keith-turner commented on issue #811: Look into adding API operation to return non existant row columns. URL: https://github.com/apache/fluo/issues/811#issuecomment-340561296 This is a very rough outline of what I think needs to be done for this feature. * Add `setIfAbsent(Bytes row, Column col, Value val)` method to TransactionBase interface. * Implement `setIfAbsent(Bytes row, Column col, Value val)` in TransactionImpl. This method could call `set(Bytes row, Column col, Value val)` with a special value that indicates this row+col is expected to be empty. This is similar to what delete does internally, [delete calls set with a special value](https://github.com/apache/fluo/blob/rel/fluo-1.1.0-incubating/modules/core/src/main/java/org/apache/fluo/core/impl/TransactionImpl.java#L337). * In the [prewrite phase](https://github.com/apache/fluo/blob/rel/fluo-1.1.0-incubating/modules/core/src/main/java/org/apache/fluo/core/impl/TransactionImpl.java#L340) of `commit()` when a transaction sets its locks, I think a condition can be added to the conditional mutation used for locks. This condition could configure the snapshot iterator and expect the result to be empty. Some background on conditional mutations : http://rleary.com/blog/accumulo-conditional-mutations/
---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
