[jira] [Created] (OAK-4265) XPath: support limited form of "union"

["Thomas Mueller (JIRA)" <ji...@apache.org>]

Thomas Mueller created OAK-4265:
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             Summary: XPath: support limited form of "union"
                 Key: OAK-4265
                 URL: https://issues.apache.org/jira/browse/OAK-4265
             Project: Jackrabbit Oak
          Issue Type: New Feature
          Components: query
            Reporter: Thomas Mueller
            Assignee: Thomas Mueller
             Fix For: 1.6


Currently, SQL-2 supports multiple paths restrictions combined with "or", and it supports "union". XPath doesn't support either. It would be good if this is supported, specially the "multiple paths" part.

I think it makes sense to convert this to a SQL-2 "union" in all cases, even if it's just multiple paths.

It doesn't need to be a "generic" solution, so that "|" doesn't need to be supported at every place (for example in the condition, or in the "order by"). But it would be nice if multiple independent queries, with one order by, could be supported.

Implementation note: what makes this a bit complicated is support for "order by".

For example:

{noformat}
/jcr:root/(content|lib)/element(*, nt:base) order by @title

select [jcr:path], [jcr:score], * 
from [nt:base] as a 
where ischildnode(a, '/content') 
/* xpath: /jcr:root/content/element(*, nt:base) order by @title */ 
union select [jcr:path], [jcr:score], * 
from [nt:base] as a 
where ischildnode(a, '/lib') 
/* xpath: /jcr:root/lib/element(*, nt:base) order by @title */ 
order by [title]
{noformat}



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