Re: jsonb format is pessimal for toast compression

On Mon, Sep 15, 2014 at 3:09 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> On 09/15/2014 10:23 AM, Claudio Freire wrote:
>> Now, large small keys could be 200 or 2000, or even 20k. I'd guess
>> several should be tested to find the shape of the curve.
>
> Well, we know that it's not noticeable with 200, and that it is
> noticeable with 100K. It's only worth testing further if we think that
> having more than 200 top-level keys in one JSONB value is going to be a
> use case for more than 0.1% of our users. I personally do not.

FWIW, I have written one (1) application that uses JSONB and it has
one sub-object (not the top-level object) that in the most typical
configuration contains precisely 270 keys. Now, granted, that is not
the top-level object, if that distinction is actually relevant here,
but color me just a bit skeptical of this claim anyway. This was just
a casual thing I did for my own use, not anything industrial strength,
so it's hard to believe I'm stressing the system more than 99.9% of
users will.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company