code: @Override
    public LongWatermark getPreviousHighWatermark(Partition partition) {
      if (this.previousWatermarks.hasPartitionWatermarks(tableKey(partition.getTable()))) {
  
        // If partition has a watermark return.
        if (this.previousWatermarks.get(tableKey(partition.getTable())).containsKey(partitionKey(partition))) {
          return new LongWatermark(this.previousWatermarks.getPartitionWatermark(tableKey(partition.getTable()),
              partitionKey(partition)));
        }
      }
      return new LongWatermark(0);
  
    }
docs: Return the previous high watermark if found in previous state. Else returns 0
  {@inheritDoc}
  @see org.apache.gobblin.data.management.conversion.hive.watermarker.HiveSourceWatermarker#getPreviousHighWatermark(org.apache.hadoop.hive.ql.metadata.Partition)