Re: [v9.5] Custom Plan API

On Wed, May 7, 2014 at 4:01 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> Agreed. My proposal is that if the planner allows the lookaside to an
> FDW then we pass the query for full execution on the FDW. That means
> that the scan, aggregate and join could take place via the FDW. i.e.
> "Custom Plan" == lookaside + FDW
>
> Or put another way, if we add Lookaside then we can just plug in the
> pgstrom FDW directly and we're done. And everybody else's FDW will
> work as well, so Citus etcc will not need to recode.

As Stephen notes downthread, Tom has already expressed opposition to
this idea on other threads, and I tend to agree with him, at least to
some degree. I think the drive to use foreign data wrappers for
PGStrom, CitusDB, and other things that aren't really foreign data
wrappers as originally conceived is a result of the fact that we've
got only one interface in this area that looks remotely like something
pluggable; and so everyone's trying to fit things into the constraints
of that interface whether it's actually a good fit or not.
Unfortunately, I think what CitusDB really wants is pluggable storage,
and what PGStrom really wants is custom paths, and I don't think
either of those things is the same as what FDWs provide.

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