Re: Why is writing JSONB faster than just JSON?

Dmitry Dolgov <9erthalion6(at)gmail(dot)com> writes:
> On Wed, Apr 14, 2021 at 10:26:23AM -0400, Tom Lane wrote:
>> My own guess about this, without having tried to reproduce it, is that
>> JSONB might end up physically smaller than JSON, resulting in less work
>> to push the toasted datum out to disk. This'd depend a lot on your
>> formatting habits for JSON, of course. But in any case, it'd be worth
>> comparing pg_column_size() results to see what's up with that.

> Oh, of course I've missed that the input I was using was indeed
> formatted, without formatting both cases perform equally well and I
> can't reproduce the issue. Although if I understand correctly the
> original code in question doesn't actually do any formatting.

My point was that for JSON, after validating that the input is
syntactically correct, we just store it as-received. So in particular
the amount of whitespace in the value would depend on how the client
had chosen to format the JSON. This'd affect the stored size of
course, and I think it would have an effect on compression time too.

regards, tom lane