Re: jsonb format is pessimal for toast compression

On 09/12/2014 10:00 AM, Robert Haas wrote:
> On Fri, Sep 12, 2014 at 1:00 PM, Robert Haas <robertmhaas@gmail.com> wrote:
>> On Thu, Sep 11, 2014 at 9:01 PM, Josh Berkus <josh@agliodbs.com> wrote:
>>> So, I finally got time to test Tom's latest patch on this.
>>>
>>> TLDR: we want to go with Tom's latest patch and release beta3.
>>>
>>> Figures:
>>>
>>> So I tested HEAD against the latest lengths patch.  Per Arthur Silva, I
>>> checked uncompressed times for JSONB against compressed times.  This
>>> changed the picture considerably.
>>
>> Did you
> 
> Blah.
> 
> Did you test Heikki's patch from here?
> 
> http://www.postgresql.org/message-id/53EC8194.4020804@vmware.com
> 
> Tom didn't like it, but I thought it was rather clever.
> 

Yes, I posted the results for that a couple weeks ago; Tom had posted a
cleaned-up version of that patch, but materially it made no difference
in sizes or extraction times compared with Tom's lengths-only patch.
Same for Arthur's tests.

It's certainly possible that there is a test case for which Heikki's
approach is superior, but if so we haven't seen it.  And since it's
approach is also more complicated, sticking with the simpler
lengths-only approach seems like the way to go.

-- 
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com