Modify the CarbonData Table

SET and UNSET

When the SET command is executed, the new properties overwrite the existing ones.

• SORT SCOPE

  The following is an example of the SET SORT SCOPE command:

  ALTER TABLE tablename SET TBLPROPERTIES('SORT_SCOPE'='no_sort')

  After running the UNSET SORT SCOPE command, the default value NO_SORT is adopted.

  The following is an example of the UNSET SORT SCOPE command:

  ALTER TABLE tablename UNSET TBLPROPERTIES('SORT_SCOPE')

• SORT COLUMNS

  The following is an example of the SET SORT COLUMNS command:

  ALTER TABLE tablename SET TBLPROPERTIES('SORT_COLUMNS'='column1')

  After this command is executed, the new value of SORT_COLUMNS is used. Users can adjust the SORT_COLUMNS based on the query results, but the original data is not affected. The operation does not affect the query performance of the original data segments which are not sorted by new SORT_COLUMNS.

  The UNSET command is not supported, but the SORT_COLUMNS can be set to empty string instead of using the UNSET command.

  ALTER TABLE tablename SET TBLPROPERTIES('SORT_COLUMNS'='')

  

  • The later version will enhance custom compaction to resort the old segments.
  • The value of SORT_COLUMNS cannot be modified in the streaming table.
  • If the inverted index column is removed from SORT_COLUMNS, inverted index will not be created in this column. However, the old configuration of INVERTED_INDEX will be kept.