func (mvcc *MVCC) putInternal(key Key, timestamp hlc.HLTimestamp, value []byte, txnID string) error {
keyMeta := &keyMetadata{}
ok, err := GetI(mvcc.engine, key, keyMeta)
if err != nil {
return err
}
// In case the key metadata exists.
if ok {
// There is an uncommitted write intent and the current Put
// operation does not come from the same transaction.
// This should not happen since range should check the existing
// write intent before executing any Put action at MVCC level.
if len(keyMeta.TxnID) > 0 && (len(txnID) == 0 || keyMeta.TxnID != txnID) {
return &writeIntentError{TxnID: keyMeta.TxnID}
}
if keyMeta.Timestamp.Less(timestamp) ||
(timestamp.Equal(keyMeta.Timestamp) && txnID == keyMeta.TxnID) {
// Update key metadata.
PutI(mvcc.engine, key, &keyMetadata{TxnID: txnID, Timestamp: timestamp})
} else {
// In case we receive a Put request to update an old version,
// it must be an error since raft should handle any client
// retry from timeout.
return &writeTimestampTooOldError{Timestamp: keyMeta.Timestamp}
}
} else { // In case the key metadata does not exist yet.
// Create key metadata.
PutI(mvcc.engine, key, &keyMetadata{TxnID: txnID, Timestamp: timestamp})
}
// Save the value with the given version (Key + Timestamp).
return mvcc.engine.Put(mvccEncodeKey(key, timestamp), value)
}
