70 lines
1.9 KiB
Go
70 lines
1.9 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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)
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// ExistsSubQuery is the expression for "exists (select ...)".
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// https://dev.mysql.com/doc/refman/5.7/en/exists-and-not-exists-subqueries.html
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type ExistsSubQuery struct {
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// Sel is the sub query.
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Sel SubQuery
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}
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// Clone implements the Expression Clone interface.
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func (es *ExistsSubQuery) Clone() Expression {
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sel := es.Sel.Clone()
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return &ExistsSubQuery{Sel: sel.(SubQuery)}
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}
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// IsStatic implements the Expression IsStatic interface.
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func (es *ExistsSubQuery) IsStatic() bool {
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return es.Sel.IsStatic()
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}
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// String implements the Expression String interface.
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func (es *ExistsSubQuery) String() string {
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return fmt.Sprintf("EXISTS %s", es.Sel)
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}
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// Eval implements the Expression Eval interface.
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func (es *ExistsSubQuery) Eval(ctx context.Context, args map[interface{}]interface{}) (interface{}, error) {
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if !es.Sel.UseOuterQuery() && es.Sel.Value() != nil {
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return es.Sel.Value().(bool), nil
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}
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rows, err := es.Sel.EvalRows(ctx, args, 1)
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if err != nil {
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return nil, errors.Trace(err)
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}
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es.Sel.SetValue(len(rows) > 0)
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return es.Sel.Value(), nil
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}
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// Accept implements Expression Accept interface.
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func (es *ExistsSubQuery) Accept(v Visitor) (Expression, error) {
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return v.VisitExistsSubQuery(es)
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}
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// NewExistsSubQuery creates a ExistsSubQuery object.
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func NewExistsSubQuery(sel SubQuery) *ExistsSubQuery {
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return &ExistsSubQuery{Sel: sel}
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}
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