From 8db518f34e27ac3f26bdf210ad3d84bfca03de0a Mon Sep 17 00:00:00 2001
From: Yuanjia Zhang <zhangyuanjia@pingcap.com>
Date: Fri, 30 Apr 2021 10:48:36 +0800
Subject: [PATCH] solve the compatibility problem between UnionScan and
 PartitionTabel

---
 executor/builder.go         |  13 -----
 executor/partition_table.go | 100 ------------------------------------
 2 files changed, 113 deletions(-)

diff --git a/executor/builder.go b/executor/builder.go
index 45e5447f252c1..d940c8bbf4f0e 100644
--- a/executor/builder.go
+++ b/executor/builder.go
@@ -953,19 +953,6 @@ func (b *executorBuilder) buildUnionScanExec(v *plannercore.PhysicalUnionScan) E
 // Note that this function may be called by inner workers of index lookup join concurrently.
 // Be careful to avoid data race.
 func (b *executorBuilder) buildUnionScanFromReader(reader Executor, v *plannercore.PhysicalUnionScan) Executor {
-	// Adjust UnionScan->PartitionTable->Reader
-	// to PartitionTable->UnionScan->Reader
-	// The build of UnionScan executor is delay to the nextPartition() function
-	// because the Reader executor is available there.
-	if x, ok := reader.(*PartitionTableExecutor); ok {
-		nextPartitionForReader := x.nextPartition
-		x.nextPartition = nextPartitionForUnionScan{
-			b:     b,
-			us:    v,
-			child: nextPartitionForReader,
-		}
-		return x
-	}
 	// If reader is union, it means a partition table and we should transfer as above.
 	if x, ok := reader.(*UnionExec); ok {
 		for i, child := range x.children {
diff --git a/executor/partition_table.go b/executor/partition_table.go
index 3cebdec6c14e6..e888332fee396 100644
--- a/executor/partition_table.go
+++ b/executor/partition_table.go
@@ -17,58 +17,10 @@ import (
 	"context"
 	"fmt"
 
-	"github.com/opentracing/opentracing-go"
 	"github.com/pingcap/errors"
-	plannercore "github.com/pingcap/tidb/planner/core"
-	"github.com/pingcap/tidb/table"
-	"github.com/pingcap/tidb/util/chunk"
 	"github.com/pingcap/tipb/go-tipb"
 )
 
-// PartitionTableExecutor is a Executor for partitioned table.
-// It works by wrap the underlying TableReader/IndexReader/IndexLookUpReader.
-type PartitionTableExecutor struct {
-	baseExecutor
-
-	nextPartition
-	partitions []table.PhysicalTable
-	cursor     int
-	curr       Executor
-}
-
-type nextPartition interface {
-	nextPartition(context.Context, table.PhysicalTable) (Executor, error)
-}
-
-type nextPartitionForUnionScan struct {
-	b     *executorBuilder
-	us    *plannercore.PhysicalUnionScan
-	child nextPartition
-}
-
-// nextPartition implements the nextPartition interface.
-// For union scan on partitioned table, the executor should be PartitionTable->UnionScan->TableReader rather than
-// UnionScan->PartitionTable->TableReader
-func (n nextPartitionForUnionScan) nextPartition(ctx context.Context, tbl table.PhysicalTable) (Executor, error) {
-	childExec, err := n.child.nextPartition(ctx, tbl)
-	if err != nil {
-		return nil, err
-	}
-
-	n.b.err = nil
-	ret := n.b.buildUnionScanFromReader(childExec, n.us)
-	return ret, n.b.err
-}
-
-func nextPartitionWithTrace(ctx context.Context, n nextPartition, tbl table.PhysicalTable) (Executor, error) {
-	if span := opentracing.SpanFromContext(ctx); span != nil && span.Tracer() != nil {
-		span1 := span.Tracer().StartSpan(fmt.Sprintf("nextPartition %d", tbl.GetPhysicalID()), opentracing.ChildOf(span.Context()))
-		defer span1.Finish()
-		ctx = opentracing.ContextWithSpan(ctx, span1)
-	}
-	return n.nextPartition(ctx, tbl)
-}
-
 func updateExecutorTableID(ctx context.Context, exec *tipb.Executor, partitionID int64, recursive bool) error {
 	var child *tipb.Executor
 	switch exec.Tp {
@@ -105,55 +57,3 @@ func updateExecutorTableID(ctx context.Context, exec *tipb.Executor, partitionID
 	}
 	return nil
 }
-
-// Open implements the Executor interface.
-func (e *PartitionTableExecutor) Open(ctx context.Context) error {
-	e.cursor = 0
-	e.curr = nil
-	return nil
-}
-
-// Next implements the Executor interface.
-func (e *PartitionTableExecutor) Next(ctx context.Context, chk *chunk.Chunk) error {
-	chk.Reset()
-	var err error
-	for e.cursor < len(e.partitions) {
-		if e.curr == nil {
-			n := e.nextPartition
-			e.curr, err = nextPartitionWithTrace(ctx, n, e.partitions[e.cursor])
-			if err != nil {
-				return err
-			}
-			if err := e.curr.Open(ctx); err != nil {
-				return err
-			}
-		}
-
-		err = Next(ctx, e.curr, chk)
-		if err != nil {
-			return err
-		}
-
-		if chk.NumRows() > 0 {
-			break
-		}
-
-		err = e.curr.Close()
-		if err != nil {
-			return err
-		}
-		e.curr = nil
-		e.cursor++
-	}
-	return nil
-}
-
-// Close implements the Executor interface.
-func (e *PartitionTableExecutor) Close() error {
-	var err error
-	if e.curr != nil {
-		err = e.curr.Close()
-		e.curr = nil
-	}
-	return err
-}