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(at)gmail(dot)com> wrote:
>> On Thu, Sep 11, 2014 at 9:01 PM, Josh Berkus <josh(at)agliodbs(dot)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