Re: [PG19] jsonb_object_agg as a window function returns stale values

Hi Tom,

> One alternative could be to use the extra palloc/memcpy only when
> skip_nulls is true, after fixing uniqueifyJsonbObject to renumber
> the pairs.

v2 does that, with a narrower test for the copy. Removing null pairs
from the state is harmless unless unique_keys is also set, since the
dedup loop skips nulls before it looks for duplicates. So 0001 copies
the pairs only for jsonb_object_agg_unique_strict.

With your benchmark on a non-assert build, HEAD and v2 both take about
10 ms of backend CPU, and v1 takes 5.6 s :( .

> (Independently of all this, the documentation for the json-object
> aggregates is seriously awful.

0003 is a try at that. It says which value wins for a repeated key,
and that null values are dropped first but still count in the unique
check.

Thanks,
Shihao