github.com/cockroachdb/cockroach@v20.2.0-alpha.1+incompatible/pkg/sql/buffer.go (about)

     1  // Copyright 2019 The Cockroach Authors.
     2  //
     3  // Use of this software is governed by the Business Source License
     4  // included in the file licenses/BSL.txt.
     5  //
     6  // As of the Change Date specified in that file, in accordance with
     7  // the Business Source License, use of this software will be governed
     8  // by the Apache License, Version 2.0, included in the file
     9  // licenses/APL.txt.
    10  
    11  package sql
    12  
    13  import (
    14  	"context"
    15  
    16  	"github.com/cockroachdb/cockroach/pkg/sql/rowcontainer"
    17  	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
    18  	"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
    19  )
    20  
    21  // bufferNode consumes its input one row at a time, stores it in the buffer,
    22  // and passes the row through. The buffered rows can be iterated over multiple
    23  // times.
    24  type bufferNode struct {
    25  	plan planNode
    26  
    27  	// TODO(yuzefovich): the buffer should probably be backed by disk. If so, the
    28  	// comments about TempStorage suggest that it should be used by DistSQL
    29  	// processors, but this node is local.
    30  	bufferedRows       *rowcontainer.RowContainer
    31  	passThruNextRowIdx int
    32  
    33  	// label is a string used to describe the node in an EXPLAIN plan.
    34  	label string
    35  }
    36  
    37  // BufferNodeMarker is part of the exec.BufferNode interface.
    38  func (n *bufferNode) BufferNodeMarker() {}
    39  
    40  func (n *bufferNode) startExec(params runParams) error {
    41  	n.bufferedRows = rowcontainer.NewRowContainer(
    42  		params.EvalContext().Mon.MakeBoundAccount(),
    43  		sqlbase.ColTypeInfoFromResCols(getPlanColumns(n.plan, false /* mut */)),
    44  		0, /* rowCapacity */
    45  	)
    46  	return nil
    47  }
    48  
    49  func (n *bufferNode) Next(params runParams) (bool, error) {
    50  	if err := params.p.cancelChecker.Check(); err != nil {
    51  		return false, err
    52  	}
    53  	ok, err := n.plan.Next(params)
    54  	if err != nil {
    55  		return false, err
    56  	}
    57  	if !ok {
    58  		return false, nil
    59  	}
    60  	if _, err = n.bufferedRows.AddRow(params.ctx, n.plan.Values()); err != nil {
    61  		return false, err
    62  	}
    63  	n.passThruNextRowIdx++
    64  	return true, nil
    65  }
    66  
    67  func (n *bufferNode) Values() tree.Datums {
    68  	return n.bufferedRows.At(n.passThruNextRowIdx - 1)
    69  }
    70  
    71  func (n *bufferNode) Close(ctx context.Context) {
    72  	n.plan.Close(ctx)
    73  	n.bufferedRows.Close(ctx)
    74  }
    75  
    76  // scanBufferNode behaves like an iterator into the bufferNode it is
    77  // referencing. The bufferNode can be iterated over multiple times
    78  // simultaneously, however, a new scanBufferNode is needed.
    79  type scanBufferNode struct {
    80  	buffer *bufferNode
    81  
    82  	nextRowIdx int
    83  
    84  	// label is a string used to describe the node in an EXPLAIN plan.
    85  	label string
    86  }
    87  
    88  func (n *scanBufferNode) startExec(runParams) error {
    89  	return nil
    90  }
    91  
    92  func (n *scanBufferNode) Next(runParams) (bool, error) {
    93  	n.nextRowIdx++
    94  	return n.nextRowIdx <= n.buffer.bufferedRows.Len(), nil
    95  }
    96  
    97  func (n *scanBufferNode) Values() tree.Datums {
    98  	return n.buffer.bufferedRows.At(n.nextRowIdx - 1)
    99  }
   100  
   101  func (n *scanBufferNode) Close(context.Context) {
   102  }