forked from pingcap/tidb
/
fields.go
87 lines (75 loc) · 2.29 KB
/
fields.go
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// Copyright 2015 PingCAP, 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,
// See the License for the specific language governing permissions and
// limitations under the License.
package rsets
import (
"strings"
"github.com/pingcap/tidb/context"
"github.com/pingcap/tidb/expression/expressions"
"github.com/pingcap/tidb/field"
"github.com/pingcap/tidb/plan"
"github.com/pingcap/tidb/plan/plans"
)
var (
_ plan.Planner = (*SelectFieldsRset)(nil)
_ plan.Planner = (*FieldRset)(nil)
)
// SelectFieldsRset is record set to select fields.
type SelectFieldsRset struct {
Src plan.Plan
SelectList *plans.SelectList
}
// Plan gets SrcPlan/SelectFieldsDefaultPlan.
// If all fields are equal to src plan fields, then gets SrcPlan.
// Default gets SelectFieldsDefaultPlan.
func (r *SelectFieldsRset) Plan(ctx context.Context) (plan.Plan, error) {
fields := r.SelectList.Fields
srcFields := r.Src.GetFields()
if len(fields) == len(srcFields) {
match := true
for i, v := range fields {
// TODO: is it this check enough? e.g, the ident field is t.c.
if x, ok := v.Expr.(*expressions.Ident); ok && strings.EqualFold(x.L, srcFields[i].Name) && strings.EqualFold(v.Name, srcFields[i].Name) {
continue
}
match = false
break
}
if match {
return r.Src, nil
}
}
src := r.Src
if x, ok := src.(*plans.TableDefaultPlan); ok {
// check whether src plan will be set TableNilPlan, like `select 1, 2 from t`.
isConst := true
for _, v := range fields {
if expressions.FastEval(v.Expr) == nil {
isConst = false
break
}
}
if isConst {
src = &plans.TableNilPlan{T: x.T}
}
}
p := &plans.SelectFieldsDefaultPlan{Src: src, SelectList: r.SelectList}
return p, nil
}
// FieldRset is Recordset for select expression, like `select 1, 1+1`.
type FieldRset struct {
Fields []*field.Field
}
// Plan gets SelectExprPlan.
func (r *FieldRset) Plan(ctx context.Context) (plan.Plan, error) {
return &plans.SelectEmptyFieldListPlan{Fields: r.Fields}, nil
}