Thanks for taking discussion to the email list.
For your question: "should I remove the overridden + operator and go with
the standard concatenation function?"
We have a similar requirement in a few places in our code (handling of
labels in SLD, and handling of embedded CQL expressions in external
graphics). In these cases rather than use "+" we use whitespace - resulting
in a list of expressions that can be evaluated).
I think ECQL has a method that takes a lis of expressions separated by ";"
as well.
Would you be with using white space to produce your Concatenate expression?
This would make the codebase a bit more consistent (and one less
opportunity for confusion).
--
Jody
--
Jody Garnett
On 11 December 2014 at 00:44, Sampo Savolainen <
sampo.savolai...@spatineo.com> wrote:
> Hi,
>
> Jody and I have been discussing my pull request on cascaded stored
> requests and we'd like to open another point to wider debate.
>
> This is regarding Jody's notes on this test case:
> https://github.com/geoserver/geoserver/pull/841#discussion-diff-21495146
>
> Some background: my implementation of cascaded stored query passes stored
> query parameters to the backend via two mechanisms:
>
> 1. The original request to the feature type backed by a cascaded
> stored query may include view parameters, just like with Virtual Table
> backed feature types.
> 2. Feature type configuration may specify mappings to the parameters.
>
> There are a two types of mappings possible in the implementation. You can
> either specify a default value (two flavours: one you can override with a
> view parameter and another you can't), or the parameter value can be
> evaluated from an expression. The discussion here is regarding these
> expressions.
>
> The expressions are written in CQL and are executed within a context where
> the query filter, basic feature type information and the query bounds are
> accessible. A stored query that my work specifically targets has a bounding
> box parameter that needs to be derived from this context. I used
> expressions instead of a hard-coded bounding box type parameter mapping to
> make the implementation more general.
>
> When I wrote the CQL expression parts, I was only aware of a single
> concatenation function in CQL, strConCat. This function only takes two
> parameters and both must be strings. So as you can see in the test
> referenced by the diff, the expression to build a bounding box becomes
> quite a mess. To avoid this, I overrode the + operator for these
> expressions so it does string concatenation if either the left hand side or
> right hand side values were strings.
>
>
> https://github.com/geotools/geotools/blob/master/modules/unsupported/wfs-ng/src/main/java/org/geotools/data/wfs/internal/v2_0/storedquery/ParameterCQLExpressionFilterFactoryImpl.java#L104
>
> However, Jody led me on to the fact that there is a multi-parameter
> concatenation function in CQL.
>
> Now the question is: should I remove the overridden + operator and go with
> the standard concatenation function?
>
>
> Also: I was unable to find reference documentation on this concatenation
> function. Maybe someone knows where it is so I can check it? Especially
> whether it allows combining numbers and strings is of interest.
>
>
> Sampo
>
>
>
> --
> Sampo Savolainen
> R&D Director, Spatineo Oy
> sampo.savolai...@spatineo.com
> +358-407555649
> Linnankoskenkatu 16 A 17, 00250 Helsinki, Finland
> www.spatineo.com, twitter.com/#!/spatineo
> www.linkedin.com/company/spatineo-inc
>
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