[Haskell-cafe] Postgresql Intervals with Opaleye

[info at rotnetix.com]

Got it kind of working, for some reason the interval type in my postgres 
instance does not correspond to the parser from kqr but i managed to 
implement a version that kind of works.  More importantly the experience 
has been great for understanding how to do my own conversion types.  Thanks 
for the help.


On Saturday, January 3, 2015 9:53:31 PM UTC+11, Tom Ellis wrote:
>
> On Tue, Dec 30, 2014 at 04:59:29PM -0800, in... at rotnetix.com <javascript:> 
> wrote: 
> > That might be tricky... 
> >  See https://github.com/lpsmith/postgresql-simple/pull/115, it seems 
> like 
> > it is not trivial to get the conversions to haskell types correct. 
> > 
> > Look like I am back to native SQL for that one.   
>
> As lpsmith says here 
>
>     
> https://github.com/lpsmith/postgresql-simple/pull/115#issuecomment-48754627 
>
> you can use the attached patch in your own code to get a conversion from 
> `interval` to `DiffTime`.  It will have a few strange corner cases but you 
> will probably find you never hit them. 
>
> Once you've done that you can make them suitable for Opaleye by writing 
>
>     data PGInterval 
>
>     instance QueryRunnerColumnDefault PGInterval DiffTime where 
>           queryRunnerColumnDefault = fieldQueryRunnerColumn 
>
> (you may have to import something from Opaleye.Internal.RunQuery). 
>
> Please let me know how you get on with that, if you try it. 
>
> Tom 
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