Below regex works in Hive but not in Spark.
It throws an error dangling metacharacter * at index 3:
select regexp_extract('a|b||c','^(\\|*(?:(?!\\|\\|\\w(?!\\|\\|)).)*)');
I also tried escaping * with \\* but still it throws dangling metacharacter * at index 3.
You can use
regexp_replace(col, '^(.*)[|]{2}.*$', '$1')
See the regex demo.
Regex details:
^ - start of string(.*) - Capturing group 1 (this group value is referred to with $1 replacement backreference in the replacement pattern): any zero or more chars other than line break chars, as many as possible (the rest of the line)[|]{2} - double pipe (|| string).* - the rest of the line$ - end of string.