Re: [DOCS] Re: FE/BE protocol revision patch

>
> > > 1. Implement addition of atttypmod field to RowDescriptor messages.
> > > The client-side code is there but ifdef'd out. I have no idea
> > > what to change on the backend side. The field should be sent
> > > only if protocol >= 2.0, of course.
>
> Hmm. I was hoping to do something in the backend to allow data types
> like numeric(p,s) which take multiple qualifying arguments (in this
> case, precision and scale). One possibility was to shoehorn both fields
> into the existing atttypmod 16-bit field.
>
> Seems like atttypmod is now being used for things outside of the
> backend, but I'm not sure how to support these other uses with these
> other possible data types.

We are just passing it back. There is no special handling of atttypmod
that you need to worry about. I think we pass it back to Openlink can
know the actual length of the char() and varchar() fields without doing
a dummy select. However, they better know it is a char()/varchar()
field before using it for such a purpose, because it could be used from
something else later on, as you suggest.

> A better general approach to the type qualifier problem might be to
> define a variable-length data type which specifies column
> characteristics, and then pass that around. For character strings, it
> would have one field, and for numeric() and decimal() it would have two.

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