Re: Bug #897: EXTRACT(EPOCH FROM column): Possible wrong output

pgsql-bugs(at)postgresql(dot)org writes:
> I'm not sure whether this is actually a bug, but here goes: If you define a column as TIMESTAMP WITHOUT TIME ZONE (or TIMESTAMP(0) WITHOUT TIME ZONE), EXTRACT(EPOCH FROM column) returns a time stamp that is exactly one hour later than the time stamp from a column which contains the same date but is defined WITH TIME ZONE. Please see the example for clarification.

When I do it, I get a value five hours earlier ;-)

I believe what is actually happening is that the
timestamp-without-time-zone value is treated as though it were GMT.
I'm not sure whether to consider that a bug or not.

In most other contexts, we interpret such values as being in local time
(the current server TimeZone) when it's necessary to make a distinction.
Consistency would suggest doing it that way here too, I think.

That would mean that extract(epoch from timestamp) would behave exactly
like extract(epoch from timestamp::timestamptz). To get at the current
behavior, you'd need to do something like extract(epoch from timestamp
at time zone 'gmt').

Is that what we want? Thomas, any opinion here?

regards, tom lane

> Operating system: Linux
> PostgreSQL version: 7.3 and 7.3.2 (compiled from source)

> Sample Code
> test=> \d datotest
> Table "public.datotest"
> Column | Type | Modifiers
> --------+--------------------------------+-----------
> dato | timestamp(0) with time zone |
> dato2 | timestamp(0) without time zone |

> test=> INSERT INTO datotest VALUES ( CURRENT_TIMESTAMP, CURRENT_TIMESTAMP );
> INSERT 16981 1
> test=> SELECT dato, dato2, EXTRACT(EPOCH FROM dato) AS timestamp1, EXTRACT(EPOCH FROM dato2) AS timestamp2 FROM datotest;
> dato | dato2 | timestamp1 | timestamp2
> ------------------------+---------------------+------------+------------
> 2003-02-15 11:03:19+01 | 2003-02-15 11:03:19 | 1045303399 | 1045306999
> (1 row)

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