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From "Jukka Zitting (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-28) Query implementation
Date Wed, 21 Mar 2012 15:49:38 GMT

    [ https://issues.apache.org/jira/browse/OAK-28?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13234437#comment-13234437

Jukka Zitting commented on OAK-28:

bq. I think it should take a query string ...

+1 together with the query language and a map of applicable namespace mappings

bq. ... it's a bit complicated to support as the JQOM classes are not easily extensible ...

Right. For example JQOM makes pretty hard assumptions about the structure of a query, making
features like "EXPLAIN", "DISTINCT" or "COUNT(*)" difficult to add. Other issues are that
JQOM assumes that the right-hand side of all comparisons are static values and that each function
maps to a separate interface and related factory method. Basically the API is designed in
a way that makes it very cumbersome to extend even for fairly minor things.
> Query implementation
> --------------------
>                 Key: OAK-28
>                 URL: https://issues.apache.org/jira/browse/OAK-28
>             Project: Jackrabbit Oak
>          Issue Type: New Feature
>          Components: core
>            Reporter: Thomas Mueller
>            Assignee: Thomas Mueller
>         Attachments: OakToJcrQueryTreeConverter.java
> A query engine needs to be implemented. 
> This includes a query parser in oak-core (where we don't want to use the JCR API), and
a query parser in oak-jcr (where the parsed query tree needs to implement the JCR API).
> To avoid writing two independent parsers, I suggest to change the parser to emit a non-JCR
query tree (so the parser can be used in oak-core). There needs to be a converter from the
non-JCR query tree to a JCR query tree, so the same parser can be used in oak-jcr.
> This will still require two independent query tree implementations (about 37 duplicated
classes: 37 classes for oak-core and 37 classes in oak-jcr). Plus it requires a tree converter.
> If somebody has a better idea please tell me :-)
> Prototype implementation of the query tree converter. Please note the class names are
only to for illustration, but I don't know yet a good naming convention. Ideas are welcome!

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