Re: jsonb format is pessimal for toast compression

On 09/15/2014 09:46 PM, Craig Ringer wrote:
> On 09/16/2014 07:44 AM, Peter Geoghegan wrote:
>> FWIW, I am slightly concerned about weighing use cases around very
>> large JSON documents too heavily. Having enormous jsonb documents just
>> isn't going to work out that well, but neither will equivalent designs
>> in popular document database systems for similar reasons. For example,
>> the maximum BSON document size supported by MongoDB is 16 megabytes,
>> and that seems to be something that their users don't care too much
>> about. Having 270 pairs in an object isn't unreasonable, but it isn't
>> going to be all that common either.
>
> Also, at a certain size the fact that Pg must rewrite the whole document
> for any change to it starts to introduce other practical changes.
>
> Anyway - this is looking like the change will go in, and with it a
> catversion bump. Introduction of a jsonb version/flags byte might be
> worthwhile at the same time. It seems likely that there'll be more room
> for improvement in jsonb, possibly even down to using different formats
> for different data.
>
> Is it worth paying a byte per value to save on possible upgrade pain?
>

This comment seems to have drowned in the discussion.

If there indeed has to be a catversion bump in the process of this, then 
I agree with Craig.


Jan

-- 
Jan Wieck
Senior Software Engineer
http://slony.info