114 lines
3.4 KiB
Go
114 lines
3.4 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 plans
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import (
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"fmt"
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"github.com/pingcap/tidb/context"
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"github.com/pingcap/tidb/expression"
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"github.com/pingcap/tidb/expression/expressions"
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"github.com/pingcap/tidb/field"
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"github.com/pingcap/tidb/plan"
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"github.com/pingcap/tidb/util/format"
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)
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var (
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_ plan.Plan = (*SelectFieldsDefaultPlan)(nil)
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_ plan.Plan = (*SelectEmptyFieldListPlan)(nil)
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)
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// SelectFieldsDefaultPlan extracts specific fields from Src Plan.
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type SelectFieldsDefaultPlan struct {
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*SelectList
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Src plan.Plan
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}
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// Explain implements the plan.Plan Explain interface.
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func (r *SelectFieldsDefaultPlan) Explain(w format.Formatter) {
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// TODO: check for non existing fields
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r.Src.Explain(w)
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w.Format("┌Evaluate")
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for _, v := range r.Fields {
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w.Format(" %s as %s,", v.Expr, fmt.Sprintf("%q", v.Name))
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}
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w.Format("\n└Output field names %v\n", field.RFQNames(r.ResultFields))
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}
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// Filter implements the plan.Plan Filter interface.
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func (r *SelectFieldsDefaultPlan) Filter(ctx context.Context, expr expression.Expression) (plan.Plan, bool, error) {
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return r, false, nil
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}
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// Do implements the plan.Plan Do interface, extracts specific values by
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// r.Fields from row data.
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func (r *SelectFieldsDefaultPlan) Do(ctx context.Context, f plan.RowIterFunc) error {
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fields := r.Src.GetFields()
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m := map[interface{}]interface{}{}
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return r.Src.Do(ctx, func(rid interface{}, in []interface{}) (bool, error) {
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m[expressions.ExprEvalIdentFunc] = func(name string) (interface{}, error) {
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return getIdentValue(name, fields, in, field.DefaultFieldFlag)
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}
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out := make([]interface{}, len(r.Fields))
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for i, fld := range r.Fields {
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var err error
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if out[i], err = fld.Expr.Eval(ctx, m); err != nil {
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return false, err
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}
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}
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return f(rid, out)
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})
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}
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// SelectEmptyFieldListPlan is the plan for "select expr, expr, ..."" with no FROM.
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type SelectEmptyFieldListPlan struct {
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Fields []*field.Field
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}
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// Do implements the plan.Plan Do interface, returns empty row.
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func (s *SelectEmptyFieldListPlan) Do(ctx context.Context, f plan.RowIterFunc) error {
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// here we must output an empty row and don't evaluate fields
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// because we will evaluate fields later in SelectFieldsDefaultPlan or GroupByDefaultPlan
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values := make([]interface{}, len(s.Fields))
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if _, err := f(0, values); err != nil {
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return err
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}
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return nil
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}
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// Explain implements the plan.Plan Explain interface.
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func (s *SelectEmptyFieldListPlan) Explain(w format.Formatter) {
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// TODO: finish this
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}
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// GetFields implements the plan.Plan GetFields interface.
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func (s *SelectEmptyFieldListPlan) GetFields() []*field.ResultField {
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ans := make([]*field.ResultField, 0, len(s.Fields))
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if len(s.Fields) > 0 {
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for _, f := range s.Fields {
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nm := f.Name
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ans = append(ans, &field.ResultField{Name: nm})
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}
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}
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return ans
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}
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// Filter implements the plan.Plan Filter interface.
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func (s *SelectEmptyFieldListPlan) Filter(ctx context.Context, expr expression.Expression) (plan.Plan, bool, error) {
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return s, false, nil
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}
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