Re: Horizontal scalability/sharding

From: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>
To: Bruce Momjian <bruce(at)momjian(dot)us>, Josh Berkus <josh(at)agliodbs(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Mason S <masonlists(at)gmail(dot)com>, Oleg Bartunov <obartunov(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Horizontal scalability/sharding
Date: 2015-09-01 03:30:35
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On 2015/09/01 9:54, Bruce Momjian wrote:
> On Mon, Aug 31, 2015 at 05:10:11PM -0700, Josh Berkus wrote:
>>> As far as (3) is concerned, why
>>> wouldn't we use the foreign data wrapper interface, and specifically
>>> postgres_fdw? That interface was designed for the explicit purpose of
>>> allowing access to remote data sources, and a lot of work has been put
>>> into it, so it would be highly surprising if we decided to throw that
>>> away and develop something completely new from the ground up.
>> Well, query hooks are also a capability which we already have, and is
>> mature. Citus has already posted about why they chose to use them instead.
>> As long as you recognize that the FDW API (not just the existing fdws)
>> will need to expand to make this work, it's a viable path.
> Uh, we already have a list of things we need to add to FDWs to make them
> work, and Citus Data has provided a document of more things that are
> needed,

My top priority is postgres_fdw join pushdown, but I also plan to work
on update pushdown [1] for 9.6, which couldn't make it into 9.5. I
think that would resolve the following issue mentioned in the document:

UPDATE and DELETE operations are performed by first fetching
records from the table scanning functions, and then going over
the fetched records. If the user wanted to update a single row,
this involved first pulling rows and then updating related

Best regards,
Etsuro Fujita


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