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

On Wed, Oct 25, 2017 at 11:59 PM, David Rowley
<david(dot)rowley(at)2ndquadrant(dot)com> wrote:
> As of today, because we include this needless [Merge]Append node, we
> cannot parallelise scans below the Append.

Without disputing your general notion that singe-child Append or
MergeAppend nodes are a pointless waste, how does a such a needless
node prevent parallelizing scans beneath it?

> Invent a ProxyPath concept that allows us to add Paths belonging to
> one relation to another relation. The ProxyPaths can have
> translation_vars to translate targetlists to reference the correct
> Vars. These ProxyPaths could exist up as far as createplan, where we
> could perform the translation and build the ProxyPath's subnode
> instead.

This idea sounds like it might have some legs, although I'm not sure
"proxy" is really the right terminology.

Like both you and Ashutosh, I suspect that there might be some other
applications for this.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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