private void seekToNextKeyBuffer() throws IOException {
      if (!keyInit) {
        return;
      }
      if (!currentValue.inited) {
        in.skip(currentRecordLength - currentKeyLength);
      }
    }
Read and return the next record length, potentially skipping over a sync
block.

@return the length of the next record or -1 if there is no next record
@throws IOException
ql/src/java/org/apache/hadoop/hive/ql/io/RCFile.java