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From Duncan Groenewald <duncangroenew...@xtra.co.nz>
Subject Re: SQL Parser failing on NULL column contraint
Date Thu, 31 Aug 2006 06:12:59 GMT
Thanks - is there any documentation on how the parser works and 
explaining what is the sqlgrammer.jj file is and how is it used, etc.

Duncan

Bryan Pendleton wrote:
> Duncan Groenewald wrote:
>> Any chance someone can explain how I could modify the parser (or 
>> whatever) to be able to handle the NULL constraint ?
>
> Beware: I haven't tried this, but you could have a look at
> java/engine/org/apache/derby/impl/sql/compile/sqlgrammar.jj and
> experimentally try to modify it for yourself.
>
> In terms of the modifications, I think you'll want to look at the
> subroutine columnConstraint(), and observe how the explicitNotNull
> and explicitNull flags are handled.
>
> Notice that there is an explicit parser block for
>
>   <NOT> <NULL>
>
> I think you'll either want to add a second explicit parser block for
>
>   <NULL>
>
> or modify the existing one to
>
>   [<NOT>] <NULL>
>
> and either way you want to make sure that you manage the explicitNull
> and explicitNotNull flags properly, and that you call setNullability()
> on the dataTypeDescriptor to record the user's NULL / NOT NULL choice.
>
> Hope this helps,
>
> bryan
>
>
>


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