[ACCUMULO-4011] Allow combiners reduce to return null

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Assignee: Unassigned
• Reporter: Keith Turner
• Created: 25/Sep/15 15:25
• Updated: 11/Jun/19 06:06

Description

Opening based on discussion from PR 47. If the reduce function in a combiner could return null to indicate that data should be dropped, this could offer a solution to ACCUMULO-2232.

For example assume someone was using a summing combiner and wanted to delete a column with a current value of 18. They could insert -18. If the combiner returned null when everything summed to 0, this would delete the row col. This method of deleting data would safe during partial compactions and would work correctly with new data being inserted after the -18 was inserted.

If this done, needs to be done in a way that is compatible with existing combiners.

Issue Links

• relates to: ACCUMULO-2232 Combiners can cause deleted data to come back