[JENA-885] Poor performance and timeout failure with BIND in nested OPTIONALs

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Jena 2.11.2
• Fix Version/s: Jena 3.0.1
• Assignee: Andy Seaborne
• Reporter: Mark Buquor
• Created: 23/Feb/15 15:48
• Updated: 14/May/16 09:54
• Resolved: 09/Jan/16 16:46

Description

There appears to be a performance issue with BIND when used inside nested OPTIONALs. Affected queries fail to time out.

The following patterns appear to be affected:

OPTIONAL { ... OPTIONAL { ... BIND ( ... ) } }
OPTIONAL { ... OPTIONAL { ... } BIND ( ... ) }

The following patterns appear to be unaffected:

OPTIONAL { ... OPTIONAL { ... } } BIND ( ... )
OPTIONAL { ...  BIND ( ... ) }
OPTIONAL { ... } BIND ( ... )

So far, users have been able to work around the performance issue by rewriting their queries. However, the timeout failure is still a significant reliability issue, since affected queries consume resources and can run indefinitely. I've attached a testcase that exhibits the performance and timeout problems. Reproduced with a recent 2.13.0-SNAPSHOT build.

Execution Timeout (ms): 30000

Query: PREFIX ex: <http://example.com/> SELECT ?s ?valueA { OPTIONAL { ?s ex:propA ?a . OPTIONAL { ?a ex:label ?labelA . } } BIND ( IF ( BOUND (?labelA), ?labelA, ?a) as ?valueA) }
Execution time (ms): 586
Execution time (ms): 143

Query: PREFIX ex: <http://example.com/> SELECT ?s ?valueA { OPTIONAL { ?s ex:propA ?a . OPTIONAL { ?a ex:label ?labelA . } BIND ( IF ( BOUND (?labelA), ?labelA, ?a) as ?valueA) } }
Execution time (ms): 110922
Execution time (ms): 41004

Issue Links

• is related to: JENA-1023 Algebra execution join library