Re: Making jsonb_agg() faster

I realized that my patch-of-record in this thread is out of date
in the wake of 2a600a93c, because it had some code catering to the
possibility that timestamp[tz] is pass-by-reference. While it
still compiled and worked, we don't want to commit it like that.

v2-0001 takes care of that, and also adopts your suggestion in [1]
about not using two calls of pushJsonbValueScalar where one would do.
I also did a bit more micro-optimization in appendKey, appendValue,
appendElement to avoid redundant copying, because perf testing showed
that appendElement is still a hot-spot for jsonb_agg. Patches 0002
and 0003 are unchanged.

I did not adopt your changes in [2], because they didn't really
seem like improvements to me.

regards, tom lane

[1] https://www.postgresql.org/message-id/CACJufxGFzbRDnyG-%3DWZ3RgkVUwOZexUobGDrA3n5bj8MxrAZvQ%40mail.gmail.com
[2] https://www.postgresql.org/message-id/CACJufxGHLYtvOAB7uA59C9Lz%2BrDPta5Egiii-B5opsZbw6eDDQ%40mail.gmail.com