pg.ddx.io  pgsql-general@postgresql.org mailing list archive  

help / color / mirror / Atom feed
From: Andrew Dunstan <andrew@dunslane.net>
To: Zheng Yang <zhengyang4k@gmail.com>
Cc: Shiv <rama.theone@gmail.com>
Cc: Selena Deckelmann <selena@chesnok.com>
Cc: Alvaro Herrera <alvherre@commandprompt.com>
Cc: Guillaume Lelarge <guillaume@lelarge.info>
Cc: pgsql-students <pgsql-students@postgresql.org>
Subject: Re: foreign data wrappers
Date: Sat, 26 Mar 2011 11:07:17 -0400
Message-ID: <4D8E0125.9060905@dunslane.net> (raw)
In-Reply-To: <603812A0-F464-44AE-8A90-DF9BD1DC2DB9@gmail.com>
References: <AANLkTi=FhaO5mX_YdqqsF1Yh0YNEHW8H1f0AUdpE0Fmo@mail.gmail.com>
	<690867AB-C50B-4354-91D0-8A0811639C4C@gmail.com>
	<AANLkTimKc4Jb4ydk=GO3shdv0gTPyad+y9z_kXXVKZoq@mail.gmail.com>
	<4D879CD0.5030803@dunslane.net>
	<AANLkTi=0KD_ef9XDJde52nb0n5YgysMHTjWwkKZurDR-@mail.gmail.com>
	<3EF9E4CC-CF42-4B45-86FF-4CB9D46D7442@gmail.com>
	<4D8AF8C2.3000007@lelarge.info>
	<4ACC318A-1B6F-49A5-9B02-49EEAF7B97C7@gmail.com>
	<1300985156-sup-3058@alvh.no-ip.org>
	<47676.208.91.122.102.1300985713.squirrel@dunslane.net>
	<AANLkTinCjkp2rxwivGVXZj5=bYpa4Bx=X0w6BWR=Vm0Q@mail.gmail.com>
	<AANLkTi=NuFBQBhtEBuaPR9ZzhnqPCaVtpsuJ-eZ21GpF@mail.gmail.com>
	<603812A0-F464-44AE-8A90-DF9BD1DC2DB9@gmail.com>



On 03/24/2011 10:07 PM, Zheng Yang wrote:
>
>
> I've briefly gone through the slides. Regarding the 6 callbacks, is 
> that correct to say that a full table scan will always be performed 
> irregardless of the sql statement,
> the FDW is blind to the sql query performed, right?

Yes, fairly much. If the feed is large you need some way to pass a limit 
to the foreign side, possibly via table options. I'm fairly sure you 
won't be able to get it via the SELECT statement.

>
> And can anyone help explain what a planner is? What does this "provide 
> cost estimates to planner" mean? Thanks!


See <http://www.postgresql.org/docs/current/static/planner-optimizer.html;

If you're going to work on PostgreSQL code you need to read the docs.

cheers

andrew




view thread (37+ messages)  latest in thread

Message-ID: <4D8E0125.9060905@dunslane.net>
Permalink:  ../4D8E0125.9060905@dunslane.net/
Also on:    postgresql.org/message-id/4D8E0125.9060905@dunslane.net

 · 

reply
Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: pgsql-general@postgresql.org
  Cc: andrew@dunslane.net, zhengyang4k@gmail.com, rama.theone@gmail.com, selena@chesnok.com, alvherre@commandprompt.com, guillaume@lelarge.info, pgsql-students@postgresql.org
  Subject: Re: foreign data wrappers
  In-Reply-To: <4D8E0125.9060905@dunslane.net>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox