Subject: Re: Declarative partitioning
To: pgsql-hackers@postgresql.org
References: <55D3093C.5010800@lab.ntt.co.jp>
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Message-ID: <56A23484.4000504@2ndquadrant.com>
Date: Fri, 22 Jan 2016 14:54:12 +0100
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Hi Amit,

thanks for working on this. Seems the last version of the patch was 
submitted more than 2 months ago and I believe large parts of it will 
get reworked based on the extensive discussion on this list, so I 
haven't looked at the code at all.

I'd like to comment on the one thing and that's the syntax. It seems to 
me we're really trying to reinvent the wheel and come up with our own 
version of the syntax. Is there a particular reason why not to look at 
the syntax of the other databases and adapt as much of the existing 
syntax as possible?

I think that's for a few reasons - firstly it makes the life much easier 
for the DBAs and users who are either migrating to PostgreSQL or have to 
manage a mix of databases. Secondly, it serves as a valuable source of 
engineering info, preventing the "I haven't thought of this use case" 
problem.

An example of this is the proposed syntax for adding a partition

   CREATE TABLE measurement_fail
   PARTITION OF measurement
   FOR VALUES START ('2006-02-15') END ('2006-03-01');

which seems a bit awkward as both the databases I'm familiar with 
(Oracle and Sybase) use ALTER TABLE to do this

   ALTER TABLE measurement
     ADD PARTITION measurement_fail VALUES LESS THAN ( ... )

And so on for the other commands.

That being said, I entirely agree with Simon (and others) that getting 
the planner part work is the crucial part of the patch. But I also think 
that a proper abstraction (thanks to good syntax) may be a valuable hint 
how to define the catalogs and such.

regards

--
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services


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