Re: jsonb_array_length: ERROR: 22023: cannot get array length of a scalar

On Fri, Mar 2, 2018 at 11:58 AM, Alexander Farber <
alexander(dot)farber(at)gmail(dot)com> wrote:

> I see, thank you for your comments, David and Adrian.
>
> In the "tiles" column actually save either the JSON array of tiles - when
> the user plays them
>
> Or a string (which is jsonb too) concatenated of letters - when the user
> swaps the letters.
>
> Maybe I should rethink my table structure (I just want to "log" all plays,
> swaps, skips, resigns in the words_moves table)...
>
> Or maybe I should always check for the "action" column first (acts as
> enum) - before accessing "tiles" column....
>
>
​A table constraint like:

CASE WHEN action = 'Play'
THEN lengh < 0
WHEN action = 'Swap'
THEN ...
ELSE false
END

Is perfectly fine - though having actual non-null values take on different
meanings based upon the enum is generally not a good idea. I've been using
the above to enforce conditional not null constraints when I don't want to
implement explicit inheritance​.

David J.