Re: patch: function xmltable

2016-11-21 21:16 GMT+01:00 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:

> Alvaro Herrera <alvherre(at)2ndquadrant(dot)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.
>

I was not sure in this case - using new node was more clear for me -
safeguard against some uninitialized or untransformed value. There in only
few bytes memory more overhead.

regards

Pavel

>
> regards, tom lane
>