Re: [HACKERS] Removing [Merge]Append nodes which contain a single subpath

On Tue, Mar 13, 2018 at 8:20 PM, David Rowley
<david.rowley@2ndquadrant.com> wrote:
> On 14 March 2018 at 09:25, Robert Haas <robertmhaas@gmail.com> wrote:
>> What do you think about the idea of using a projection path as a proxy
>> path instead of inventing a new method?  It seems simple enough to do:
>>
>> new_path = (Path *) create_projection_path(root, new_rel, old_path,
>> old_path->pathtarget);
>>
>> ...when we need a proxy path.
>
> I'm very open to finding a better way to do this, but does that not
> just handle the targetlist issue? The proxy path also carries
> information which allows the translation of Vars in other places in
> the plan from the old rel into the vars of the new rel. Join
> conditions, sort clauses etc.
>
> Wouldn't a ProjectionPath just need the same additional translation
> fields that I've bolted onto AppendPath to make it work properly?

Well, I guess I'm not sure.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company