Releasing the space created by deletion of rows from table on greenplum

Question

I have a table on greenplum from which data is being deleted on a daily basis using a simple delete statement. However, the size of the table is not decreasing. Is there some way using which the space returned by deletion of rows is removed from the table and thus size of the table be reduced.

Answer 1

Greenplum database at it's core uses much of the same code as a Postgres database. Therefore, the command you want is the VACUUM command. From the docs at http://gpdb.docs.gopivotal.com/4300/pdf/GPDB43RefGuide.pdf:

VACUUM reclaims storage occupied by deleted tuples. In normal Greenplum Database operation, tuples that are deleted or obsoleted by an update are not physically removed from their table; they remain present on disk until a VACUUM is done. Therefore it is necessary to do VACUUM periodically, especially on frequently-updated tables.

Also, if you are altering a significant number of rows, then you may want to use VACUUM ANALYZE to allow the statistics for the table to be updated for better query planning.