// Get looks up the latest sequence number recorded for this transaction ID.
// The latest entry is that with the highest epoch (and then, highest
// sequence). On a miss, zero is returned for both. If an entry is found and a
// SequenceCacheEntry is provided, it is populated from the found value.
func (sc *SequenceCache) Get(e engine.Engine, txnID *uuid.UUID, dest *roachpb.SequenceCacheEntry) (uint32, uint32, error) {
if txnID == nil {
return 0, 0, errEmptyTxnID
}
// Pull response from disk and read into reply if available. Sequence
// number sorts in decreasing order, so this gives us the largest entry or
// an entry which isn't ours. To avoid encoding an end key for the scan,
// we just scan and check via a simple prefix check whether we read a
// key for "our" cache id.
prefix := keys.SequenceCacheKeyPrefix(sc.rangeID, txnID)
kvs, _, err := engine.MVCCScan(e, prefix, sc.max, 1, /* num */
roachpb.ZeroTimestamp, true /* consistent */, nil /* txn */)
if err != nil || len(kvs) == 0 || !bytes.HasPrefix(kvs[0].Key, prefix) {
return 0, 0, err
}
_, epoch, seq, err := keys.DecodeSequenceCacheKey(kvs[0].Key, sc.scratchBuf[:0])
if err != nil {
return 0, 0, err
}
if dest != nil {
dest.Reset()
// Caller wants to have the unmarshaled value.
if err := kvs[0].Value.GetProto(dest); err != nil {
return 0, 0, err
}
}
return epoch, seq, nil
}
func trySequence(kv engine.MVCCKeyValue) (string, error) {
if kv.Key.Timestamp != roachpb.ZeroTimestamp {
return "", errors.New("not a sequence cache key")
}
_, _, _, err := keys.DecodeSequenceCacheKey(kv.Key.Key, nil)
if err != nil {
return "", err
}
var dest roachpb.SequenceCacheEntry
if err := maybeUnmarshalInline(kv.Value, &dest); err != nil {
return "", err
}
return fmt.Sprintf("ts=%s, key=%q\n", dest.Timestamp, dest.Key), nil
}
// Iterate walks through the sequence cache, invoking the given callback for
// each unmarshaled entry with the key, the transaction ID and the decoded
// entry.
func (sc *SequenceCache) Iterate(e engine.Engine, f func([]byte, *uuid.UUID, roachpb.SequenceCacheEntry)) {
_, _ = engine.MVCCIterate(e, sc.min, sc.max, roachpb.ZeroTimestamp,
true /* consistent */, nil /* txn */, false, /* !reverse */
func(kv roachpb.KeyValue) (bool, error) {
var entry roachpb.SequenceCacheEntry
txnID, _, _, err := keys.DecodeSequenceCacheKey(kv.Key, nil)
if err != nil {
panic(err) // TODO(tschottdorf): ReplicaCorruptionError
}
if err := kv.Value.GetProto(&entry); err != nil {
panic(err) // TODO(tschottdorf): ReplicaCorruptionError
}
f(kv.Key, txnID, entry)
return false, nil
})
}
func decodeSequenceCacheMVCCKey(encKey engine.MVCCKey, dest []byte) (*uuid.UUID, uint32, uint32, error) {
if encKey.IsValue() {
return nil, 0, 0, util.Errorf("key %s is not a raw MVCC value", encKey)
}
return keys.DecodeSequenceCacheKey(encKey.Key, dest)
}