I think you are looking for HaskellDB,

thanks, I'll look into it.

As with LINQ you need to put an initial effort into describing the tables [...]

according to the documentation, that's what dbdirect is for? I see the source, but not how to build it. J.

Johannes Waldmann writes:

ok, so I guess I need haskelldb-hdbc-postgresql but hdbc-postgresql has build failures http://hackage.haskell.org/package/HDBC-postgresql

Looks like HDBC-postgresql's Setup.hs needs to be updated to use newer versions of Cabal properly; if you're using the latest release of the Haskell Platform then I think it will build OK. -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com

anyone know what's happening here? I get this when executing a query via haskelldb-hdbc-postgresql-0.12 (The date is actually in the DB, so it's not a connection problem.) Convertible: error converting source data SqlString "2008-10-29 00:00:00" of type SqlValue to type Data.Time.LocalTime.LocalTime.LocalTime: Cannot parse using default format string "%Y-%m-%dT%T%Q"

On Thu, Feb 4, 2010 at 7:38 PM, Colin Paul Adams wrote:

...

...

...

...

...

"Johannes" == Johannes Waldmann writes:

Johannes> anyone know what's happening here? I get this when Johannes> executing a query via haskelldb-hdbc-postgresql-0.12 (The Johannes> date is actually in the DB, so it's not a connection Johannes> problem.)

Johannes> Convertible: error converting source data SqlString Johannes> "2008-10-29 00:00:00" of type SqlValue to type Johannes> Data.Time.LocalTime.LocalTime.LocalTime: Cannot parse Johannes> using default format string "%Y-%m-%dT%T%Q"

I had this sort of problem. I sent a patch on the haskell-db list to use UTC - I believe the release behaviour is incorrect.

You might check the list archives, as they have a better memory than I.

I actually just came up against this as well in HDBC-postgresql. As a workaround, when I read a timestamp I concatenate with an empty string (||'') and then read with my own parse string:

"%Y-%m-%d %T%Q" This seems to work just fine. I'd like to debug it more, but I'm working on a short-deadline project. Hopefully when the month is out I'll be able to submit some patches for the problems I've run into. The other one that comes to mind off hand is I can't write to BYTEA fields either. Michael

On 05/02/10 07:04, Johannes Waldmann wrote:

...

Johannes> Data.Time.LocalTime.LocalTime.LocalTime: Cannot parse Johannes> using default format string "%Y-%m-%dT%T%Q"

this actually comes from the default format string that is defined in old-locale:System.Locale?

iso8601DateFormat :: Maybe String -> String iso8601DateFormat mTimeFmt = "%Y-%m-%d" ++ case mTimeFmt of Nothing -> "" Just fmt -> 'T' : fmt

and this can't be right - the 'T' is invalid?

It's very much valid, see http://en.wikipedia.org/wiki/ISO_8601 /M -- Magnus Therning (OpenPGP: 0xAB4DFBA4) magnus＠therning．org Jabber: magnus＠therning．org http://therning.org/magnus identi.ca|twitter: magthe

On Fri, Feb 5, 2010 at 10:55 AM, Johannes Waldmann < waldmann@imn.htwk-leipzig.de> wrote:

...

and then read with my own parse string:"%Y-%m-%d %T%Q" This seems to work just fine.

Thanks. - When I'm using that format string, I get:

Convertible: error converting source data SqlLocalTime 2008-10-29 00:00:00 of type SqlValue to type Data.Time.LocalTime.LocalTime.ZonedTime: incompatible types

I guess I need to find out who wants ZonedTime.

In my DB description (generated by dbdirect), the only time-related type is CalendarTime.

J.

Did you append an empty string in the SELECT statement? If you append the empty string (||''), HDBC treats the field as text and so returns a SqlByteString. However, if you do not append the empty string, it treats the field as a timestamp and tries to convert it before it even reaches your code.

All of this is just speculation, of course, since I haven't actually looked at the code. But my "extensive" (ie, 5 minute) testing implies it to be true. Michael

...

...

...

...

"Johannes" == Johannes Waldmann writes:

Johannes> Michael Snoyman writes: >> Did you append an empty string in the SELECT statement? Johannes> Magnus says 1. is wrong, but I don't see how the DB server Johannes> could be convinced to send the ...T...Z format. In my Johannes> application, the table definition contains 'timestamp Johannes> without time zone' and I cannot change that. That is exactly the problem - it is wrong for CalendarT. -- Colin Adams Preston Lancashire

On Thu, Feb 04, 2010 at 09:26:43AM +0100, Günther Schmidt wrote:

I think you are looking for HaskellDB, you can find it on hackage. I've been working with it myself and can absolutely recommend it.

It is actively maintained by Justin Bailey.

It's been some time since I last tried HaskellDB but it used to generate SQL queries that no SGBD could ever optimize :D. Do you have better experiencies in the performance camp? Thanks, -- Felipe.