Michael Bartmann wrote:
Dain,

I could help defining the grammar; unfortunately I'm
quite busy this week and on a long sought vacation
next week, so you'll have to be patient with me.
No rush; I won't be able to get to it for a while anyway.

The current grammar for JBossQL is not exactly tiny,
at least the JavaCC representation is a bit difficult
to read due to the way JavaCC grammars model nested
expressions.

But the things we will have to extend work on a higher
syntactical level mostly, as in

UPDATE SomeEntity SET SomeField=<expression>

which could use similar low level tokens as the existing
grammar when doing

SELECT ... WHERE SomeField=<expression>
Agreed

We'll also have to decide which features are to be supported;
One thing to think about is resultset postprocessing:
e.g. in the case of a container iterating over a
resultset it _could_ do some postprocessing if there is no
adequate sql equivalent of the eql query.

Example:

SELECT arcsinh(SomeField) ...

with a database not supporting that function. This smells
like "jet-engine" anyway; I would speak against such
postprocessing. One reason is my original wish
to support providing the generated sql to any SLSB,
and the session would simply pump it into a
jdbc driver without any knowledge about need for
postprocessing.

So are we speaking only of a transformation engine
mapping eql/jbossql to db specific sql, as would suffice
in the case of UPDATES, where there is no need to
postprocess anyway?
I have no plans to do any post processing. I also don't have plans for a real query engine. All I plan on writing my self is a cross compiler. If someone wants to write it, that would be cool.

That leaves the problem of function support across all databases. My current plan it to simply throw some sort of unsupported function exception when the query is compiled (deployment or at runtime for DynamicQL).

-dain



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