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From "Thomas Mueller (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (OAK-33) Values in oak-core
Date Thu, 22 Mar 2012 16:02:22 GMT

    [ https://issues.apache.org/jira/browse/OAK-33?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13235676#comment-13235676
] 

Thomas Mueller commented on OAK-33:
-----------------------------------

About Scalar.getType(): 

We need some way to represent the type info (PropertyType.STRING,... PropertyType.DECIMAL),
even if we convert some values to String internally in oak-core. Otherwise we would lose data,
right?

For most part within oak-core, we could view the type of a scalar just as an opaque integer.
But within the query engine, the data type does need to have a meaning, as using string comparison
for numbers would be incorrect. What about using the same scalar types as we have property
types? Or is this something that is only important for the query engine?
                
> Values in oak-core
> ------------------
>
>                 Key: OAK-33
>                 URL: https://issues.apache.org/jira/browse/OAK-33
>             Project: Jackrabbit Oak
>          Issue Type: New Feature
>          Components: core
>            Reporter: Thomas Mueller
>
> There is no JCR API in oak-core, but we still need to deal with values and data types.
We have multiple options, I can think of:
> (A) String everywhere, as in oak-mk
> (B) Use javax.jcr.Value
> (C) An immutable "Value" class (but doesn't need to be called "Value")
> There are multiple problems with (A), for example compile time safety, and I fear the
code would get unnecessarily complex, not as efficient as it could get (specially when dealing
with numbers), memory usage would be higher.
> I think we said (B) isn't an option because we don't want to use the JCR API in oak-core
(see also OAK-16).
> As for (C), I have a first prototype, mainly because I needed it to be able to migrate
the query feature to oak-core. The prototype is in
>   org.apache.jackrabbit.oak.query.ValueFactory
>   org.apache.jackrabbit.oak.query.Value
>   org.apache.jackrabbit.oak.query.PropertyType
> It's very similar to javax.jcr (even the property types are the same), but the values
are immutable. They currently implement Comparable<Value>, but that's also open for
discussion. One sub-problem is binaries: should they contain a reference to the MicroKernel
instance, or some other "storage backend" (possibly a temp file backend)?
> Concrete suggestions (and patches) are welcome.

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