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tablereader.go
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tablereader.go
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// Copyright 2016 The Cockroach Authors.
//
// Use of this software is governed by the Business Source License
// included in the file licenses/BSL.txt.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0, included in the file
// licenses/APL.txt.
package rowexec
import (
"context"
"fmt"
"sync"
"time"
"github.com/cockroachdb/cockroach/pkg/roachpb"
"github.com/cockroachdb/cockroach/pkg/sql/execinfra"
"github.com/cockroachdb/cockroach/pkg/sql/execinfrapb"
"github.com/cockroachdb/cockroach/pkg/sql/row"
"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
"github.com/cockroachdb/cockroach/pkg/util/humanizeutil"
"github.com/cockroachdb/cockroach/pkg/util/log"
"github.com/cockroachdb/cockroach/pkg/util/tracing"
"github.com/opentracing/opentracing-go"
"github.com/pkg/errors"
)
// tableReader is the start of a computation flow; it performs KV operations to
// retrieve rows for a table, runs a filter expression, and passes rows with the
// desired column values to an output RowReceiver.
// See docs/RFCS/distributed_sql.md
type tableReader struct {
execinfra.ProcessorBase
spans roachpb.Spans
limitHint int64
// maxResults is non-zero if there is a limit on the total number of rows
// that the tableReader will read.
maxResults uint64
// See TableReaderSpec.MaxTimestampAgeNanos.
maxTimestampAge time.Duration
ignoreMisplannedRanges bool
// fetcher wraps a row.Fetcher, allowing the tableReader to add a stat
// collection layer.
fetcher execinfra.RowFetcher
alloc sqlbase.DatumAlloc
// rowsRead is the number of rows read and is tracked unconditionally.
rowsRead int64
}
var _ execinfra.Processor = &tableReader{}
var _ execinfra.RowSource = &tableReader{}
var _ execinfrapb.MetadataSource = &tableReader{}
const tableReaderProcName = "table reader"
var trPool = sync.Pool{
New: func() interface{} {
return &tableReader{}
},
}
// newTableReader creates a tableReader.
func newTableReader(
flowCtx *execinfra.FlowCtx,
processorID int32,
spec *execinfrapb.TableReaderSpec,
post *execinfrapb.PostProcessSpec,
output execinfra.RowReceiver,
) (*tableReader, error) {
if flowCtx.NodeID == 0 {
return nil, errors.Errorf("attempting to create a tableReader with uninitialized NodeID")
}
tr := trPool.Get().(*tableReader)
tr.limitHint = execinfra.LimitHint(spec.LimitHint, post)
tr.maxResults = spec.MaxResults
tr.maxTimestampAge = time.Duration(spec.MaxTimestampAgeNanos)
returnMutations := spec.Visibility == execinfrapb.ScanVisibility_PUBLIC_AND_NOT_PUBLIC
types := spec.Table.ColumnTypesWithMutations(returnMutations)
tr.ignoreMisplannedRanges = flowCtx.Local
if err := tr.Init(
tr,
post,
types,
flowCtx,
processorID,
output,
nil, /* memMonitor */
execinfra.ProcStateOpts{
// We don't pass tr.input as an inputToDrain; tr.input is just an adapter
// on top of a Fetcher; draining doesn't apply to it. Moreover, Andrei
// doesn't trust that the adapter will do the right thing on a Next() call
// after it had previously returned an error.
InputsToDrain: nil,
TrailingMetaCallback: tr.generateTrailingMeta,
},
); err != nil {
return nil, err
}
neededColumns := tr.Out.NeededColumns()
var fetcher row.Fetcher
columnIdxMap := spec.Table.ColumnIdxMapWithMutations(returnMutations)
if _, _, err := execinfra.InitRowFetcher(
&fetcher, &spec.Table, int(spec.IndexIdx), columnIdxMap, spec.Reverse,
neededColumns, spec.IsCheck, &tr.alloc, spec.Visibility,
); err != nil {
return nil, err
}
nSpans := len(spec.Spans)
if cap(tr.spans) >= nSpans {
tr.spans = tr.spans[:nSpans]
} else {
tr.spans = make(roachpb.Spans, nSpans)
}
for i, s := range spec.Spans {
tr.spans[i] = s.Span
}
if sp := opentracing.SpanFromContext(flowCtx.EvalCtx.Ctx()); sp != nil && tracing.IsRecording(sp) {
tr.fetcher = execinfra.NewRowFetcherStatCollector(&fetcher)
tr.FinishTrace = tr.outputStatsToTrace
} else {
tr.fetcher = &fetcher
}
return tr, nil
}
func (tr *tableReader) generateTrailingMeta(ctx context.Context) []execinfrapb.ProducerMetadata {
trailingMeta := tr.generateMeta(ctx)
tr.InternalClose()
return trailingMeta
}
// Start is part of the RowSource interface.
func (tr *tableReader) Start(ctx context.Context) context.Context {
if tr.FlowCtx.Txn == nil {
log.Fatalf(ctx, "tableReader outside of txn")
}
ctx = tr.StartInternal(ctx, tableReaderProcName)
limitBatches := execinfra.ScanShouldLimitBatches(tr.maxResults, tr.limitHint, tr.FlowCtx)
log.VEventf(ctx, 1, "starting scan with limitBatches %t", limitBatches)
var err error
if tr.maxTimestampAge == 0 {
err = tr.fetcher.StartScan(
ctx, tr.FlowCtx.Txn, tr.spans,
limitBatches, tr.limitHint, tr.FlowCtx.TraceKV,
)
} else {
initialTS := tr.FlowCtx.Txn.GetTxnCoordMeta(ctx).Txn.ReadTimestamp
err = tr.fetcher.StartInconsistentScan(
ctx, tr.FlowCtx.Cfg.DB, initialTS,
tr.maxTimestampAge, tr.spans,
limitBatches, tr.limitHint, tr.FlowCtx.TraceKV,
)
}
if err != nil {
tr.MoveToDraining(err)
}
return ctx
}
// Release releases this tableReader back to the pool.
func (tr *tableReader) Release() {
tr.ProcessorBase.Reset()
tr.fetcher.Reset()
*tr = tableReader{
ProcessorBase: tr.ProcessorBase,
fetcher: tr.fetcher,
spans: tr.spans[:0],
rowsRead: 0,
}
trPool.Put(tr)
}
// Next is part of the RowSource interface.
func (tr *tableReader) Next() (sqlbase.EncDatumRow, *execinfrapb.ProducerMetadata) {
for tr.State == execinfra.StateRunning {
row, _, _, err := tr.fetcher.NextRow(tr.Ctx)
if row == nil || err != nil {
tr.MoveToDraining(err)
break
}
// When tracing is enabled, number of rows read is tracked twice (once
// here, and once through InputStats). This is done so that non-tracing
// case can avoid tracking of the stall time which gives a noticeable
// performance hit.
tr.rowsRead++
if outRow := tr.ProcessRowHelper(row); outRow != nil {
return outRow, nil
}
}
return nil, tr.DrainHelper()
}
// ConsumerClosed is part of the RowSource interface.
func (tr *tableReader) ConsumerClosed() {
// The consumer is done, Next() will not be called again.
tr.InternalClose()
}
var _ execinfrapb.DistSQLSpanStats = &TableReaderStats{}
const tableReaderTagPrefix = "tablereader."
// Stats implements the SpanStats interface.
func (trs *TableReaderStats) Stats() map[string]string {
inputStatsMap := trs.InputStats.Stats(tableReaderTagPrefix)
inputStatsMap[tableReaderTagPrefix+execinfra.BytesReadTagSuffix] = humanizeutil.IBytes(trs.BytesRead)
return inputStatsMap
}
// StatsForQueryPlan implements the DistSQLSpanStats interface.
func (trs *TableReaderStats) StatsForQueryPlan() []string {
return append(
trs.InputStats.StatsForQueryPlan("" /* prefix */),
fmt.Sprintf("%s: %s", execinfra.BytesReadQueryPlanSuffix, humanizeutil.IBytes(trs.BytesRead)),
)
}
// outputStatsToTrace outputs the collected tableReader stats to the trace. Will
// fail silently if the tableReader is not collecting stats.
func (tr *tableReader) outputStatsToTrace() {
is, ok := execinfra.GetFetcherInputStats(tr.FlowCtx, tr.fetcher)
if !ok {
return
}
if sp := opentracing.SpanFromContext(tr.Ctx); sp != nil {
tracing.SetSpanStats(sp, &TableReaderStats{
InputStats: is,
BytesRead: tr.fetcher.GetBytesRead(),
})
}
}
func (tr *tableReader) generateMeta(ctx context.Context) []execinfrapb.ProducerMetadata {
var trailingMeta []execinfrapb.ProducerMetadata
if !tr.ignoreMisplannedRanges {
ranges := execinfra.MisplannedRanges(ctx, tr.fetcher.GetRangesInfo(), tr.FlowCtx.NodeID)
if ranges != nil {
trailingMeta = append(trailingMeta, execinfrapb.ProducerMetadata{Ranges: ranges})
}
}
if meta := execinfra.GetTxnCoordMeta(ctx, tr.FlowCtx.Txn); meta != nil {
trailingMeta = append(trailingMeta, execinfrapb.ProducerMetadata{TxnCoordMeta: meta})
}
meta := execinfrapb.GetProducerMeta()
meta.Metrics = execinfrapb.GetMetricsMeta()
meta.Metrics.BytesRead, meta.Metrics.RowsRead = tr.fetcher.GetBytesRead(), tr.rowsRead
trailingMeta = append(trailingMeta, *meta)
return trailingMeta
}
// DrainMeta is part of the MetadataSource interface.
func (tr *tableReader) DrainMeta(ctx context.Context) []execinfrapb.ProducerMetadata {
return tr.generateMeta(ctx)
}