Re: numbering plan nodes

On Thu, Sep 17, 2015 at 4:22 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> On Thu, Sep 17, 2015 at 2:23 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> I can't imagine I'd be doing anything that would break the simple case
>>> of "give every node a distinct ID".  If you are building in weird
>>> assumptions about traversal order, that might indeed be a problem.
>
>> Good to know, thanks.  With the design you proposal above, we can make
>> this insensitive to traversal order.  The only thing that would cause
>> trouble is if you somehow ended up with massive gaps in the numbering
>> sequence - e.g. if the final plan had 6 nodes, but the IDs were all 5
>> digit numbers, you'd waste a silly amount of memory relative to the
>> size of the plan.  But a few gaps (e.g. for removed SubqueryScan
>> nodes) won't be a problem.
>
> Hm ... if you quit worrying about the order-of-assignment, maybe you
> could prevent gaps from removed SubqueryScan nodes by not giving them
> IDs until after that decision is made?

Hmm, that might work.  I'll try it.

> Although it may not be worth
> any extra trouble.

Right.  If it doesn't turn out to be easy, I won't worry about it.

-- 
Robert Haas
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