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backfill.go
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backfill.go
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// Copyright 2015 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.
//
// Author: Tamir Duberstein (tamird@gmail.com)
package sql
import (
"sort"
"time"
"github.com/pkg/errors"
"golang.org/x/net/context"
"github.com/cockroachdb/cockroach/pkg/internal/client"
"github.com/cockroachdb/cockroach/pkg/roachpb"
"github.com/cockroachdb/cockroach/pkg/sql/distsqlrun"
"github.com/cockroachdb/cockroach/pkg/sql/parser"
"github.com/cockroachdb/cockroach/pkg/sql/sqlbase"
"github.com/cockroachdb/cockroach/pkg/util/log"
"github.com/cockroachdb/cockroach/pkg/util/timeutil"
)
const (
// TODO(vivek): Replace these constants with a runtime budget for the
// operation chunk involved.
// columnTruncateAndBackfillChunkSize is the maximum number of columns
// processed per chunk during column truncate or backfill.
columnTruncateAndBackfillChunkSize = 200
// indexTruncateChunkSize is the maximum number of index entries truncated
// per chunk during an index truncation. This value is larger than the
// other chunk constants because the operation involves only running a
// DeleteRange().
indexTruncateChunkSize = 600
// indexBackfillChunkSize is the maximum number index entries backfilled
// per chunk during an index backfill. The index backfill involves a table
// scan, and a number of individual ops presented in a batch. This value
// is smaller than ColumnTruncateAndBackfillChunkSize, because it involves
// a number of individual index row updates that can be scattered over
// many ranges.
indexBackfillChunkSize = 100
// checkpointInterval is the interval after which a checkpoint of the
// schema change is posted.
checkpointInterval = 10 * time.Second
)
var _ sort.Interface = columnsByID{}
var _ sort.Interface = indexesByID{}
type columnsByID []sqlbase.ColumnDescriptor
func (cds columnsByID) Len() int {
return len(cds)
}
func (cds columnsByID) Less(i, j int) bool {
return cds[i].ID < cds[j].ID
}
func (cds columnsByID) Swap(i, j int) {
cds[i], cds[j] = cds[j], cds[i]
}
type indexesByID []sqlbase.IndexDescriptor
func (ids indexesByID) Len() int {
return len(ids)
}
func (ids indexesByID) Less(i, j int) bool {
return ids[i].ID < ids[j].ID
}
func (ids indexesByID) Swap(i, j int) {
ids[i], ids[j] = ids[j], ids[i]
}
func (sc *SchemaChanger) getChunkSize(chunkSize int64) int64 {
if sc.testingKnobs.BackfillChunkSize > 0 {
return sc.testingKnobs.BackfillChunkSize
}
return chunkSize
}
// runBackfill runs the backfill for the schema changer.
func (sc *SchemaChanger) runBackfill(
ctx context.Context, lease *sqlbase.TableDescriptor_SchemaChangeLease, evalCtx parser.EvalContext,
) error {
if sc.testingKnobs.RunBeforeBackfill != nil {
if err := sc.testingKnobs.RunBeforeBackfill(); err != nil {
return err
}
}
if err := sc.ExtendLease(ctx, lease); err != nil {
return err
}
// Mutations are applied in a FIFO order. Only apply the first set of
// mutations. Collect the elements that are part of the mutation.
var droppedIndexDescs []sqlbase.IndexDescriptor
var addedIndexDescs []sqlbase.IndexDescriptor
// Indexes within the Mutations slice for checkpointing.
mutationSentinel := -1
var droppedIndexMutationIdx int
var tableDesc *sqlbase.TableDescriptor
if err := sc.db.Txn(ctx, func(ctx context.Context, txn *client.Txn) error {
var err error
tableDesc, err = sqlbase.GetTableDescFromID(ctx, txn, sc.tableID)
return err
}); err != nil {
return err
}
// Short circuit the backfill if the table has been deleted.
if tableDesc.Dropped() {
return nil
}
version := tableDesc.Version
log.VEventf(ctx, 0, "Running backfill for %q, v=%d, m=%d",
tableDesc.Name, tableDesc.Version, sc.mutationID)
needColumnBackfill := false
for i, m := range tableDesc.Mutations {
if m.MutationID != sc.mutationID {
break
}
switch m.Direction {
case sqlbase.DescriptorMutation_ADD:
switch t := m.Descriptor_.(type) {
case *sqlbase.DescriptorMutation_Column:
desc := m.GetColumn()
if desc.DefaultExpr != nil || !desc.Nullable {
needColumnBackfill = true
}
case *sqlbase.DescriptorMutation_Index:
addedIndexDescs = append(addedIndexDescs, *t.Index)
default:
return errors.Errorf("unsupported mutation: %+v", m)
}
case sqlbase.DescriptorMutation_DROP:
switch t := m.Descriptor_.(type) {
case *sqlbase.DescriptorMutation_Column:
needColumnBackfill = true
case *sqlbase.DescriptorMutation_Index:
droppedIndexDescs = append(droppedIndexDescs, *t.Index)
if droppedIndexMutationIdx == mutationSentinel {
droppedIndexMutationIdx = i
}
default:
return errors.Errorf("unsupported mutation: %+v", m)
}
}
}
// First drop indexes, then add/drop columns, and only then add indexes.
// Drop indexes.
if err := sc.truncateIndexes(
ctx, lease, version, droppedIndexDescs, droppedIndexMutationIdx,
); err != nil {
return err
}
// Add and drop columns.
if needColumnBackfill {
if err := sc.truncateAndBackfillColumns(ctx, evalCtx, lease, version); err != nil {
return err
}
}
// Add new indexes.
if len(addedIndexDescs) > 0 {
if err := sc.backfillIndexes(ctx, evalCtx, lease, version); err != nil {
return err
}
}
return nil
}
func (sc *SchemaChanger) maybeWriteResumeSpan(
ctx context.Context,
txn *client.Txn,
version sqlbase.DescriptorVersion,
resume roachpb.Span,
mutationIdx int,
lastCheckpoint *time.Time,
) error {
checkpointInterval := checkpointInterval
if sc.testingKnobs.WriteCheckpointInterval > 0 {
checkpointInterval = sc.testingKnobs.WriteCheckpointInterval
}
if timeutil.Since(*lastCheckpoint) < checkpointInterval {
return nil
}
tableDesc, err := sqlbase.GetTableDescFromID(ctx, txn, sc.tableID)
if err != nil {
return err
}
if tableDesc.Version != version {
return errors.Errorf("table version mismatch: %d, expected: %d", tableDesc.Version, version)
}
if len(tableDesc.Mutations[mutationIdx].ResumeSpans) > 0 {
tableDesc.Mutations[mutationIdx].ResumeSpans[0] = resume
} else {
tableDesc.Mutations[mutationIdx].ResumeSpans = append(tableDesc.Mutations[mutationIdx].ResumeSpans, resume)
}
if err := txn.SetSystemConfigTrigger(); err != nil {
return err
}
if err := txn.Put(
ctx,
sqlbase.MakeDescMetadataKey(tableDesc.GetID()),
sqlbase.WrapDescriptor(tableDesc),
); err != nil {
return err
}
*lastCheckpoint = timeutil.Now()
return nil
}
func (sc *SchemaChanger) getTableLease(
ctx context.Context, txn *client.Txn, lc *LeaseCollection, version sqlbase.DescriptorVersion,
) (*sqlbase.TableDescriptor, error) {
tableDesc, err := lc.getTableLeaseByID(ctx, txn, sc.tableID)
if err != nil {
return nil, err
}
if version != tableDesc.Version {
return nil, errors.Errorf("table version mismatch: %d, expected=%d", tableDesc.Version, version)
}
return tableDesc, nil
}
func (sc *SchemaChanger) truncateIndexes(
ctx context.Context,
lease *sqlbase.TableDescriptor_SchemaChangeLease,
version sqlbase.DescriptorVersion,
dropped []sqlbase.IndexDescriptor,
mutationIdx int,
) error {
chunkSize := sc.getChunkSize(indexTruncateChunkSize)
if sc.testingKnobs.BackfillChunkSize > 0 {
chunkSize = sc.testingKnobs.BackfillChunkSize
}
for _, desc := range dropped {
var resume roachpb.Span
lastCheckpoint := timeutil.Now()
for row, done := int64(0), false; !done; row += chunkSize {
// First extend the schema change lease.
if err := sc.ExtendLease(ctx, lease); err != nil {
return err
}
resumeAt := resume
if log.V(2) {
log.Infof(ctx, "drop index (%d, %d) at row: %d, span: %s",
sc.tableID, sc.mutationID, row, resume)
}
if err := sc.db.Txn(ctx, func(ctx context.Context, txn *client.Txn) error {
if sc.testingKnobs.RunBeforeBackfillChunk != nil {
if err := sc.testingKnobs.RunBeforeBackfillChunk(resume); err != nil {
return err
}
}
if sc.testingKnobs.RunAfterBackfillChunk != nil {
defer sc.testingKnobs.RunAfterBackfillChunk()
}
// TODO(vivek): See comment in backfillIndexesChunk.
if err := txn.SetSystemConfigTrigger(); err != nil {
return err
}
lc := &LeaseCollection{leaseMgr: sc.leaseMgr}
defer lc.releaseLeases(ctx)
tableDesc, err := sc.getTableLease(ctx, txn, lc, version)
if err != nil {
return err
}
rd, err := sqlbase.MakeRowDeleter(txn, tableDesc, nil, nil, false)
if err != nil {
return err
}
td := tableDeleter{rd: rd}
if err := td.init(txn); err != nil {
return err
}
resume, err = td.deleteIndex(
ctx, &desc, resumeAt, chunkSize,
)
if err != nil {
return err
}
if err := sc.maybeWriteResumeSpan(ctx, txn, version, resume, mutationIdx, &lastCheckpoint); err != nil {
return err
}
done = resume.Key == nil
return nil
}); err != nil {
return err
}
}
}
return nil
}
type backfillType int
const (
_ backfillType = iota
columnBackfill
indexBackfill
)
// getSpansToBackfill returns the spans that still have to be backfilled
// for the first mutation enqueued on the table descriptor that passes the
// input mutationFilter.
//
// Returns nil if the backfill is complete (mutation no longer exists or there
// are no "ResumeSpans").
func (sc *SchemaChanger) getSpansToBackfill(
ctx context.Context, filter distsqlrun.MutationFilter,
) ([]roachpb.Span, error) {
var spans []roachpb.Span
err := sc.db.Txn(ctx, func(ctx context.Context, txn *client.Txn) error {
spans = nil
tableDesc, err := sqlbase.GetTableDescFromID(ctx, txn, sc.tableID)
if err != nil {
return err
}
if len(tableDesc.Mutations) > 0 {
mutationID := tableDesc.Mutations[0].MutationID
for _, m := range tableDesc.Mutations {
if m.MutationID != mutationID {
break
}
if filter(m) {
spans = m.ResumeSpans
break
}
}
}
return nil
})
return spans, err
}
// distBackfill runs (or continues) a backfill for the first mutation
// enqueued on the SchemaChanger's table descriptor that passes the input
// MutationFilter.
func (sc *SchemaChanger) distBackfill(
ctx context.Context,
evalCtx parser.EvalContext,
lease *sqlbase.TableDescriptor_SchemaChangeLease,
version sqlbase.DescriptorVersion,
backfillType backfillType,
backfillChunkSize int64,
filter distsqlrun.MutationFilter,
) error {
duration := checkpointInterval
if sc.testingKnobs.WriteCheckpointInterval > 0 {
duration = sc.testingKnobs.WriteCheckpointInterval
}
chunkSize := sc.getChunkSize(backfillChunkSize)
for {
// Repeat until getSpansToBackfill returns no spans, indicating that the
// backfill is complete.
spans, err := sc.getSpansToBackfill(ctx, filter)
if err != nil {
return err
}
if len(spans) <= 0 {
break
}
if err := sc.ExtendLease(ctx, lease); err != nil {
return err
}
log.VEventf(ctx, 2, "backfill: process %+v spans", spans)
if err := sc.db.Txn(ctx, func(ctx context.Context, txn *client.Txn) error {
lc := &LeaseCollection{leaseMgr: sc.leaseMgr}
// Use a leased table descriptor for the backfill.
defer lc.releaseLeases(ctx)
tableDesc, err := sc.getTableLease(ctx, txn, lc, version)
if err != nil {
return err
}
// otherTableDescs contains any other table descriptors required by the
// backfiller processor.
var otherTableDescs []sqlbase.TableDescriptor
if backfillType == columnBackfill {
fkTables := sqlbase.TablesNeededForFKs(*tableDesc, sqlbase.CheckUpdates)
for k := range fkTables {
table, err := lc.getTableLeaseByID(ctx, txn, k)
if err != nil {
return err
}
otherTableDescs = append(otherTableDescs, *table)
}
}
// TODO(andrei): pass the right caches. I think this will crash without
// them.
recv, err := makeDistSQLReceiver(
ctx,
nil, /* sink */
nil, /* rangeCache */
nil, /* leaseCache */
nil, /* txn - the flow does not run wholly in a txn */
// updateClock - the flow will not generate errors with time signal.
// TODO(andrei): plumb a clock update handler here regardless of whether
// it will actually be used or not.
nil,
)
if err != nil {
return err
}
planCtx := sc.distSQLPlanner.NewPlanningCtx(ctx, txn)
plan, err := sc.distSQLPlanner.CreateBackfiller(
&planCtx, backfillType, *tableDesc, duration, chunkSize, spans, otherTableDescs,
)
if err != nil {
return err
}
if err := sc.distSQLPlanner.Run(&planCtx, txn, &plan, &recv, evalCtx); err != nil {
return err
}
return recv.err
}); err != nil {
return err
}
}
return nil
}
func (sc *SchemaChanger) backfillIndexes(
ctx context.Context,
evalCtx parser.EvalContext,
lease *sqlbase.TableDescriptor_SchemaChangeLease,
version sqlbase.DescriptorVersion,
) error {
return sc.distBackfill(
ctx, evalCtx, lease, version, indexBackfill, indexBackfillChunkSize,
distsqlrun.IndexMutationFilter)
}
func (sc *SchemaChanger) truncateAndBackfillColumns(
ctx context.Context,
evalCtx parser.EvalContext,
lease *sqlbase.TableDescriptor_SchemaChangeLease,
version sqlbase.DescriptorVersion,
) error {
return sc.distBackfill(
ctx, evalCtx,
lease, version, columnBackfill, columnTruncateAndBackfillChunkSize,
distsqlrun.ColumnMutationFilter)
}