Re: WIP: Join push-down for foreign tables

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com>, Kohei KaiGai <kaigai(at)kaigai(dot)gr(dot)jp>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: WIP: Join push-down for foreign tables
Date: 2012-01-05 10:58:09
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On 03.12.2011 01:05, Tom Lane wrote:
> Heikki Linnakangas<heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
>> Hmm, so you're saying that the FDW function needs to be able to return
>> multiple paths for a single joinrel. Fair enough, and that's not
>> specific to remote joins. Even a single-table foreign scan could be
>> implemented differently depending on whether you prefer fast-start or
>> cheapest total.
> ... or ordered vs unordered, etc. Yeah, good point, we already got this
> wrong with the PlanForeignScan API. Good thing we didn't promise that
> would be stable.

This discussion withered down here...

I think the advice to Shigeru-san is to work on the API. We didn't reach
a consensus on what exactly it should look like, but at least you need
to be able to return multiple paths for a single joinrel, and should
look at fixing the PlanForeignScan API to allow that too.

Heikki Linnakangas

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