[web-devel] [Yesod][Persist] Like keyword

[Michael Snoyman]

True, it *would* be better, but it can't fit in with the way
persistent works (AFAICT). Let's say that we're dealing with a
persistent entity:

Person
    name String Eq Like
    age Int

I now have a PersonNameLike constructor, *regardless of backend*. I
don't really think that throwing an exception will be necessary,
however: most likely, backends like redis can just implement this
functionality in Haskell itself. Performance won't be great, but those
are things you'll need to be aware of.

I suppose another possibility would be to allow some kind of generic
"add to query" and then you could write whatever kind of where clause
you want.

Michael

2010/12/22 Max Cantor <mxcantor at gmail.com>:
> Perhaps instead of throwing an exception, you add a typeclass PersistBackendLikeQuery or something where only backends that can handle like queries provide that typeclass.  seems better and much more haskellish than tossing an exception.
>
> Max
>
> On Dec 21, 2010, at 6:43 PM, Michael Snoyman wrote:
>
>> I've also wanted this at times. I'm a little wary of including it,
>> since it is very SQL-specific. On the other hand, it might be
>> reasonable to allow it in, and then non-SQL backends can either ignore
>> it, throw an exception, or try to implement it somehow. Does anyone
>> have any thoughts on this?
>>
>> Michael
>>
>> 2010/12/21 いとうかつとし <cutsea110 at gmail.com>:
>>> Hi
>>> continuously another request...
>>> I'd like to write "Like" keyword for using as Filter.
>>> this isn't supported yet, is this?
>>>
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>>> http://www.haskell.org/mailman/listinfo/web-devel
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>>>
>>
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