[SOLR-8337] Add ReduceOperation and wire it into the ReducerStream

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Assignee: Unassigned
• Reporter: Joel Bernstein
• Created: 24/Nov/15 19:51
• Updated: 08/Oct/19 14:50
• Resolved: 11/Dec/15 02:33

Description

The current ReducerStream groups all documents that share the same key(s) into a list and emits a single Tuple that contains this list. There is no way to tell the ReducerStream to do something more interesting with groups, for example summing a column within a group, or joining tuples.

This ticket adds a new type of operation called a ReduceOperation which is passed to the ReducerStream so that the reduce behavior can be specialized.

The ReduceOperation has two methods:

1) operate(Tuple) : This is called once for each Tuple in a group. This method can be used to aggregate Tuples as they added to a group.
2) reduce() : This is called when the group keys change. This method returns a single Tuple which is output by the ReducerStream. The ReduceOperation must clear it's internal structures when reduce is called as well, to prepare for the next group.

Issue Links

• is related to: SOLR-8125 Umbrella ticket for Streaming and SQL issues