[ https://issues.apache.org/jira/browse/HIVE-4005?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Kevin Wilfong updated HIVE-4005: -------------------------------- Attachment: HIVE-4005.4.patch.txt > Column truncation > ----------------- > > Key: HIVE-4005 > URL: https://issues.apache.org/jira/browse/HIVE-4005 > Project: Hive > Issue Type: New Feature > Components: CLI > Affects Versions: 0.11.0 > Reporter: Kevin Wilfong > Assignee: Kevin Wilfong > Attachments: HIVE-4005.1.patch.txt, HIVE-4005.2.patch.txt, > HIVE-4005.3.patch.txt, HIVE-4005.4.patch.txt > > > Column truncation allows users to remove data for columns that are no longer > useful. > This is done by removing the data for the column and setting the length of > the column data and related lengths to 0 in the RC file header. > RC file was fixed to recognize columns with lengths of zero to be empty and > are treated as if the column doesn't exist in the data, a null is returned > for every value of that column in every row. This is the same thing that > happens when more columns are selected than exist in the file. > A new command was added to the CLI > TRUNCATE TABLE ... PARTITION ... COLUMNS ... > This launches a map only job where each mapper rewrites a single file without > the unnecessary column data and the adjusted headers. It does not > uncompress/deserialize the data so it is much faster than rewriting the data > with NULLs. -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira