How to extract miliseconds from timestamp dynamically in postgres plpgsql? - postgresql

Question

I want to get milliseconds from a 'Timestamp with timezone' using a plsql function.
I am able to generate the following function, but it is leading to truncation of miliseconds.
CREATE or REPLACE FUNCTION getMSFromTime(t1 timestamp with time zone)
RETURNS bigint AS $$
declare time1 double precision ;
BEGIN
SELECT EXTRACT(EPOCH FROM t1) into time1;
return time1;
END;
$$ LANGUAGE plpgsql;
but it ignores miliseconds
SELECT getMSFromTime('2019-02-11 08:01:33.423+00') //1549872093
SELECT getMSFromTime('2019-02-11 08:01:33.000+00') //1549872093
I am able to get a PostgreSQL way so that millisecond decimals are preserved as well, using:
SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE '2019-02-11 08:01:33.423+00'); // 1549872093.423
But I am not able to integrate it into a function and it gives following error:
syntax error at or near "t1"
LINE 5: ...ELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE t1) into t..
CREATE or REPLACE FUNCTION getMSFromTime2(t1 timestamp with time zone)
RETURNS bigint AS $$
declare time1 double precision ;
BEGIN
SELECT EXTRACT(EPOCH FROM TIMESTAMP WITH TIME ZONE t1) into time1;
return time1;
END;
$$ LANGUAGE plpgsql;
Please suggest a way so as to create a PostgreSQL function which can do this functionality.

Answer 1

extract() returns a double value that represents seconds, by casting that to a bigint you lose the fractional seconds (=milliseconds)
If you want a bigint representing milliseconds, you need to multiple the result with 1000.
There is also no reason to use PL/pgSQL for such a simple thing:
CREATE or REPLACE FUNCTION getmsfromtime(t1 timestamp with time zone)
RETURNS bigint
AS $$
SELECT (EXTRACT(EPOCH FROM t1)*1000)::bigint;
$$
LANGUAGE sql;