precedence.go

/*
Copyright 2019 The Vitess 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.
*/

package sqlparser

// Precendence is used to know the precedence between operators,
// so we can introduce parens when needed in the String representation of the AST
type Precendence int

const (
	Syntactic Precendence = iota
	P1
	P2
	P3
	P4
	P5
	P6
	P7
	P8
	P9
	P10
	P11
	P12
	P13
	P14
	P15
	P16
	P17
)

// precedenceFor returns the precedence of an expression.
//
//   - NOTE: If you change anything here, update sql.y to keep them consistent.
//     Also make sure to add the new constructs to random_expr.go so we have test coverage for the new expressions *
func precedenceFor(in Expr) Precendence {
	switch node := in.(type) {
	case *OrExpr:
		return P16
	case *XorExpr:
		return P15
	case *AndExpr:
		return P14
	case *NotExpr:
		return P13
	case *BetweenExpr:
		return P12
	case *ComparisonExpr:
		switch node.Operator {
		case EqualOp, NotEqualOp, GreaterThanOp, GreaterEqualOp, LessThanOp, LessEqualOp, LikeOp, InOp, RegexpOp, NullSafeEqualOp:
			return P11
		}
	case *IsExpr:
		return P11
	case *BinaryExpr:
		switch node.Operator {
		case BitOrOp:
			return P10
		case BitAndOp:
			return P9
		case ShiftLeftOp, ShiftRightOp:
			return P8
		case PlusOp, MinusOp:
			return P7
		case DivOp, MultOp, ModOp, IntDivOp:
			return P6
		case BitXorOp:
			return P5
		}
	case *UnaryExpr:
		switch node.Operator {
		case UPlusOp, UMinusOp:
			return P4
		case BangOp:
			return P3
		}
	}

	return Syntactic
}