[Haskelldb-users] HaskellDB efficience

[Krasimir A. <ka2...@ya...>]

   Hi, 

I interested to see the generated SQL code from
HaskellDB. The first step was to write very simple
example:

import Database.HaskellDB
import Database.HaskellDB.Query
import Database.HaskellDB.Sql
import Database.HaskellDB.GenericConnect
import Text.PrettyPrint
import Testdb.Documents

main = do
  let primQuery = runQuery $ do
	       docs <- table documents
	       project (docDate << docs!docDate)
  putStrLn (render (ppSql (toSql primQuery)))

When the example was executed I got:

SELECT DISTINCT docDate2 as docDate
FROM  (SELECT DISTINCT docDate1 as docDate2,
                       id1,
                       docDate1,
                       creationDate1
       FROM  (SELECT DISTINCT id as id1,
                              docDate as docDate1,
                              creationDate as
creationDate1
              FROM  documents as T1) as T1) as T1

I am surprised from this very complicated and
inefficient code. What is the reason to have these
nested "DISTICT" statements? I expected to see just
something like:

select docDate from documents

Regards,
  Krasimir



		
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