sql: add buffer and scanBuffer nodes

Adds bufferNode that consumes its input, stores all the rows in a
buffer, and then proceeds on passing the rows through. The buffer
can be iterated over multiple times using scanBuffer node that is
referencing a single bufferNode.

Release note: None

pkg/sql/buffer.go

@@ -0,0 +1,97 @@
+// Copyright 2019 The Cockroach Authors.
+//
+// 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,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+// implied. See the License for the specific language governing
+// permissions and limitations under the License.
+
+package sql
+
+import (
+	"context"
+
+	"github.com/cockroachdb/cockroach/pkg/sql/rowcontainer"
+	"github.com/cockroachdb/cockroach/pkg/sql/sem/tree"
+	"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
+)
+
+// bufferNode consumes its input one row at a time, stores it in the buffer,
+// and passes the row through. The buffered rows can be iterated over multiple
+// times.
+type bufferNode struct {
+	plan planNode
+
+	// TODO(yuzefovich): the buffer should probably be backed by disk. If so, the
+	// comments about TempStorage suggest that it should be used by DistSQL
+	// processors, but this node is local.
+	bufferedRows       *rowcontainer.RowContainer
+	passThruNextRowIdx int
+}
+
+func (n *bufferNode) startExec(params runParams) error {
+	n.bufferedRows = rowcontainer.NewRowContainer(
+		params.EvalContext().Mon.MakeBoundAccount(),
+		sqlbase.ColTypeInfoFromResCols(getPlanColumns(n.plan, false /* mut */)),
+		0, /* rowCapacity */
+	)
+	return nil
+}
+
+func (n *bufferNode) Next(params runParams) (bool, error) {
+	if err := params.p.cancelChecker.Check(); err != nil {
+		return false, err
+	}
+	ok, err := n.plan.Next(params)
+	if err != nil {
+		return false, err
+	}
+	if !ok {
+		return false, nil
+	}
+	if _, err = n.bufferedRows.AddRow(params.ctx, n.plan.Values()); err != nil {
+		return false, err
+	}
+	n.passThruNextRowIdx++
+	return true, nil
+}
+
+func (n *bufferNode) Values() tree.Datums {
+	return n.bufferedRows.At(n.passThruNextRowIdx - 1)
+}
+
+func (n *bufferNode) Close(ctx context.Context) {
+	n.plan.Close(ctx)
+	n.bufferedRows.Close(ctx)
+}
+
+// scanBufferNode behaves like an iterator into the bufferNode it is
+// referencing. The bufferNode can be iterated over multiple times
+// simultaneously, however, a new scanBufferNode is needed.
+type scanBufferNode struct {
+	buffer *bufferNode
+
+	nextRowIdx int
+}
+
+func (n *scanBufferNode) startExec(runParams) error {
+	return nil
+}
+
+func (n *scanBufferNode) Next(runParams) (bool, error) {
+	n.nextRowIdx++
+	return n.nextRowIdx <= n.buffer.bufferedRows.Len(), nil
+}
+
+func (n *scanBufferNode) Values() tree.Datums {
+	return n.buffer.bufferedRows.At(n.nextRowIdx - 1)
+}
+
+func (n *scanBufferNode) Close(context.Context) {
+}

pkg/sql/expand_plan.go

@@ -868,6 +868,9 @@ func (p *planner) simplifyOrderings(plan planNode, usefulOrdering sqlbase.Column
 	case *errorIfRowsNode:
 		n.plan = p.simplifyOrderings(n.plan, nil)
 
+	case *bufferNode:
+		n.plan = p.simplifyOrderings(n.plan, usefulOrdering)
+
 	case *valuesNode:
 	case *virtualTableNode:
 	case *alterIndexNode:
@@ -904,6 +907,7 @@ func (p *planner) simplifyOrderings(plan planNode, usefulOrdering sqlbase.Column
 	case *setZoneConfigNode:
 	case *showFingerprintsNode:
 	case *showTraceNode:
+	case *scanBufferNode:
 	case *scatterNode:
 
 	default:

pkg/sql/opt_filters.go

@@ -366,6 +366,11 @@ func (p *planner) propagateFilters(
 			return plan, extraFilter, err
 		}
 
+	case *bufferNode:
+		if n.plan, err = p.triggerFilterPropagation(ctx, n.plan); err != nil {
+			return plan, extraFilter, err
+		}
+
 	case *alterIndexNode:
 	case *alterTableNode:
 	case *alterSequenceNode:
@@ -401,6 +406,7 @@ func (p *planner) propagateFilters(
 	case *setZoneConfigNode:
 	case *showFingerprintsNode:
 	case *showTraceNode:
+	case *scanBufferNode:
 	case *scatterNode:
 
 	default:

pkg/sql/opt_limits.go

@@ -199,6 +199,9 @@ func (p *planner) applyLimit(plan planNode, numRows int64, soft bool) {
 	case *errorIfRowsNode:
 		p.setUnlimited(n.plan)
 
+	case *bufferNode:
+		p.setUnlimited(n.plan)
+
 	case *valuesNode:
 	case *virtualTableNode:
 	case *alterIndexNode:
@@ -237,6 +240,7 @@ func (p *planner) applyLimit(plan planNode, numRows int64, soft bool) {
 	case *showFingerprintsNode:
 	case *showTraceNode:
 	case *scatterNode:
+	case *scanBufferNode:
 
 	case *applyJoinNode, *lookupJoinNode, *zigzagJoinNode, *saveTableNode:
 		// These nodes are only planned by the optimizer.

pkg/sql/opt_needed.go

@@ -257,6 +257,9 @@ func setNeededColumns(plan planNode, needed []bool) {
 	case *errorIfRowsNode:
 		setNeededColumns(n.plan, allColumns(n.plan))
 
+	case *bufferNode:
+		setNeededColumns(n.plan, needed)
+
 	case *alterIndexNode:
 	case *alterTableNode:
 	case *alterSequenceNode:
@@ -293,6 +296,7 @@ func setNeededColumns(plan planNode, needed []bool) {
 	case *showFingerprintsNode:
 	case *showTraceNode:
 	case *scatterNode:
+	case *scanBufferNode:
 
 	default:
 		panic(fmt.Sprintf("unhandled node type: %T", plan))

pkg/sql/plan.go

@@ -165,6 +165,7 @@ type planNodeFastPath interface {
 var _ planNode = &alterIndexNode{}
 var _ planNode = &alterSequenceNode{}
 var _ planNode = &alterTableNode{}
+var _ planNode = &bufferNode{}
 var _ planNode = &cancelQueriesNode{}
 var _ planNode = &cancelSessionsNode{}
 var _ planNode = &createDatabaseNode{}
@@ -204,6 +205,7 @@ var _ planNode = &renameIndexNode{}
 var _ planNode = &renameTableNode{}
 var _ planNode = &renderNode{}
 var _ planNode = &rowCountNode{}
+var _ planNode = &scanBufferNode{}
 var _ planNode = &scanNode{}
 var _ planNode = &scatterNode{}
 var _ planNode = &serializeNode{}

pkg/sql/plan_columns.go

@@ -118,6 +118,8 @@ func getPlanColumns(plan planNode, mut bool) sqlbase.ResultColumns {
 
 	// Nodes that have the same schema as their source or their
 	// valueNode helper.
+	case *bufferNode:
+		return getPlanColumns(n.plan, mut)
 	case *distinctNode:
 		return getPlanColumns(n.plan, mut)
 	case *filterNode:
@@ -132,6 +134,8 @@ func getPlanColumns(plan planNode, mut bool) sqlbase.ResultColumns {
 		return getPlanColumns(n.source, mut)
 	case *saveTableNode:
 		return getPlanColumns(n.source, mut)
+	case *scanBufferNode:
+		return getPlanColumns(n.buffer, mut)
 
 	case *rowSourceToPlanNode:
 		return n.planCols

pkg/sql/plan_physical_props.go

@@ -93,6 +93,8 @@ func planPhysicalProps(plan planNode) physicalProps {
 	case *zigzagJoinNode:
 		return n.props
 	case *applyJoinNode:
+	case *bufferNode:
+	case *scanBufferNode:
 
 	// Every other node simply has no guarantees on its output rows.
 	case *CreateUserNode:

pkg/sql/walk.go

@@ -621,6 +621,9 @@ func (v *planVisitor) visitInternal(plan planNode, name string) {
 
 	case *errorIfRowsNode:
 		n.plan = v.visit(n.plan)
+
+	case *bufferNode:
+		n.plan = v.visit(n.plan)
 	}
 }
 
@@ -727,6 +730,7 @@ var planNodeNames = map[reflect.Type]string{
 	reflect.TypeOf(&alterTableNode{}):           "alter table",
 	reflect.TypeOf(&alterUserSetPasswordNode{}): "alter user",
 	reflect.TypeOf(&applyJoinNode{}):            "apply-join",
+	reflect.TypeOf(&bufferNode{}):               "buffer node",
 	reflect.TypeOf(&commentOnColumnNode{}):      "comment on column",
 	reflect.TypeOf(&commentOnDatabaseNode{}):    "comment on database",
 	reflect.TypeOf(&commentOnTableNode{}):       "comment on table",
@@ -773,6 +777,7 @@ var planNodeNames = map[reflect.Type]string{
 	reflect.TypeOf(&rowCountNode{}):             "count",
 	reflect.TypeOf(&rowSourceToPlanNode{}):      "row source to plan node",
 	reflect.TypeOf(&saveTableNode{}):            "save table",
+	reflect.TypeOf(&scanBufferNode{}):           "scan buffer node",
 	reflect.TypeOf(&scanNode{}):                 "scan",
 	reflect.TypeOf(&scatterNode{}):              "scatter",
 	reflect.TypeOf(&scrubNode{}):                "scrub",