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

["David G. Johnston" <david.g.johnston@xxxxxxxxx>]

On Fri, Mar 2, 2018 at 11:58 AM, Alexander Farber <alexander.farber@xxxxxxxxx> 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 = "">

           THEN lengh < 0

           WHEN action = "">

           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.