[TAJO-742] (Umbrella) Theta join support

• Type: Improvement
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Component/s: Physical Operator
• Assignee: Unassigned
• Reporter: JaeHwa Jung
• Created: 08/Apr/14 13:42
• Updated: 17/Jul/14 02:52

Description

Currently, Tajo supports only equi-join. In contrast, theta-joins (not equality join) are used in many real applications. We need to support theta-joins in Tajo.

If a join condition includes anything other than equality predicate "=", we call the join theta join. The predicates can be as follows:

• >, >=, <, <=, !=, LIKE. RLIKE, ...

Basically, some predicates can exploit hash shuffle, range shuffle, or other thing. Other predicates requires that only one node processes all intermediate data by using BNL. Also, if a join condition is a mixed of equi-join and theta-join conditions, this join can make use of hash shuffle. This issue requires some investigation.

This is an umbrella issue. We'll create subtasks.

Sub-Tasks

• Implement hash-theta join: Open