integrated skin code gor generating Sql Query (only left to execute it)
This commit is contained in:
Ruslan Talpa
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{-# LANGUAGE OverloadedStrings #-}
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module PostgREST.Functions
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where
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import PostgREST.Types
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import Control.Error
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import Data.List (find)
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import Data.Tree
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import Data.Text hiding (find, foldr, map, null, last)
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import Data.Monoid
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import PostgREST.PgQuery (pgFmtOperator, pgFmtValue, pgFmtIdent, pgFmtLit, fromQi, QualifiedIdentifier(..))
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findColumn :: [Column] -> Text -> Text -> Text -> Either Text Column
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findColumn allColumns s t c = note ("no such column: "<>t<>"."<>c) $
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find (\ col -> colSchema col == s && colTable col == t && colName col == c ) allColumns
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findTable :: [Table] -> Text -> Text -> Either Text Table
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findTable allTables s t = note ("no such table: "<>t) $
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find (\tb-> s == tableSchema tb && t == tableName tb ) allTables
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findRelation :: [Relation] -> Text -> Text -> Text -> Maybe Relation
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findRelation allRelations s t1 t2 =
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find (\r -> s == relSchema r && t1 == relTable r && t2 == relFTable r) allRelations
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filterToCondition :: Text -> [Column] -> Text -> Filter -> Either Text Condition
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filterToCondition schema allColumns table (Filter fld op val) =
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Condition <$> c <*> pure op <*> pure (VText (pack val))
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where
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c = (,) <$> column <*> pure (snd fld)
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column = findColumn allColumns schema table $ pack $ fst fld
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requestNodeToQuery ::Text -> [Table] -> [Column] -> RequestNode -> Either Text Query
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requestNodeToQuery schema allTables allColumns (RequestNode tblNameS flds fltrs) =
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Select <$> mainTable <*> select <*> joinTables <*> qwhere <*> rel
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where
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tblName = pack tblNameS
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mainTable = findTable allTables schema tblName
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select = mapM toDbSelectItem flds --besides specific columns, we allow * here also
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where
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-- it's ok not to check that the table exists here, mainTable will do the checking
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toDbSelectItem :: SelectItem -> Either Text DbSelectItem
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toDbSelectItem (("*", Nothing), Nothing) = Right $ ((Star{colSchema = schema, colTable = tblName}, Nothing), Nothing)
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toDbSelectItem ((c,jp), cast) = (,) <$> dbFld <*> pure cast
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where
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col = findColumn allColumns schema tblName $ pack c
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dbFld = (,) <$> col <*> pure jp
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qwhere = mapM (filterToCondition schema allColumns tblName) fltrs
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joinTables = pure []
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rel = pure Nothing
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addRelations :: [Relation] -> Maybe DbRequest -> DbRequest -> Either Text DbRequest
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addRelations allRelations parentNode node@(Node query@(Select {qMainTable=table}) forest) =
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case parentNode of
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Nothing -> Node query{qRelation=Nothing} <$> updatedForest
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(Just (Node (Select{qMainTable=parentTable}) _)) -> Node <$> (addRel query <$> rel) <*> updatedForest
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where
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rel = note ("no relation between " <> (tableName table) <> " and " <> (tableName parentTable)) $
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findRelation allRelations (tableSchema table) (tableName table) (tableName parentTable)
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addRel :: Query -> Relation -> Query
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addRel q r = q{qRelation = Just r}
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where
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updatedForest = mapM (addRelations allRelations (Just node)) forest
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addJoinConditions :: [Column] -> Tree Query -> Either Text DbRequest
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addJoinConditions allColumns (Node query@(Select{qRelation=relation}) forest) =
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case relation of
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Nothing -> Node <$> updatedQuery <*> updatedForest -- this is the root node
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Just rel@(Relation{relType="child"}) -> Node <$> (addCond <$> updatedQuery <*> getJoinCondition rel) <*> updatedForest
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Just (Relation{relType="parent"}) -> Node <$> updatedQuery <*> updatedForest
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-- Just (Many relationColumn1 relationColumn2) -> Node <$> pure updatedQuery{qJoinTables=linkTable:qJoinTables updatedQuery, qWhere=cond1:cond2:qWhere updatedQuery} <*> updatedForest
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-- where
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-- cond1 = getJoinCondition relationColumn1
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-- cond2 = getJoinCondition relationColumn2
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-- linkTable = Table "public" (colTable relationColumn1) True
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_ -> Left "unknow relation"
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where
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-- add parentTable and parentJoinConditions to the query
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updatedQuery = foldr (flip addCond) (query{qJoinTables = parentTables ++ (qJoinTables query)}) <$> parentJoinConditions
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where
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parentJoinConditions = mapM (getJoinCondition.snd) parents
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parentTables = map fst parents
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parents = mapMaybe (getParents.rootLabel) forest
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getParents qq@(Select{qRelation=(Just rel@(Relation{relType="parent"}))}) = Just (qMainTable qq, rel)
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getParents _ = Nothing
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updatedForest = mapM (addJoinConditions allColumns) forest
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getJoinCondition rel@(Relation s t c _ _ _) = Condition <$> cc <*> pure "=" <*> pure (VForeignKey rel)
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where
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col = findColumn allColumns s t c
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cc = (,) <$> col <*> pure Nothing
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addCond q con = q{qWhere=con:qWhere q}
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dbRequestToQuery :: DbRequest -> Text
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dbRequestToQuery (Node (Select mainTable columns tables conditions relation) forest) =
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case relation of
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Nothing -> "SELECT "
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<> "pg_catalog.count(t),"
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<> "array_to_json(array_agg(row_to_json(t)))::CHARACTER VARYING AS json "
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<> "FROM ("
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<> query
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<> ") t;"
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_ -> query
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where
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query = Data.Text.unwords [
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("WITH " <> intercalate ", " withs) `emptyOnNull` withs,
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"SELECT ", intercalate ", " (map selectItemToStr columns ++ selects),
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"FROM ", intercalate ", " (map pgFmtTable (mainTable:tables)),
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("WHERE " <> intercalate " AND " ( map pgFmtCondition conditions )) `emptyOnNull` conditions
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]
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emptyOnNull val x = if null x then "" else val
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(withs, selects) = foldr getQueryParts ([],[]) forest
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--getQueryParts is not total but dbRequestToQuery is called only after addJoinConditions which ensures the only
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--posible relations are Child Parent Many
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getQueryParts :: Tree Query -> ([Text], [Text]) -> ([Text], [Text])
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getQueryParts (Node q@(Select{qMainTable=table, qRelation=(Just (Relation {relType="child"}))}) forst) (w,s) = (w,sel:s)
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where name = tableName table
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sel = "("
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<> "SELECT array_to_json(array_agg(row_to_json("<>name<>"))) "
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<> "FROM (" <> dbRequestToQuery (Node q forst) <> ") " <> name
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<> ") AS " <> name
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getQueryParts (Node q@(Select{qMainTable=table, qRelation=(Just (Relation{relType="parent"}))}) forst) (w,s) = (wit:w,sel:s)
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where name = tableName table
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sel = "row_to_json(" <> name <> ".*) AS "<>name --TODO must be singular
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wit = name <> " AS ( " <> dbRequestToQuery (Node q forst) <> " )"
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-- getQueryParts (Node q@(Select{qMainTable=table, qRelation=(Just (Many _ _))}) forst) (w,s) = (w,sel:s)
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-- where name = tableName table
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-- sel = "("
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-- <> "SELECT array_to_json(array_agg(row_to_json("<>name<>"))) "
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-- <> "FROM (" <> dbRequestToQuery (Node q forst) <> ") " <> name
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-- <> ") AS " <> name
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-- the following is just to remove the warning, maybe relType should not be String?
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getQueryParts (Node (Select{qRelation=Nothing}) _) _ = undefined
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getQueryParts (Node (Select{qRelation=(Just (Relation {relType=_}))}) _) _ = undefined
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pgFmtCondition :: Condition -> Text
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pgFmtCondition (Condition (col,jp) ops val) = pgFmtColumn col <> pgFmtJsonPath jp <> opToStr op <> valToStr val
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where
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op = pack ops
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opToStr o = pgFmtOperator o
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valToStr v = case v of
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VText s -> pgFmtValue op s
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VForeignKey (Relation{relFTable=table, relFColumn=column}) -> table <> "." <> column
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pgFmtColumn :: Column -> Text
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pgFmtColumn Column {colSchema=s, colTable=t, colName=c} = pgFmtIdent s <> "." <> pgFmtIdent t <> "." <> pgFmtIdent c
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pgFmtColumn Star {colSchema=s, colTable=t} = pgFmtIdent s <> "." <> pgFmtIdent t <> ".*"
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pgFmtJsonPath :: Maybe JsonPath -> Text
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pgFmtJsonPath (Just [x]) = "->>" <> (pgFmtLit $ pack x)
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pgFmtJsonPath (Just (x:xs)) = "->" <> pgFmtLit (pack x) <> pgFmtJsonPath ( Just xs )
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pgFmtJsonPath _ = ""
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pgFmtTable :: Table -> Text
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pgFmtTable Table{tableSchema=s, tableName=n} = fromQi $ QualifiedIdentifier s n
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selectItemToStr :: DbSelectItem -> Text
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selectItemToStr ((c, jp), Nothing) = pgFmtColumn c <> pgFmtJsonPath jp <> asJsonPath jp
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selectItemToStr ((c, jp), Just cast ) = "CAST (" <> pgFmtColumn c <> pgFmtJsonPath jp <> " AS " <> pack cast <> " )" <> asJsonPath jp
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asJsonPath :: Maybe JsonPath -> Text
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asJsonPath Nothing = ""
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asJsonPath (Just xx) = " AS " <> (pack $ last xx)
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