I was looking at a couple of queries and found that
SELECT * WHERE {
?x a <foo> .
OPTIONAL{ ?x <bar> ?bar } .
OPTIONAL{ ?y <baz> ?baz }
}
becomes
(leftjoin
(leftjoin
(bgp (triple ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<file:///home/claude/workspace/RoadMap/foo>))
(bgp (triple ?x <file:///home/claude/workspace/RoadMap/bar> ?bar)))
(bgp (triple ?x <file:///home/claude/workspace/RoadMap/baz> ?baz)))
BUT ....
SELECT * WHERE {
?x a <foo> .
OPTIONAL{ ?x <bar> ?bar .
?y <baz> ?baz }
}
becomes
leftjoin
(bgp (triple ?x <http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<file:///home/claude/workspace/RoadMap/foo>))
(bgp
(triple ?x <file:///home/claude/workspace/RoadMap/bar> ?bar)
(triple ?x <file:///home/claude/workspace/RoadMap/baz> ?baz)
))
It seems to me that the 2nd form is much more efficient. (Am I wrong here?)
That leads me to ask "Is there ever a time when 2 adjacent option
statements can not be merged into a single statement?"
And if not, should the parser be optimized to do the merging?
Claude
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