rvesse commented on code in PR #1620:
URL: https://github.com/apache/jena/pull/1620#discussion_r1025030591
##########
jena-arq/src/main/java/org/apache/jena/sparql/algebra/optimize/TransformPathFlatternStd.java:
##########
@@ -35,8 +35,15 @@
/** The path transformation step exactly as per the SPARQL 1.1 spec.
* i.e. joins triples rather creating BGPs.
+ * <p>
* It does not produce very nice execution structures so ARQ uses
- * a functional equivalent, but different, transformation.
+ * a functional equivalent, but different, transformation, see {@link
TransformPathFlattern}
+ * </p>
+ * <p>
+ * However for users who are using property paths in their queries heavily
there may be benefits to using this
+ * transform over the simpler one. The {@link
org.apache.jena.query.ARQ#optPathFlattenExtended} symbol can be set in
+ * an ARQ context to enable this transform in preference to the simpler
transform.
+ * </p>
Review Comment:
Interestingly the `:p{2}` case actually looks to be expanded the wrong way
round (at least to my eye) in the current code. It produces the following:
```
(prefix ((: <http://example/>))
(sequence
(path ??P0 (pathN* :p) :T1)
(bgp
(triple ?x :p ??P1)
(triple ??P1 :p ??P0)
)))
```
When I'd expect to see the `bgp` first followed by the `path` operator
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