Hi, I have an idea to extend Relation types and Record types into tuple-ed ones.
I wrote experimentally implementation to achieve this.
https://github.com/khibino/haskelldb/tree/tuple_join
Query of single table case is like below.
type RelX = RecCons X0 (Expr p0) (RecCons X1 ... )
tableX :: Table RelX
...
type RecordX = RecCons X0 p0 (RecCons X1 ... )
single :: Query (Rel RelX)
single = do
tx <- table tableX
...
project $ copyAll tx
querySingle :: Database -> IO [Record RecordX]
querySingle = (`query` single)
As usual, joined query case, we have been required to re-compose joined type other than defined Relation and Record types.
type RelY = RecCons Y0 (Expr q0) (RecCons Y1 ... )
tableY :: Table RelY
...
type RelJoined = RecCons X0 (Expr p0) ( ... (RecCons Y0 (Expr q0) ... ) ... )
type RecordJoined = RecCons X0 p0 ( ... (RecCons Y0 q0 ... ) ... )
joined' :: Query (Rel Joined)
joined' = do
tx <- table tableX
ty <- table tableY
...
project
$ copy x0 tx
# copy x1 tx
...
# copy y0 ty
# copy y0 ty
...
queryJoined' :: Database -> IO [Record RecordJoined]
queryJoined' = (`query` joined')
On my implementation, we can simply use tuple type in joined query case.
Not required to re-compose joined Reltion and Record types.
type RecordY = RecCons Y0 q0 (RecCons Y1 ... )
joined :: Query (Rel (RelX, RelY))
joined = do
tx <- table tableX
ty <- table tableY
...
project
$ (,) <$> copyAll tx
<*> copyAll ty
queryJoined :: Database -> IO [Record (RecordX, RecordY)]
queryJoined = (`query` joined)
--
-- Kei Hibino
-- ex8...@gm...
--
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