.Catalog().Graph(stmt.GraphName.L) 50 if graph == nil { 51 return meta.ErrGraphNotExists 52 } 53 54 e.sc.SetCurrentGraphName(stmt.GraphName.L) 55 56 return nil 57 }