I tried it once more, now. There is no change in the behavior. I use the $$-notation to avoid double "\" and double "'". Also there is no syntax error in this statement.
The constraint is a bad option because I have to log errors when I import a csv-file.
I need to verify the value of a column by a regular expression in an if-statement before insert or update. It should be a one to three digit value. I wrote a trigger and a trigger function. In the trigger function I want to use the following if-statement to verify the value:
IF new.value !~ E'^\d{1,3}$' THEN RAISE EXCEPTION '...some text...'; END IF;
It will not work! Why?
How about this:
IF new.value !~ E'^\\d{1,3}$' THEN
Or if you only want to check the 3digit value, without any trigger, IMHO this is much simpler:
alter table x add constraint check_is_3_digit check ( value ~ E'^\\d{3}$' );