Re: patch: function xmltable

Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> Something I just noticed is that transformTableExpr takes a TableExpr
> node and returns another TableExpr node.  That's unlike what we do in
> other places, where the node returned is of a different type than the
> input node.  I'm not real clear what happens if you try to re-transform
> a node that was already transformed, but it seems worth thinking about.

We're not 100% consistent on that --- there are cases such as RowExpr
and CaseExpr where the same struct type is used for pre-parse-analysis
and post-parse-analysis nodes.  I think it's okay as long as the
information content isn't markedly different, ie the transformation
just consists of transforming all the sub-nodes.

Being able to behave sanely on a re-transformation used to be an
issue, but we no longer expect transformExpr to support that.

                        regards, tom lane