> On Thu, Sep 17, 2020 at 02:47:54PM +0200, Pavel Stehule wrote: > > I have my concerns about the performance side of this implementation as > > well as how surprising this would be for users, but at the same time the > > patch already does something similar and the code change should not be > > that big, so why not - I can include this change into the next rebased > > version. But it still can cause some confusion as it's not going to work > > for negative indices, so > > > > update foo set a[-10] = 1; > > > > and > > > > select a[-10] from foo; > > > > can return different value from what was assigned. Otherwise, if we will > > try to fix a[-10] assignment in the same way, it will prepend the array > > and a[10] will not return the same value. > > What is semantic of negative index? It has clean semantic in C, but in > PLpgSQL?
It's just a common pattern for jsonb when a negative index count from the end of an array. I believe it was like that from the very earlier implementations, although can't comment on that from the semantic point of view.
