[JENA-809] TransformExtendCombine breaks BINDs inside SERVICE

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Jena 2.12.1
• Fix Version/s: Jena 2.13.0
• Component/s: ARQ
• Assignee: Andy Seaborne
• Reporter: Eetu Mäkelä
• Created: 30/Oct/14 09:19
• Updated: 06/Jan/15 13:20
• Resolved: 02/Nov/14 16:56

Description

Optimization breaks BIND expressions in some situations since TransformExtendCombine was enabled in commit 4e5fe9a20d1531430ab96cb2ab9694aed9a9538b (culprit found using git bisect). I don't know exactly when or why this happens, but I hit upon this while using SERVICE. I've been able to create the following minimal example.

For the query:

SELECT * {
 SERVICE <> {
    BIND(1 AS ?foo)
    BIND(2 AS ?bar)
 }
}

qparse --explain for 2.12.0 returns:

(service <file:///home/jiemakel/qf>
  (extend ((?foo 1) (?bar 2))
    (table unit)))

which works fine, while for 2.12.1 it returns:

(service <file:///home/jiemakel/qf>
  (extend ((?bar 2))
    (extend ((?foo 1) (?bar 2))
      (table unit))))

which binds ?bar twice, and fails with BIND: Variable used when already in-scope: ?bar in BIND(2 AS ?bar)