Merge pull request #35 from emdash/select_distinct

Add a `SELECT_DISTINCT` query variant

src/Sqlite3/Cmd.idr

@@ -349,6 +349,7 @@ record Query (t : Type) where
   [noHints]
   constructor Q
   {auto fromRow : FromRow t}
+  distinct      : Bool
   schema        : Schema
   from          : From schema
   columns       : LAll (NamedExpr schema) (FromRowTypes t)
@@ -376,7 +377,16 @@ SELECT :
   -> LAll (NamedExpr s) (FromRowTypes t)
   -> From s
   -> Query t
-SELECT xs from = Q s from xs TRUE TRUE [] [] Nothing 0
+SELECT xs from = Q False s from xs TRUE TRUE [] [] Nothing 0
+
+public export %inline
+SELECT_DISTINCT :
+     {s : _}
+  -> {auto fromRow : FromRow t}
+  -> LAll (NamedExpr s) (FromRowTypes t)
+  -> From s
+  -> Query t
+SELECT_DISTINCT xs from = Q True s from xs TRUE TRUE [] [] Nothing 0
 
 public export %inline
 GROUP_BY : (q : Query t) -> List (GroupingTerm $ ExprSchema q.columns) -> Query t

src/Sqlite3/Parameter.idr

@@ -318,11 +318,14 @@ encodeHaving x    = do
 ||| inserted as placeholders for literal values where appropriate.
 export
 encodeQuery : Query ts -> ParamStmt
-encodeQuery (Q _ from vs where_ having group_by order_by lim off) = do
+encodeQuery (Q distinct _ from vs where_ having group_by order_by lim off) = do
   vstr <- namedExprs [<] vs
   fstr <- encodeFrom from
   wh   <- encodeExprP where_
   hav  <- encodeHaving having
   grp  <- encodeOrd "GROUP BY" (map ord group_by)
   ord  <- encodeOrd "ORDER BY" order_by
-  pure "SELECT \{vstr} \{fstr} WHERE \{wh} \{grp} \{hav} \{ord} \{limit lim off}"
+  let rest = "\{vstr} \{fstr} WHERE \{wh} \{grp} \{hav} \{ord} \{limit lim off}"
+  pure $ case distinct of
+    True  => "SELECT DISTINCT \{rest}"
+    False => "SELECT \{rest}"

test/src/Main.idr

@@ -34,6 +34,7 @@ app = withDB ":memory:" $ do
     , IF_NOT_EXISTS createFiles
     , IF_NOT_EXISTS createUnits
     , IF_NOT_EXISTS createEmployees
+    , IF_NOT_EXISTS createEdges
     , insertMol $ M "Ethanol"    (Just "64-17-5") (Just 46.069) Compound
     , insertMol $ M "Strychnine" (Just "57-24-9") (Just 334.419) Compound
     , insertMol $ M "Atropine"   (Just "51-55-8") (Just 289.375) Compound
@@ -55,6 +56,14 @@ app = withDB ":memory:" $ do
     , insertEmployee $ E "Gundi" 2050.0 1
     , insertEmployee $ E "Valeri" 5010.0 1
     , insertEmployee $ E "Ronja" 4010.0 1
+    , insertEdge "A" "B"
+    , insertEdge "B" "C"
+    , insertEdge "B" "D"
+    , insertEdge "C" "E"
+    , insertEdge "C" "F"
+    , insertEdge "D" "F"
+    , insertEdge "F" "G"
+    , insertEdge "B" "F"
     ] ++ fromList (insertFile . file <$> [0..255])
 
   queryTable (mol TRUE) 1000 >>= printTable
@@ -78,5 +87,7 @@ app = withDB ":memory:" $ do
   queryTable unitStats 1000 >>= printTable
   putStrLn ""
 
+  queryTable parents 1000 >>= printTable
+
 main : IO ()
 main = runApp handlers app

test/src/Schema.idr

@@ -48,6 +48,14 @@ Files =
     , C "content" BLOB
     ]
 
+public export
+Edges : SQLTable
+Edges =
+  table "edges"
+    [ C "u" TEXT
+    , C "v" TEXT
+    ]
+
 export
 createMolecules : Cmd TCreate
 createMolecules =
@@ -92,6 +100,15 @@ createEmployees =
     , UNIQUE ["name"]
     ]
 
+export
+createEdges : Cmd TCreate
+createEdges =
+  CREATE_TABLE Edges
+    [ PRIMARY_KEY ["u", "v"]
+    , NOT_NULL "u"
+    , NOT_NULL "v"
+    ]
+
 --------------------------------------------------------------------------------
 -- Idris Types
 --------------------------------------------------------------------------------
@@ -157,6 +174,10 @@ export
 insertFile : File -> Cmd TInsert
 insertFile = insert Files ["content"]
 
+export
+insertEdge : String -> String -> Cmd TInsert
+insertEdge u v = INSERT Edges ["u", "v"] [val u, val v]
+
 --------------------------------------------------------------------------------
 -- Query
 --------------------------------------------------------------------------------
@@ -232,3 +253,10 @@ tuples =
     ]
     `WHERE` ("m1.molweight" < "m2.molweight")
     `OFFSET` 2
+
+public export
+parents : LQuery [String]
+parents =
+  SELECT_DISTINCT
+    ["u"]
+    [< FROM $ Edges `AS` "e"]