Re: json(b)_array_elements use causes very large memory usage when also referencing entire json document

On 2017-10-06 20:51:45 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > Hm. Unrelated to the topic at hand, but I wonder how much it'd take to
> > make some of the hot-path jsonb functionality tolerant of unaligned
> > datums.
>
> Probably pretty hard given the list-of-pointers data structure inside.

Hm, it'd be a bunch of memcpy's added, that's true. But even just doing
something like that to a variant of findJsonbValueFromContainer() might
be quite rewarding.

I'm kinda wondering about treating short datums differently on platforms
that don't care much about alignment, like modern x86. It'd not take
many code changes to only do alignment copying of short datums on
platforms that care...

Greetings,

Andres Freund