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TransactionBatch is used to write a series of transactions. There is one file created on HDFS per TxnBatch in each bucket. The API examines each record to decide which bucket it belongs to and writes it to the appropriate bucket. If the table has 5 buckets, there will be 5 files (some of them could be empty) for the TxnBatch (before compaction kicks in).  Prior to Hive 1.3.0, a bug in the API's bucket computation logic caused incorrect distribution of records into buckets, which could lead to incorrect data returned from queries using bucket join algorithms.

For each transaction in the TxnBatch, the application calls beginNextTransaction, write, and then commit or abort as appropriate. See the Javadoc for details. All records in a single Transaction Batch will go to the same bucket. 

Transactions in a TransactionBatch are eventually expired by the Metastore if not committed or aborted after hive.txn.timeout secs. TrasnactionBatch class provides a heartbeat() method to prolong the lifetime of unused transactions in the batch.

Note: Hive 1.3.0 onwards, invoking TxnBatch.close() will cause all unused transaction in the current TxnBatch to be aborted.

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