st 7. 11. 2018 v 16:25 odesílatel Dmitry Dolgov <9erthali...@gmail.com> napsal:
> > On Fri, 12 Oct 2018 at 07:52, Pavel Stehule <pavel.steh...@gmail.com> > wrote: > > > >> > postgres=# insert into test(v) values( '[]'); > >> > INSERT 0 1 > >> > postgres=# update test set v[1000] = 'a'; > >> > UPDATE 1 > >> > postgres=# update test set v[1000] = 'a'; > >> > UPDATE 1 > >> > postgres=# update test set v[1000] = 'a'; > >> > UPDATE 1 > >> > postgres=# select * from test; > >> > ┌────┬─────────────────┐ > >> > │ id │ v │ > >> > ╞════╪═════════════════╡ > >> > │ │ ["a", "a", "a"] │ > >> > └────┴─────────────────┘ > >> > (1 row) > >> > > >> > It should to raise exception in this case. Current behave allows > append simply, but can be source of errors. For this case we can introduce > some special symbol - some like -0 :) > >> > >> Yeah, it may look strange, but there is a reason behind it. I tried to > keep the > >> behaviour of this feature consistent with jsonb_set function (and in > fact > >> they're sharing the same functionality). And for jsonb_set it's > documented: > >> > >> If the item (of a path, in our case an index) is out of the range > >> -array_length .. array_length -1, and create_missing is true, the > new value > >> is added at the beginning of the array if the item is negative, and > at the > >> end of the array if it is positive. > >> > >> So, the index 1000 is way above the end of the array v, and every new > item has > >> being appended at the end. > >> > >> Of course no one said that they should behave similarly, but I believe > it's > >> quite nice to have consistency here. Any other opinions? > > > > > > Aha - although I understand to your motivation, I am think so it is bad > design - and jsonb_set behave is not happy. > > > > I am think so it is wrong idea, because you lost some information - > field position - I push value on index 10, but it will be stored on second > position. > > The thing is that we don't store the field position in this sense anyway in > jsonb. For arrays there are dimentions, boundaries and null bitmaps > stored, but > for jsonb it's just an array of elements. If we want to store this data, we > either have to change the format, or fill in a jsonb with null values up > to the > required position (the first option is out of the scope of this patch, the > second doesn't sound that good). > I don't agree. If we use a same syntax for some objects types, we should to enforce some consistency. I don't think so you should to introduce nulls for JSONs. In this case, the most correct solution is raising a exception. Regards Pavel
