Date: Mon, 27 Feb 2017 13:54:24 -0500
From: Bruce Momjian <bruce@momjian.us>
To: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Partitioned tables and relfilenode
Message-ID: <20170227185424.GA421@momjian.us>
References: <2b0d42f2-3a53-763b-c9c2-47139e4b1c2e@lab.ntt.co.jp>
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On Fri, Feb 10, 2017 at 03:19:47PM +0900, Amit Langote wrote:
> The new partitioned tables do not contain any data by themselves.  Any
> data inserted into a partitioned table is routed to and stored in one of
> its partitions.  In fact, it is impossible to insert *any* data before a
> partition (to be precise, a leaf partition) is created.  It seems wasteful
> then to allocate physical storage (files) for partitioned tables.  If we
> do not allocate the storage, then we must make sure that the right thing
> happens when a command that is intended to manipulate a table's storage
> encounters a partitioned table, the "right thing" here being that the
> command's code either throws an error or warning (in some cases) if the
> specified table is a partitioned table or ignores any partitioned tables
> when it reads the list of relations to process from pg_class.  Commands
> that need to be taught about this are vacuum, analyze, truncate, and alter
> table.  Specifically:
> 
> - In case of vacuum, specifying a partitioned table causes a warning
> 
> - In case of analyze, we do not throw an error or warning but simply
>   avoid calling do_analyze_rel() *non-recursively*.  Further in
>   acquire_inherited_sample_rows(), any partitioned tables in the list
>   returned by find_all_inheritors() are skipped.
> 
> - In case of truncate, only the part which manipulates table's physical
>   storage is skipped for partitioned tables.
> 
> - ATRewriteTables() skips on the AlteredTableInfo entries for partitioned
>   tables, because there is nothing to be done.
> 
> - Since we cannot create indexes on partitioned tables anyway, there is
>   no need to handle cluster and reindex (they throw a meaningful error
>   already due to the lack of indexes.)

I don't think we are doing this, but if the parent table doesn't have a
physical file pg_upgrade will need to be taught that.  We have that case
now for unlogged tables on standby servers that we need to address.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
+                      Ancient Roman grave inscription +


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