> Per discussion here: > > https://www.postgresql.org/message-id/163636931138.8076.5140809232053731248%40wrigleys.postgresql.org > > We can now easily document the array_length behavior of returning null instead of zero for an empty array/dimension. > > I added an example to the json_array_length function to demonstrate that it does return 0 as one would expect, but contrary to the SQL array behavior. > > I did not bother to add examples to the other half dozen or so "_length" functions that all produce 0 as expected. Just the surprising case and the adjacent one.
One tiny nitpick I have is that this example will not work if used literally, as is:
``` =# select array_length(array[], 1); ERROR: cannot determine type of empty array LINE 1: select array_length(array[], 1); ```
Maybe it's worth using `array_length(array[] :: int[], 1)` instead.
I think subconsciously the cast looked ugly to me so I probably skipped adding it. I do agree the example should be executable though, and most of the existing examples use integer[] (not the abbreviated form, int) so I'll plan to go with that.
