jsonb_array_length: ERROR: 22023: cannot get array length of a scalar - Mailing list pgsql-general

Good afternoon,

in PostgreSQL 10.3 I have the following table with a jsonb column:

#  \d words_moves;
                                     Table "public.words_moves"
 Column |           Type           | Collation | Nullable |                 Default
--------+--------------------------+-----------+----------+------------------------------------------
 mid    | bigint                   |           | not null | nextval('words_moves_mid_seq'::regclass)
 action | text                     |           | not null |
 gid    | integer                  |           | not null |
 uid    | integer                  |           | not null |
 played | timestamp with time zone |           | not null |
 tiles  | jsonb                    |           |          |
 score  | integer                  |           |          |
Indexes:
    "words_moves_pkey" PRIMARY KEY, btree (mid)
Check constraints:
    "words_moves_score_check" CHECK (score >= 0)
Foreign-key constraints:
    "words_moves_gid_fkey" FOREIGN KEY (gid) REFERENCES words_games(gid) ON DELETE CASCADE
    "words_moves_uid_fkey" FOREIGN KEY (uid) REFERENCES words_users(uid) ON DELETE CASCADE
Referenced by:
    TABLE "words_daily" CONSTRAINT "words_daily_mid_fkey" FOREIGN KEY (mid) REFERENCES words_moves(mid) ON DELETE CASCADE
    TABLE "words_scores" CONSTRAINT "words_scores_mid_fkey" FOREIGN KEY (mid) REFERENCES words_moves(mid) ON DELETE CASCADE

Here are some records (please pardon the non-english chars):

# 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

I would like to get the length of the tiles array (because in my word game 7 played tiles mean +15 score bonus) - but that call fails for some reason:

#  select mid, 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

What am I doing wrong here please?

Regards
Alex