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A new option has been added to ALTER TABLE to request a compaction of a table or partition.  In general users do not need to request compactions, as the system will detect the need for them and initiate the compaction.  However, if compaction is turned off for a table or a user wants to compact the table at a time the system would not choose to, ALTER TABLE can be used to initiate the compaction.  See Alter Table/Partition Compact for details.  This will enqueue a request for compaction and return.  To watch the progress of the compaction the user can use SHOW COMPACTIONS.

A new command ABORT TRANSACTIONS has been added to remove the specified transaction records from the Hive metastore, starting in Hive 2.1.

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