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Merge pull request #7872 from heyitsanthony/break-boltdb-lock-readtx

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backend: don't hold boltdb read txn lock on cursor scanning
This commit is contained in:
Anthony Romano 2017-05-26 10:25:33 -07:00 committed by GitHub
commit 3e1eb1a2e7
2 changed files with 18 additions and 7 deletions
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21
mvcc/backend/batch_tx.go
View File

@ -45,6 +45,13 @@ type batchTx struct {
pending int
}
var nopLock sync.Locker = &nopLocker{}
type nopLocker struct{}
func (*nopLocker) Lock() {}
func (*nopLocker) Unlock() {}
func (t *batchTx) UnsafeCreateBucket(name []byte) {
_, err := t.tx.CreateBucket(name)
if err != nil && err != bolt.ErrBucketExists {
@ -81,28 +88,34 @@ func (t *batchTx) unsafePut(bucketName []byte, key []byte, value []byte, seq boo
// UnsafeRange must be called holding the lock on the tx.
func (t *batchTx) UnsafeRange(bucketName, key, endKey []byte, limit int64) ([][]byte, [][]byte) {
k, v, err := unsafeRange(t.tx, bucketName, key, endKey, limit)
// nop lock since a write txn should already hold a lock over t.tx
k, v, err := unsafeRange(t.tx, bucketName, key, endKey, limit, nopLock)
if err != nil {
plog.Fatal(err)
}
return k, v
}
func unsafeRange(tx *bolt.Tx, bucketName, key, endKey []byte, limit int64) (keys [][]byte, vs [][]byte, err error) {
func unsafeRange(tx *bolt.Tx, bucketName, key, endKey []byte, limit int64, l sync.Locker) (keys [][]byte, vs [][]byte, err error) {
l.Lock()
bucket := tx.Bucket(bucketName)
if bucket == nil {
l.Unlock()
return nil, nil, fmt.Errorf("bucket %s does not exist", bucketName)
}
if len(endKey) == 0 {
if v := bucket.Get(key); v != nil {
v := bucket.Get(key)
l.Unlock()
if v != nil {
return append(keys, key), append(vs, v), nil
}
return nil, nil, nil
}
c := bucket.Cursor()
l.Unlock()
if limit <= 0 {
limit = math.MaxInt64
}
c := bucket.Cursor()
for ck, cv := c.Seek(key); ck != nil && bytes.Compare(ck, endKey) < 0; ck, cv = c.Next() {
vs = append(vs, cv)
keys = append(keys, ck)

4
mvcc/backend/read_tx.go
View File

@ -63,10 +63,8 @@ func (rt *readTx) UnsafeRange(bucketName, key, endKey []byte, limit int64) ([][]
if int64(len(keys)) == limit {
return keys, vals
}
rt.txmu.Lock()
// ignore error since bucket may have been created in this batch
k2, v2, _ := unsafeRange(rt.tx, bucketName, key, endKey, limit-int64(len(keys)))
rt.txmu.Unlock()
k2, v2, _ := unsafeRange(rt.tx, bucketName, key, endKey, limit-int64(len(keys)), &rt.txmu)
return append(k2, keys...), append(v2, vals...)
}