REGEX for special character (Decode Unicode) - unicode

Question

I have try this code to decode, unicode all works fine if the comment start with any special character, symbol, space and etc shows error.
CREATE TEMP FUNCTION DecodeUnicode(s STRING) AS (
IF(s NOT LIKE '%\\u%', s,
(SELECT CODE_POINTS_TO_STRING(ARRAY_AGG(CAST(CONCAT('0x', x) AS INT64)))
FROM UNNEST(SPLIT(s, '\\u')) AS x
WHERE x != ''))
);
SELECT
original,
DecodeUnicode(original) AS decoded
FROM (
SELECT trim(r'$-\u6599\u91d1\u304c\u9ad8\u3059\u304e\uff01\uff01\uff01') AS original UNION ALL
SELECT trim(r'abcd')
);

Answer 1

Below is for BigQuery Standard SQL
#standardSQL
CREATE TEMP FUNCTION DecodeUnicode(s STRING) AS (
(SELECT CODE_POINTS_TO_STRING(ARRAY_AGG(CAST(CONCAT('0x', x) AS INT64)))
FROM UNNEST(SPLIT(s, '\\u')) AS x
WHERE x != ''
)
);
WITH `yourTable` AS (
SELECT r'$-\u6599\u91d1\u304c\u9ad8\u3059\u304e\uff01\uff01\uff01' AS original UNION ALL
SELECT r'abcd'
), uchars AS (
SELECT DISTINCT
c,
DecodeUnicode(c) uchar
FROM `yourTable`,
UNNEST(REGEXP_EXTRACT_ALL(original, r'(\\u[abcdef0-9]{4})')) c
)
SELECT
original,
STRING_AGG(IFNULL(uchar, x), '' ORDER BY pos) decoded
FROM (
SELECT
original,
pos,
SUBSTR(original,
SUM(CASE char WHEN '' THEN 1 ELSE 6 END)
OVER(PARTITION BY original ORDER BY pos) - CASE char WHEN '' THEN 0 ELSE 5 END,
CASE char WHEN '' THEN 1 ELSE 6 END) x,
uchar
FROM `yourTable`,
UNNEST(REGEXP_EXTRACT_ALL(original, r'(\\u[abcdef0-9]{4})|.')) char WITH OFFSET AS pos
LEFT JOIN uchars u ON u.c = char
)
GROUP BY original
-- ORDER BY original
What it does - it extracts all unicode characters and decode them and replace them in original string leaving non-unicodes stay as they are, so the output will be as below
original decoded
$-\u6599\u91d1\u304c\u9ad8\u3059\u304e\uff01\uff01\uff01 $-料金が高すぎ！！！
abcd abcd