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returning.go
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returning.go
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// Copyright 2016 The Cockroach Authors.
//
// Licensed 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.
//
// Author: Matt Jibson (mjibson@cockroachlabs.com)
package parser
import "bytes"
// ReturningClause represents the returning clause on a statement.
type ReturningClause interface {
NodeFormatter
// statementType returns the StatementType of statements that include
// the implementors variant of a RETURNING clause.
statementType() StatementType
returningClause()
}
var _ ReturningClause = &ReturningExprs{}
var _ ReturningClause = &ReturningNothing{}
var _ ReturningClause = &NoReturningClause{}
// ReturningExprs represents RETURNING expressions.
type ReturningExprs SelectExprs
// Format implements the NodeFormatter interface.
func (r *ReturningExprs) Format(buf *bytes.Buffer, f FmtFlags) {
buf.WriteString(" RETURNING ")
FormatNode(buf, f, SelectExprs(*r))
}
// Shared instance to avoid unnecessary allocations.
var returningNothingClause = &ReturningNothing{}
// ReturningNothing represents RETURNING NOTHING.
type ReturningNothing struct{}
// Format implements the NodeFormatter interface.
func (*ReturningNothing) Format(buf *bytes.Buffer, f FmtFlags) {
buf.WriteString(" RETURNING NOTHING")
}
// AbsentReturningClause is a ReturningClause variant representing the absence of
// a RETURNING clause.
var AbsentReturningClause = &NoReturningClause{}
// NoReturningClause represents the absence of a RETURNING clause.
type NoReturningClause struct{}
// Format implements the NodeFormatter interface.
func (*NoReturningClause) Format(buf *bytes.Buffer, f FmtFlags) {}
// used by parent statements to determine their own StatementType.
func (*ReturningExprs) statementType() StatementType { return Rows }
func (*ReturningNothing) statementType() StatementType { return RowsAffected }
func (*NoReturningClause) statementType() StatementType { return RowsAffected }
func (*ReturningExprs) returningClause() {}
func (*ReturningNothing) returningClause() {}
func (*NoReturningClause) returningClause() {}
// HasReturningClause determines if a ReturningClause is present, given a
// variant of the ReturningClause interface.
func HasReturningClause(clause ReturningClause) bool {
_, ok := clause.(*NoReturningClause)
return !ok
}