[JENA-1023] Algebra execution join library

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: Jena 3.0.1
• Component/s: ARQ
• Assignee: Andy Seaborne
• Reporter: Andy Seaborne
• Created: 07/Sep/15 18:07
• Updated: 09/Jan/16 10:56
• Resolved: 13/Sep/15 16:54

Description

This JIRA is for refactoring and adding more join algorithms into a join library.

This is for joins between results from intermediate patterns, not joins that solve basic graph patterns.

Normal use is a index join algorithm but it has some requirements about variable scope. ARQ falls back to a general join mechanism if the scoping requirements aren't met (this unusual).

The general join code is not good. It should be, for example, a hash join if possible.

Relation to JENA-266: There is hash-based anti-join code in org.apache.jena.sparql.engine.index in support of MINUS. This is not a proposal to combine that code into the join library. It is not immediately clear that code to cover all cases (inner join, left join and anti-join) at once is really a good idea if it leads to excessively complicated code.

Issue Links

• relates to: JENA-885 Poor performance and timeout failure with BIND in nested OPTIONALs