Backend code redefinitions to allow read/write

 of integer Unix system times.

contrib/unixdate/unixdate.sql

+-- unixdate
+-- Routines to convert int4 (Unix system time) to datetime
+--  and int4 (delta time) to timespan
+--
+-- Thomas Lockhart (lockhart@alumni.caltech.edu)
+-- 1997-11-25
+--
+-- This cheats and reuses existing code in the standard package.
+-- Can not include this directly because built-in functions are optimized
+--  into a cache and the duplicate function names abstime_datetime() and
+--  reltime_timespan() result in duplicate constants.
+--
+-- This works with Postgres v6.2 and higher.
+
+--
+-- Conversions from integer to datetime
+--
+
+CREATE FUNCTION abstime_datetime(int4)
+ RETURNS datetime
+ AS '-' LANGUAGE 'internal';
+
+CREATE FUNCTION datetime(int4)
+ RETURNS datetime
+ AS 'select abstime_datetime($1)' LANGUAGE 'SQL';
+
+CREATE FUNCTION reltime_timespan(int4)
+ RETURNS timespan
+ AS '-' LANGUAGE 'internal';
+
+CREATE FUNCTION timespan(int4)
+ RETURNS timespan
+ AS 'select reltime_timespan($1)' LANGUAGE 'SQL';
+
+--
+-- Conversions back to integer
+--
+
+CREATE FUNCTION datetime_abstime(datetime)
+ RETURNS int4
+ AS '-' LANGUAGE 'internal';
+
+CREATE FUNCTION utime(datetime)
+ RETURNS int4
+ AS 'select datetime_abstime($1)' LANGUAGE 'SQL';
+
+CREATE FUNCTION timespan_reltime(timespan)
+ RETURNS int4
+ AS '-' LANGUAGE 'internal';
+
+CREATE FUNCTION uspan(timespan)
+ RETURNS int4
+ AS 'select timespan_reltime($1)' LANGUAGE 'SQL';
+