I am trying to parse out the bitcoin data using Big Data and wanted to know more about the blk files themselves. I was wondering how does bitcoin split the transactions across the files. I know there is a 128 MiB limit on the files. Does that mean it is possible for transaction data to be split across a blk ? For instance the merkle root of the transaction is in one file and the output index is in another ? Or is block data retained in a single file ?