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How can purge the deleted data?

  • January 5, 2016
  • 1 reply
  • 12 views
yin

I created a table and import some records.

then i deleted some data by 'delete from table_name where ...', last i deleted all data in this table.

But the superprojection's disk space can't be recycled.

I adjusted the parameters about the history retention and mergeout interval, and AHM has been now.

manual call purge or do_tm_task can release the disk space, and the space can't be recycled auto.

Can you tell what should I do?

 

thanks

Yin

    1 reply

    eli_revach
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    • eli_revach
    • Participating Frequently
    • January 5, 2016

    Hi

    Manage  deletes on Log-structured merge-tree  (LSM) storage engines (For my understanding Vertica  implement  kind of LSM method) is big headache  .  Vertica used delete vectors to optimized it.

    To reclaim your storage Mergeout  need to rebuild the ROS’s files that include the DV’s files you create during the delete operation . Mergeout   decide which ROS files to Merge using its internal  strata algorithm (http://www.slideshare.net/ZvikaGutkin/vertica-architecture ) , the idea is to reduce and minimize the amount of  times specific data set need to be merge  . Mergeout   will decide to Merge your DV’s  only when the amount of DV’s per stratum pass specific threshold     , in your case this probably the problem .

     

    Thanks 

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