[MARMOTTA-367] KiWi SPARQL: support for OPTIONAL

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.1-incubating
• Fix Version/s: 3.3.0
• Component/s: KiWi Triple Store
• Assignee: Sebastian Schaffert
• Reporter: Sebastian Schaffert
• Created: 15/Nov/13 12:29
• Updated: 16/Dec/14 10:00
• Resolved: 16/Sep/14 09:20

Description

The OPTIONAL construct is very popular among SPARQL users, but currently not directly supported by the KiWi SPARQL optimizations. We should investigate how OPTIONAL can properly be translated into a SQL LEFT OUTER JOIN to improve the performance of such queries.