Re: patch: function xmltable
От | Pavel Stehule |
---|---|
Тема | Re: patch: function xmltable |
Дата | |
Msg-id | CAFj8pRCmvP_jmQv5Yqva-3Rt-9JCTFCUXh8LGWDEt7Y+EVTs7A@mail.gmail.com обсуждение исходный текст |
Ответ на | Re: patch: function xmltable (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: patch: function xmltable
|
Список | pgsql-hackers |
2016-11-21 21:16 GMT+01:00 Tom Lane <tgl@sss.pgh.pa.us>:
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.
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
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