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Fix Txn too big error in bulk loader #3998

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Fix Txn too big error in bulk loader #3998

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c982037
Fix Txn too big error in bulk loader
ashish-goswami Sep 16, 2019
1d350df
Address review comments
ashish-goswami Sep 18, 2019
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42 changes: 33 additions & 9 deletions dgraph/cmd/bulk/reduce.go
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Original file line number Diff line number Diff line change
Expand Up @@ -39,22 +39,38 @@ func (r *reducer) run() {
thr.Start()
NumReducers.Add(1)
NumQueuedReduceJobs.Add(-1)
r.writesThr.Start()
go func(job shuffleOutput) {
r.reduce(job)
thr.Done()
NumReducers.Add(-1)
}(reduceJob)
}
thr.Wait()
// We should wait for all pending transactions to commit here. In this function we are not
// calling r.writesThr.Start(), but those are called as part of r.reduce(job) function.
r.writesThr.Wait()
}

func (r *reducer) reduce(job shuffleOutput) {
var currentKey []byte
var uids []uint64
pl := new(pb.PostingList)
txn := job.db.NewTransactionAt(r.state.writeTs, true)

newTxn := func() *badger.Txn {
r.writesThr.Start()
return job.db.NewTransactionAt(r.state.writeTs, true)
}

commitTxn := func(txn *badger.Txn) {
NumBadgerWrites.Add(1)
x.Check(txn.CommitAt(r.state.writeTs, func(err error) {
x.Check(err)
NumBadgerWrites.Add(-1)
r.writesThr.Done()
}))
}

txn := newTxn()

outputPostingList := func() {
atomic.AddInt64(&r.prog.reduceKeyCount, 1)
Expand All @@ -68,7 +84,20 @@ func (r *reducer) reduce(job shuffleOutput) {
pl.Pack = codec.Encode(uids, 256)
val, err := pl.Marshal()
x.Check(err)
x.Check(txn.SetEntry(badger.NewEntry(currentKey, val).WithMeta(meta)))

// If error returned while setting entry is badger.ErrTxnTooBig, we should commit current
// txn and start a new one. But if setEntry returns same error on new Txn, that means
// entry size is bigger than maximum size Txn can have. Hence we should panic.
e := badger.NewEntry(currentKey, val).WithMeta(meta)
err = txn.SetEntry(e)
if err == badger.ErrTxnTooBig {
commitTxn(txn)

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@hackerone-code hackerone-code Bot Sep 16, 2019

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This extra newline doesn't seem necessary

txn = newTxn()
x.Check(txn.SetEntry(e)) // We are not checking ErrTxnTooBig the second time.
} else {
x.Check(err)
}

uids = uids[:0]
pl.Reset()
Expand Down Expand Up @@ -96,10 +125,5 @@ func (r *reducer) reduce(job shuffleOutput) {
}
outputPostingList()

NumBadgerWrites.Add(1)
x.Check(txn.CommitAt(r.state.writeTs, func(err error) {
x.Check(err)
NumBadgerWrites.Add(-1)
r.writesThr.Done()
}))
commitTxn(txn)
}
14 changes: 13 additions & 1 deletion dgraph/cmd/bulk/schema.go
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Original file line number Diff line number Diff line change
Expand Up @@ -128,7 +128,19 @@ func (s *schemaStore) write(db *badger.DB, preds []string) {
k := x.SchemaKey(pred)
v, err := sch.Marshal()
x.Check(err)
x.Check(txn.SetEntry(badger.NewEntry(k, v).WithMeta(posting.BitCompletePosting)))

// If error returned while setting entry is badger.ErrTxnTooBig, we should commit current
// txn and start a new one. But if setEntry returns same error on new Txn, that means
// entry size is bigger than maximum size Txn can have. Hence we should panic.
e := badger.NewEntry(k, v).WithMeta(posting.BitCompletePosting)
err = txn.SetEntry(e)
if err == badger.ErrTxnTooBig {
x.Check(txn.CommitAt(1, nil))
txn = db.NewTransactionAt(math.MaxUint64, true)
x.Check(txn.SetEntry(e)) // We are not checking ErrTxnTooBig for second time.
} else {
x.Check(err)
}
}

// Write schema always at timestamp 1, s.state.writeTs may not be equal to 1
Expand Down