[JENA-1365] QueryBuilder can build an invalid union-of-one query.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Jena 3.3.0
• Fix Version/s: Jena 3.4.0
• Component/s: QueryBuilder
• Assignee: Claude Warren
• Reporter: Claude Warren
• Created: 21/Jun/17 11:00
• Updated: 21/Jul/17 09:29
• Resolved: 24/Jun/17 21:53

Description

From email chain betwen Claude and Andy

is the union-of-one still legal during the construction of the query?

Its illegal in a query - UNION is

{..} UNION {..}

UNION

{..}

The
expected usage in the builder is:

    builder.addUnion( <select-type-statement> ).addUnion(
    <select-type-statement>)
    

Currently the code builds a union-of-one and adds the next union to it.

check to ensure that a union-of-one is not generated in the
final result.

At a minimum it an error to generate a union of one.

So either, throw an expection or generate "

{ pattern }

" (including inside {}) which is the moral equivalent.

IMO The second is nicer. Tat is what I changed the formatter to do so at least it generated something even if it is changing the query a bit (round trip checking will fail but then it fails currently as it can't be parsed at all)