Hi all, I'm running into significant compile-time performance problems with a relatively simple database. This email describes a small example using a default project from the yesod scaffolding tool. Trying to compile the project causes ghc to consume several GB of memory on my system (eventually I have to kill it). I'm running GHC 7.0.3 and the current yesod beta. It's definitely possible that I'm doing something very stupid - any help would be appreciated. The example just involves adding one table to a default project's database. Suppose I want to add a table with 15 columns, each holding a US State or Nothing (a little silly, but in my real application the data is more interesting). To do this, I'll make a datatype to list the US states, give it a PersistField instance with some help from the Enum typeclass, and add the table. In the Model.hs file, I add an import line:
import Database.Persist.Base
And then I define my representation of the US State codes:
data USStateCode = AL | AK | AS | AZ | AR | CA | CO | CT | DE | DC | FM | FL | GA | GU | HI | ID | IL | IN | IA | KS | KY | LA | ME | MD | MA | MI | MN | MS | MO | MT | NE | NV | NH | NJ | NM | NY | NC | ND | MP | OH | OK | OR | PW | PA | PR | RI | SC | SD | TN | TX | UT | VT | VI | VA | WA | WV | WI | WY deriving (Read, Show, Eq, Ord, Enum)
instance PersistField USStateCode where toPersistValue = PersistInt64 . toEnum . fromEnum
fromPersistValue (PersistInt64 a) = Right $ toEnum $ fromEnum a fromPersistValue _ = Left "error"
sqlType _ = SqlInteger
And I add the table to the bottom of my entities file:
MyTable st1 USStateCode Maybe st2 USStateCode Maybe st3 USStateCode Maybe st4 USStateCode Maybe st5 USStateCode Maybe st6 USStateCode Maybe st7 USStateCode Maybe st8 USStateCode Maybe st9 USStateCode Maybe st10 USStateCode Maybe st11 USStateCode Maybe st12 USStateCode Maybe st13 USStateCode Maybe st14 USStateCode Maybe st15 USStateCode Maybe
Making these changes to a default project and then compiling causes the problems I described above. Can someone fill me on on a better way to add a table holding some enumerated data? Thanks! --Chris