79 lines
1.9 KiB
Go
79 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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"strings"
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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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var (
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_ Expression = (*Default)(nil)
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)
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// Default is the default expression using default value for a column.
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type Default struct {
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// Name is the column name
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Name string
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}
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// Clone implements the Expression Clone interface.
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func (d *Default) Clone() Expression {
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newV := *d
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return &newV
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}
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// IsStatic implements the Expression IsStatic interface, always returns false.
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func (d *Default) IsStatic() bool {
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return false
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}
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// String implements the Expression String interface.
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func (d *Default) String() string {
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if d.Name == "" {
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return "default"
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}
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return fmt.Sprintf("default (%s)", strings.ToLower(d.Name))
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}
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// Eval implements the Expression Eval interface.
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func (d *Default) Eval(ctx context.Context, args map[interface{}]interface{}) (interface{}, error) {
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name := strings.ToLower(d.Name)
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if name == "" {
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// if name is empty, the stmt may like "insert into t values (default)"
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// we will use the corresponding column name
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colName, ok := args[ExprEvalDefaultName]
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if !ok {
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return nil, errors.Errorf("default column not found - %s", name)
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}
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name = colName.(string)
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}
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vv, ok := args[name]
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if ok {
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return vv, nil
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}
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return nil, errors.Errorf("default column not found - %s", name)
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}
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// Accept implements Expression Accept interface.
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func (d *Default) Accept(v Visitor) (Expression, error) {
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return v.VisitDefault(d)
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}
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