100 lines
2.2 KiB
Go
100 lines
2.2 KiB
Go
// Copyright 2015 PingCAP, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package expression
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import (
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"fmt"
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"github.com/juju/errors"
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"github.com/pingcap/tidb/context"
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"github.com/pingcap/tidb/util/types"
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)
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var (
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_ Expression = (*IsTruth)(nil)
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)
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// IsTruth is the expression for true/false check.
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type IsTruth struct {
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// Expr is the expression to be checked.
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Expr Expression
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// Not is true, the expression is "is not true/false".
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Not bool
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// True indicates checking true or false.
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True int64
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}
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// Clone implements the Expression Clone interface.
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func (is *IsTruth) Clone() Expression {
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expr := is.Expr.Clone()
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return &IsTruth{Expr: expr, Not: is.Not, True: is.True}
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}
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// IsStatic implements the Expression IsStatic interface.
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func (is *IsTruth) IsStatic() bool {
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return is.Expr.IsStatic()
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}
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// String implements the Expression String interface.
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func (is *IsTruth) String() string {
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not := ""
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if is.Not {
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not = "NOT "
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}
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truth := "TRUE"
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if is.True == 0 {
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truth = "FALSE"
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}
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return fmt.Sprintf("%s IS %s%s", is.Expr, not, truth)
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}
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// Eval implements the Expression Eval interface.
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func (is *IsTruth) Eval(ctx context.Context, args map[interface{}]interface{}) (v interface{}, err error) {
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if err := CheckOneColumn(ctx, is.Expr); err != nil {
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return nil, errors.Trace(err)
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}
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val, err := is.Expr.Eval(ctx, args)
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if err != nil {
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return
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}
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if val == nil {
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// null is true/false -> false
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// null is not true/false -> true
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return is.Not, nil
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}
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b, err := types.ToBool(val)
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if err != nil {
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return
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}
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if !is.Not {
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// true/false is true/false
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return b == is.True, nil
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}
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// true/false is not true/false
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return b != is.True, nil
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}
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// Accept implements Expression Accept interface.
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func (is *IsTruth) Accept(v Visitor) (Expression, error) {
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return v.VisitIsTruth(is)
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}
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