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common.go
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common.go
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// Copyright 2020-2021 Dolthub, Inc.
//
// 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 expression
import (
"github.com/Rock-liyi/p2pdb-store/sql"
)
// IsUnary returns whether the expression is unary or not.
func IsUnary(e sql.Expression) bool {
return len(e.Children()) == 1
}
// IsBinary returns whether the expression is binary or not.
func IsBinary(e sql.Expression) bool {
return len(e.Children()) == 2
}
// UnaryExpression is an expression that has only one children.
type UnaryExpression struct {
Child sql.Expression
}
// Children implements the Expression interface.
func (p *UnaryExpression) Children() []sql.Expression {
return []sql.Expression{p.Child}
}
// Resolved implements the Expression interface.
func (p *UnaryExpression) Resolved() bool {
return p.Child.Resolved()
}
// IsNullable returns whether the expression can be null.
func (p *UnaryExpression) IsNullable() bool {
return p.Child.IsNullable()
}
// BinaryExpression is an expression that has two children.
type BinaryExpression struct {
Left sql.Expression
Right sql.Expression
}
// Children implements the Expression interface.
func (p *BinaryExpression) Children() []sql.Expression {
return []sql.Expression{p.Left, p.Right}
}
// Resolved implements the Expression interface.
func (p *BinaryExpression) Resolved() bool {
return p.Left.Resolved() && p.Right.Resolved()
}
// IsNullable returns whether the expression can be null.
func (p *BinaryExpression) IsNullable() bool {
return p.Left.IsNullable() || p.Right.IsNullable()
}
type NaryExpression struct {
ChildExpressions []sql.Expression
}
// Children implements the Expression interface.
func (n *NaryExpression) Children() []sql.Expression {
return n.ChildExpressions
}
// Resolved implements the Expression interface.
func (n *NaryExpression) Resolved() bool {
for _, child := range n.Children() {
if !child.Resolved() {
return false
}
}
return true
}
// IsNullable returns whether the expression can be null.
func (n *NaryExpression) IsNullable() bool {
for _, child := range n.Children() {
if child.IsNullable() {
return true
}
}
return false
}
// ExpressionsResolve returns whether all the expressions in the slice given are resolved
func ExpressionsResolved(exprs ...sql.Expression) bool {
for _, e := range exprs {
if !e.Resolved() {
return false
}
}
return true
}
func Dispose(e sql.Expression) {
sql.Inspect(e, func(e sql.Expression) bool {
sql.Dispose(e)
return true
})
}