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/**
testdb=> select * from f_eertree( 'redivider' );
current_root | string
--------------+-----------
r | redivider
e | edivide
d | divid
i | ivi
(4 rows)
testdb=> select * from f_eertree( 'hello' );
current_root | string
--------------+--------
l | ll
(1 row)
*/
CREATE OR REPLACE FUNCTION
f_eertree( s text )
RETURNS TABLE( current_root char, string text )
AS $CODE$
DECLARE
current int;
other int;
other_root char;
BEGIN
FOR current IN 1 .. length( s ) LOOP
current_root := substring( s FROM current FOR 1 );
FOR other IN current + 1 .. length( s ) LOOP
other_root := substring( s FROM other FOR 1 );
IF other_root <> current_root THEN
CONTINUE;
END IF;
string := substring( s, current, other - current + 1 );
IF string = reverse( string ) THEN
RETURN NEXT;
END IF;
END LOOP;
END LOOP;
RETURN;
END
$CODE$
LANGUAGE plpgsql;
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