forked from cockroachdb/cockroach
/
parse.go
143 lines (125 loc) · 3.85 KB
/
parse.go
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// Copyright 2015 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: Peter Mattis (peter@cockroachlabs.com)
// This code was derived from https://github.com/youtube/vitess.
//
// Copyright 2012, Google Inc. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file
package parser
import (
"bytes"
"errors"
"github.com/cockroachdb/cockroach/util"
)
//go:generate make
// StatementList is a list of statements.
type StatementList []Statement
func (l StatementList) String() string {
var buf bytes.Buffer
for i, s := range l {
if i > 0 {
buf.WriteString("; ")
}
buf.WriteString(s.String())
}
return buf.String()
}
// Syntax is an enum of the various syntax types.
type Syntax int
//go:generate stringer -type=Syntax
const (
// Implicit default, must stay in the zero-value position.
Traditional Syntax = iota
Modern
)
// Parser wraps a scanner, parser and other utilities present in the parser
// package.
type Parser struct {
scanner scanner
parserImpl sqlParserImpl
normalizeVisitor normalizeVisitor
}
// Parse parses the sql and returns a list of statements.
func (p *Parser) Parse(sql string, syntax Syntax) (stmts StatementList, err error) {
defer func() {
switch r := recover(); r {
case nil:
case errUnimplemented:
err = errUnimplemented
default:
panic(r)
}
}()
p.scanner.init(sql, syntax)
if p.parserImpl.Parse(&p.scanner) != 0 {
return nil, errors.New(p.scanner.lastError)
}
return p.scanner.stmts, nil
}
// NormalizeExpr is wrapper around ctx.NormalizeExpr which avoids allocation of
// a normalizeVisitor.
func (p *Parser) NormalizeExpr(ctx EvalContext, expr Expr) (Expr, error) {
p.normalizeVisitor = normalizeVisitor{ctx: ctx}
expr, _ = WalkExpr(&p.normalizeVisitor, expr)
return expr, p.normalizeVisitor.err
}
// parse parses the sql and returns a list of statements.
func parse(sql string, syntax Syntax) (StatementList, error) {
var p Parser
return p.Parse(sql, syntax)
}
// parseTraditional is short-hand for parse(sql, Traditional)
func parseTraditional(sql string) (StatementList, error) {
return parse(sql, Traditional)
}
// ParseOne parses a sql statement.
func ParseOne(sql string, syntax Syntax) (Statement, error) {
stmts, err := parse(sql, syntax)
if err != nil {
return nil, err
}
if len(stmts) != 1 {
return nil, util.Errorf("expected 1 statement, but found %d", len(stmts))
}
return stmts[0], nil
}
// ParseOneTraditional is short-hand for ParseOne(sql, Traditional)
func ParseOneTraditional(sql string) (Statement, error) {
return ParseOne(sql, Traditional)
}
// parseExpr parses a sql expression.
func parseExpr(expr string, syntax Syntax) (Expr, error) {
stmt, err := ParseOne(`SELECT `+expr, syntax)
if err != nil {
return nil, err
}
sel, ok := stmt.(*Select)
if !ok {
return nil, util.Errorf("expected a SELECT statement, but found %T", stmt)
}
selClause, ok := sel.Select.(*SelectClause)
if !ok {
return nil, util.Errorf("expected a SELECT statement, but found %T", sel.Select)
}
if n := len(selClause.Exprs); n != 1 {
return nil, util.Errorf("expected 1 expression, but found %d", n)
}
return selClause.Exprs[0].Expr, nil
}
// ParseExprTraditional is a short-hand for parseExpr(sql, Traditional)
func ParseExprTraditional(sql string) (Expr, error) {
return parseExpr(sql, Traditional)
}