my_Query –

SELECT (regexp_matches('datavalue=Document{{value=[5]}}', 'datavalue=Document{{value=([^d}},'']+)'))[1] response;

current output is square bracket – [5]

I require without square bracket – 5

>Solution :

To extract a part of a string based on a regex, substring() is the better alternative:

substring('datavalue=Document{{value=[5]}}' from 'datavalue=Document{{value=\[([0-9]+)\]}}') response;