041dfd97c1
* executor: evaluate subquery before executing outer query. So outer query can push down subquery values. * evaluator: extract a function to evaluate subquery. * evaluator: add comments on exported function.
98 lines
2.0 KiB
Go
98 lines
2.0 KiB
Go
// Copyright 2016 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 executor
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import (
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"github.com/juju/errors"
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"github.com/pingcap/tidb/ast"
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"github.com/pingcap/tidb/context"
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"github.com/pingcap/tidb/infoschema"
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"github.com/pingcap/tidb/optimizer/plan"
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"github.com/pingcap/tidb/util/types"
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)
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var _ ast.SubqueryExec = &subquery{}
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// subquery is an exprNode with a plan.
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type subquery struct {
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types.Datum
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Type *types.FieldType
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flag uint64
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text string
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plan plan.Plan
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is infoschema.InfoSchema
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}
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func (sq *subquery) EvalRows(ctx context.Context, rowCount int) ([]types.Datum, error) {
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b := newExecutorBuilder(ctx, sq.is)
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plan.Refine(sq.plan)
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e := b.build(sq.plan)
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if b.err != nil {
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return nil, errors.Trace(b.err)
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}
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defer e.Close()
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if len(e.Fields()) == 0 {
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// No result fields means no Recordset.
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for {
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row, err := e.Next()
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if err != nil {
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return nil, errors.Trace(err)
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}
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if row == nil {
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return nil, nil
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}
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}
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}
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var (
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err error
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row *Row
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rows []types.Datum
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)
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for rowCount != 0 {
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row, err = e.Next()
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if err != nil {
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return rows, errors.Trace(err)
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}
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if row == nil {
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break
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}
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if len(row.Data) == 1 {
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rows = append(rows, row.Data[0])
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} else {
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var d types.Datum
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d.SetRow(row.Data)
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rows = append(rows, d)
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}
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if rowCount > 0 {
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rowCount--
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}
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}
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return rows, nil
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}
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func (sq *subquery) ColumnCount() (int, error) {
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return len(sq.plan.Fields()), nil
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}
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type subqueryBuilder struct {
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is infoschema.InfoSchema
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}
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func (sb *subqueryBuilder) Build(p plan.Plan) ast.SubqueryExec {
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return &subquery{
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is: sb.is,
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plan: p,
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}
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}
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