Re: regexp_replace not respecting greediness

Simon Ellmann <simon(dot)ellmann(at)tum(dot)de> writes:
> With the following regular expression, the second .* seems to match non-greedily although (if I am correct) it should match greedily:
> postgres=# SELECT REGEXP_REPLACE('jane(dot)smith(at)example(dot)com', '(dot)*?(at)(dot)*', 'ab');

This is correct according to the rules given at

https://www.postgresql.org/docs/current/functions-matching.html#POSIX-MATCHING-RULES

specifically that "A branch — that is, an RE that has no top-level |
operator — has the same greediness as the first quantified atom in it
that has a greediness attribute." Because of that, the RE as a whole
is non-greedy and will match the shortest not longest amount of text
overall. The discussion in that manual section shows what to do
when you don't like the results.

> Other database systems (e.g., DuckDB, Umbra) match the whole input:

If your complaint is "but it's not like Perl!", I suggest using
a plperl function to do your regexp work.

regards, tom lane