Re: [HACKERS] Custom compression methods

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
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