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A new command ABORT TRANSACTIONS has been added, see ABORT TRANSACTIONS for Abort Transactions for details.

Basic Design

HDFS does not support in-place changes to files.  It also does not offer read consistency in the face of writers appending to files being read by a user.  In order to provide these features on top of HDFS we have followed the standard approach used in other data warehousing tools.  Data for the table or partition is stored in a set of base files.  New records, updates, and deletes are stored in delta files.  A new set of delta files is created for each transaction (or in the case of streaming agents such as Flume or Storm, each batch of transactions) that alters a table or partition.  At read time the reader merges the base and delta files, applying any updates and deletes as it reads.

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