德鲁伊 SQL：得到 substring 问题

Question

There is the table column which holds the comma-separated values, eg:

abc321,rd512,spwewr

I need to extract the substring which starts from the user-defined pattern. Example:

Input Pattern |  Expected result
abc              abc321
r                rd512
spwe             spwewr
b                NULL

Following fails in Druid SQL:

SELECT SUBSTRING('abc321,rd512,spwewr', POSITION('r' IN 'abc321,rd512,spwewr'), 2)

This is the known Druid bug: " Substring operator converter does not handle non-constant literals correctly":

https://issues.apache.org/jira/browse/CALCITE-2226

I think the way to go is to use REGEXP_EXTRACT() or REGEXP_LIKE() but I cannot figure out the specific syntax.

Answer 1

select regexp_extract('abc321,rd512,spwewr', 'rd[^,]+', 0)