From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Ildus Kurbangaliev <i.kurbangaliev@postgrespro.ru>
Cc: pgsql-hackers@postgresql.org, Ildar Musin <i.musin@postgrespro.ru>
Subject: Re: [HACKERS] Custom compression methods
Date: Sat, 25 Nov 2017 02:13:41 +0100
Message-ID: <e3378c06-d805-a3f5-6ea7-af2a2417361e@2ndquadrant.com> (raw)
In-Reply-To: <20171124123800.034c9208@wp.localdomain>
References: <20170907194236.4cefce96@wp.localdomain>
<20170912175505.4afa11fd@wp.localdomain>
<20171102152836.60c041e4@wp.localdomain>
<20171114162356.52e3d388@wp.localdomain>
<62e46a47-08a8-6e06-5e4f-6f52e0a13202@2ndquadrant.com>
<20171121174717.69ecd8f4@wp.localdomain>
<bfb3d34e-ba74-02cb-ca2a-43344866d9fd@2ndquadrant.com>
<20171123123849.5a686d7b@wp.localdomain>
<57daf28d-ed76-c364-a9ca-65d0ff71a36f@2ndquadrant.com>
<20171124123800.034c9208@wp.localdomain>
Hi,
On 11/24/2017 10:38 AM, Ildus Kurbangaliev wrote:
> ...
> That means compressed datums now in the column with storage
> specified as external. I'm not sure that's a bug or a feature.
>
Interesting. Never realized it behaves like this. Not sure if it's
intentional or not (i.e. bug vs. feature).
> Lets insert them usual way:
>
> delete from t2;
> insert into t2 select repeat(md5(i::text),300) from
> generate_series(1,100000) s(i);
> \d+
>
> List of relations
> Schema | Name | Type | Owner | Size | Description
> --------+------+-------+-------+---------+-------------
> public | t1 | table | ildus | 18 MB |
> public | t2 | table | ildus | 1011 MB |
>
> Maybe there should be more common solution like comparison of
> attribute properties?
>
Maybe, not sure what the right solution is. I just know that if we allow
inserting data into arbitrary tables without recompression, we may end
up with data that can't be decompressed.
I agree that the behavior with extended storage is somewhat similar, but
the important distinction is that while that is surprising the data is
still accessible.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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-hackers@postgresql.org
Cc: tomas.vondra@2ndquadrant.com, i.kurbangaliev@postgrespro.ru, i.musin@postgrespro.ru
Subject: Re: [HACKERS] Custom compression methods
In-Reply-To: <e3378c06-d805-a3f5-6ea7-af2a2417361e@2ndquadrant.com>
* 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