How to store the time zone with a timestamp

BTW, if you wanted a more integrated solution, you could build a custom
type that would store the timestamp info. There's a good chance such
code would end up being what's used in the server as the official type,
too.

On Fri, Dec 16, 2005 at 08:57:04AM -0800, Andrew B. Young wrote:

I just realized that the type "timestamp with time zone" does NOT store
the time zone!
(And I just found this support list to look for help.)

I am developing an application that stores power (watts) readings from
meters
located around the world (abridged)--
power_meter_id integer NOT NULL,
"ts" timestamp with time zone NOT NULL,
power_reading real NOT NULL

Not storing the originating TZ is unacceptable. My search of this list
finds a number of
helpful discussions (including a reference to a TODO; soon I hope!) I
don't know
database programming and wonder if experienced users could reply with
some code
they've implemented.

I think the best solution is along Karsten's, which I believe goes like
this--
1) "ts" timestamp with time zone NOT NULL,
"tz" char( 6 ) NOT NULL, # '-12:00' to '+13:00'
2) A insert trigger that populates "tz"
3) Some function foo() that
a) calls timezone( tz, ts ) and
b) tacks on tz to the resulting string
in a "SELECT power_meter_id, foo( ts, tz ), power_reading;"

ANY snip its of code that implements anything related would be appreciated.
I can probably gin the complete solution seeing enough examples.

Thanks!
Andrew

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Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461

On Fri, Dec 16, 2005 at 03:18:04PM -0600, Jim C. Nasby wrote:

BTW, if you wanted a more integrated solution, you could build a custom
type that would store the timestamp info. There's a good chance such
code would end up being what's used in the server as the official type,
too.

Well, I wrote a module for storing arbitrary tags with base types. One
of the uses would be for a timestamp that remembers the timezone. I
havn't received all that much feedback on it which leads me to conclude
timestamps-remebering-timezones are not a heavily requested feature.
It's probably on the same level as the ENUM suggested a while ago.
Interesting, but not enough to get it included into core.

http://svana.org/kleptog/pgsql/taggedtypes.html

That said, I'd love for a variation of this to be included since I
beleive it has a lot of applications not thought of yet. If user-types
could define their own typmod values, that'd make it complete.

Have a nice day,
--
Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/

On Fri, Dec 16, 2005 at 11:25:22PM +0100, Martijn van Oosterhout wrote:

On Fri, Dec 16, 2005 at 03:18:04PM -0600, Jim C. Nasby wrote:

BTW, if you wanted a more integrated solution, you could build a custom
type that would store the timestamp info. There's a good chance such
code would end up being what's used in the server as the official type,
too.

Well, I wrote a module for storing arbitrary tags with base types. One
of the uses would be for a timestamp that remembers the timezone. I
havn't received all that much feedback on it which leads me to conclude
timestamps-remebering-timezones are not a heavily requested feature.
It's probably on the same level as the ENUM suggested a while ago.
Interesting, but not enough to get it included into core.

http://svana.org/kleptog/pgsql/taggedtypes.html

That said, I'd love for a variation of this to be included since I
beleive it has a lot of applications not thought of yet. If user-types
could define their own typmod values, that'd make it complete.

Wow, that's damn cool and useful. You should put it on pgFoundry (at
least as a project that links back to your site) so people can find it
there.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461

We have a TODO also:

o Allow TIMESTAMP WITH TIME ZONE to store the original timezone
information, either zone name or offset from UTC [timezone]

If the TIMESTAMP value is stored with a time zone name, interval
computations should adjust based on the time zone rules.

---------------------------------------------------------------------------

Jim C. Nasby wrote:

BTW, if you wanted a more integrated solution, you could build a custom
type that would store the timestamp info. There's a good chance such
code would end up being what's used in the server as the official type,
too.

On Fri, Dec 16, 2005 at 08:57:04AM -0800, Andrew B. Young wrote:

I just realized that the type "timestamp with time zone" does NOT store
the time zone!
(And I just found this support list to look for help.)

I am developing an application that stores power (watts) readings from
meters
located around the world (abridged)--
power_meter_id integer NOT NULL,
"ts" timestamp with time zone NOT NULL,
power_reading real NOT NULL

Not storing the originating TZ is unacceptable. My search of this list
finds a number of
helpful discussions (including a reference to a TODO; soon I hope!) I
don't know
database programming and wonder if experienced users could reply with
some code
they've implemented.

I think the best solution is along Karsten's, which I believe goes like
this--
1) "ts" timestamp with time zone NOT NULL,
"tz" char( 6 ) NOT NULL, # '-12:00' to '+13:00'
2) A insert trigger that populates "tz"
3) Some function foo() that
a) calls timezone( tz, ts ) and
b) tacks on tz to the resulting string
in a "SELECT power_meter_id, foo( ts, tz ), power_reading;"

ANY snip its of code that implements anything related would be appreciated.
I can probably gin the complete solution seeing enough examples.

Thanks!
Andrew

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message can get through to the mailing list cleanly

--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461

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