Compaction of Data in FULL ACID Transactional Table
As administrator, you need to manage compaction of delta files that accumulate during data ingestion. Compaction is a process that performs critical housekeeping of files.
Hive creates a set of delta files for each transaction that alters a table or partition and stores them in a separate delta directory. When the number of delta and delete directories in the table grow, the read performance will be impacted, since reading is a process of merging the results of valid transactions. To avoid any compromise on the read performance, occasionally Hive performs compaction, namely minor and major. This process merges these directories while preserving the transaction information.
For more information, see Data Compaction.