David Kennedy wrote:
It appears that xpath union queries are not supported, but it also appears
as though this cannot be accomplished by SQL either. I get exceptions
stating an invalid path clause. My queries look like this:
(s1) statement = "/jcr:root/a/b/c/d union /jcr:root/a/e/f"
s1 will execute without exception, however will return 0 hits, but the
nodes exist in the repository. Is xpath union supported with the
jackrabbit implementation?
no, jackrabbit currently does not support the union operator. but this
is certainly an enhancement that we will implement in the near future.
See also the following thread:
http://thread.gmane.org/gmane.comp.apache.jackrabbit.devel/6476
(s2) statement = "SELECT * FROM nt:base WHERE jcr:path =
'/jcr:root/a/b/c/d' OR jcr:path = '/jcr:root/a/e/f'"
s2 will fail with javax.jcr.query.InvalidQueryException: Invalid
combination of jcr:path clauses which results from an
IllegalArgumentException because there is no merging path (%). Why is a
merging path necessary if I am using '='?
the sql query parser basically tries to create a xpath equivalent query
from the sql statement. that's why it tries to merge multiple jcr:path
clauses into a unified one.
in the end jackrabbit only implements one abstract query tree which is
more or less syntax independent. though it is very similar to XPath. See
also:
http://jackrabbit.apache.org/doc/arch/operate/query.html
(s3) statement = "SELECT * FROM nt:base WHERE jcr:path LIKE
'/jcr:root/a/b/c/d' OR jcr:path LIKE '/jcr:root/a/e/f'"
s2 will fail with javax.jcr.query.InvalidQueryException: Invalid
combination of jcr:path clauses which results from an
IllegalArgumentException because there is no merging path (%).
(s4) statement = "SELECT * FROM nt:base WHERE jcr:path =
'/jcr:root/a/b/c/d' OR jcr:path LIKE '/jcr:root/a/e/f/%'"
s2 will fail with javax.jcr.query.InvalidQueryException: Invalid
combination of jcr:path clauses which results from an
NoSuchElementException because the two specified paths are not sharing the
same path. Similar failure if I use LIKE for both and wildcard both paths
(/%).
the reason why s3 and s4 fail are the same as above.
Why don't any of these work? Is xpath union expected to be supported?
not yet, but I hope we can implement it in the near future.
regards
marcel
