"reverse()" on strings

Hi,

CREATE TABLE file (name varchar(255));

I have a couple of milion filenames. I need to build index based on
extensions. A couple of possibilities come to mind:

CREATE INDEX extension_idx ON file (reverse(name));
-- but I didn't find a function called "reverse"

CREATE INDEX extension_idx ON file (regex_match( '.*(\.[^\.]*)$' );
-- but I didn't find a function called "regex_match" which would return
string matched in brackets ()

Any ideas ? Help ? Hints ?

Thanks in advance !

John

PS: if there is reverse on strings -- where could I find "reverse()" on
arrays ? - thx

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