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

On 03/02/2018 10:43 AM, Alexander Farber wrote:
> # select * from words_moves where gid=609 limit 3;
> -[ RECORD 1
> ]----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> mid    | 1040
> action | play
> gid    | 609
> uid    | 1192
> played | 2018-03-02 10:13:57.943876+01
> tiles  | [{"col": 3, "row": 7, "value": 2, "letter": "С"}, {"col": 4,
> "row": 7, "value": 1, "letter": "О"}, {"col": 5, "row": 7, "value": 2,
> "letter": "П"}, {"col": 6, "row": 7, "value": 0, "letter": "Л"}, {"col":
> 7, "row": 7, "value": 3, "letter": "Я"}]
> score  | 10
> -[ RECORD 2
> ]----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> mid    | 1041
> action | play
> gid    | 609
> uid    | 7
> played | 2018-03-02 10:56:58.72503+01
> tiles  | [{"col": 3, "row": 8, "value": 2, "letter": "В"}, {"col": 3,
> "row": 9, "value": 1, "letter": "И"}, {"col": 3, "row": 10, "value": 2,
> "letter": "Т"}, {"col": 3, "row": 11, "value": 2, "letter": "К"},
> {"col": 3, "row": 12, "value": 1, "letter": "А"}]
> score  | 14
> -[ RECORD 3
> ]----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> mid    | 1043
> action | play
> gid    | 609
> uid    | 1192
> played | 2018-03-02 11:03:58.614094+01
> tiles  | [{"col": 0, "row": 10, "value": 2, "letter": "С"}, {"col": 1,
> "row": 10, "value": 2, "letter": "М"}, {"col": 2, "row": 10, "value": 1,
> "letter": "О"}, {"col": 4, "row": 10, "value": 2, "letter": "Р"}]
> score  | 13
>
> #  select column_name, data_type from information_schema.columns where
> table_name='words_moves';
>  column_name |        data_type
> -------------+--------------------------
>  mid         | bigint
>  action      | text
>  gid         | integer
>  uid         | integer
>  played      | timestamp with time zone
>  tiles       | jsonb
>  score       | integer
> (7 rows)
>
> #  select jsonb_array_length(tiles) from words_moves where gid=609 limit 3;
>  jsonb_array_length
> --------------------
>                   5
>                   5
>                   4
> (3 rows)
>
> BUT:
>
> #  select jsonb_array_length(tiles) from words_moves where gid=609 ;
> ERROR:  22023: cannot get array length of a scalar
> LOCATION:  jsonb_array_length, jsonfuncs.c:1579
>
>
> Which means only some data is bad, but how to find it please?

What is? :

select count(*) from words_moves where gid=609;

A simplistic approach would be:

select mid, jsonb_array_length(tiles) from words_moves where gid=609
order by mid limit x;

where you increment x until you trigger the error.

A more sophisticated approach would be to use plpgsql EXCEPTION handling:

https://www.postgresql.org/docs/10/static/plpgsql-control-structures.html#PLPGSQL-ERROR-TRAPPING

and create a function that loops through:

select jsonb_array_length(tiles) from words_moves where gid=609 ;

and RAISES a NOTICE for each incorrect value along with its mid value.

>
>
>

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com