extract vs date_part

ISTM that it is mighty confusing that extract() and date_part() don't
accept the same set of "field" arguments.

-> SELECT EXTRACT(decade FROM TIMESTAMP '2001-02-16 20:38:40');
ERROR: parser: parse error at or near "decade"
=> SELECT EXTRACT("decade" FROM TIMESTAMP '2001-02-16 20:38:40');
ERROR: parser: parse error at or near """
=> SELECT date_part('decade', TIMESTAMP '2001-02-16 20:38:40');
date_part
-----------
200

This can be an easy grammar fix:

diff -c -r2.220 gram.y
*** gram.y 2001/02/09 03:26:28 2.220
--- gram.y 2001/02/16 19:42:42
***************
*** 4987,4992 ****
--- 4987,4993 ----
;

extract_arg: datetime { $$ = $1; }
+ | IDENT { $$ = $1; }
| TIMEZONE_HOUR { $$ = "tz_hour"; }
| TIMEZONE_MINUTE { $$ = "tz_minute"; }
;

(Using ColId instead of datetime + IDENT gives reduce/reduce conflicts
that I don't want to mess with now.)

The date_part implementation is prepared for unknown field selectors, so
this should be all safe. Comments?

--
Peter Eisentraut peter_e(at)gmx(dot)net http://yi.org/peter-e/