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From "Thomas Mueller (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-34) Define query API
Date Tue, 03 Apr 2012 11:58:25 GMT

    [ https://issues.apache.org/jira/browse/OAK-34?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13245164#comment-13245164
] 

Thomas Mueller commented on OAK-34:
-----------------------------------

> Currently the query needs to be parsed twice.

A query only needs to be parsed twice if the method JCR API method Query.getBindVariableNames()
is used. I guess normally this method isn't used, as the application already knows the bind
variable names.

> The prepare() method would return a pre-parsed query

That's possible, but it would add another interface (Query) which isn't really necessary most
of the time. Also, it wouldn't be necessary to avoid parsing queries twice (if this is what
you are worried about). Instead of passing the parsed query to oak-jcr, the query engine in
oak-core could keep a query cache. That would also speed up executing repeated queries.

> clients could build queries for their own languages

Currently, the query parsers are within oak-core. If additional query parsers are required,
then I think oak-core is the place where they should be registered. I would like to avoid
exposing the abstract syntax tree to oak-jcr.

> QueryResult which has an inner interface called Row

Sounds good to me, I will change it.

> Result.getRows() should probably return an Iterable

I also thought about that, but I would like to keep it until we have a good use case for Iterable.

> Maybe Result.getRows() should allow for specifying offset and limit.

Some optimizations might require to know the offset and limit before executing the query (the
easiest optimization is using a limit of 0), therefore I would like to specify the offset
and limit right when executing the query.

                
> Define query API
> ----------------
>
>                 Key: OAK-34
>                 URL: https://issues.apache.org/jira/browse/OAK-34
>             Project: Jackrabbit Oak
>          Issue Type: New Feature
>          Components: core
>            Reporter: Michael Dürig
>              Labels: query
>
> Define a oak-core API for handling queries. How do we handle name space mappings, value
bindings, limit, offset, access rights. See OAK-28

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