Re: TRIM_ARRAY

On Tue, 16 Feb 2021 at 12:54, Vik Fearing <vik(at)postgresfriends(dot)org> wrote:

> The SQL standard defines a function called TRIM_ARRAY that surprisingly
> has syntax that looks like a function! So I implemented it using a thin
> wrapper around our array slice syntax. It is literally just ($1)[1:$2].
>
> An interesting case that I decided to handle by explaining it in the
> docs is that this won't give you the first n elements if your lower
> bound is not 1. My justification for this is 1) non-standard lower
> bounds are so rare in the wild that 2) people using them can just not
> use this function. The alternative is to go through the unnest dance
> (or write it in C) which defeats inlining.
>

I don't recall ever seeing non-default lower bounds, so I actually think
it's OK to just rule out that scenario, but why not something like this:

($1)[:array_lower ($1, 1) + $2 - 1]

Note that I've used the 9.6 feature that allows omitting the lower bound.