graphql-engine/server/src-lib/Hasura/Backends/MSSQL/Meta.hs

-- |

module Hasura.Backends.MSSQL.Meta
  ( loadDBMetadata
  ) where

import           Hasura.Prelude

import qualified Data.ByteString.UTF8                  as BSUTF8
import qualified Data.HashMap.Strict                   as HM
import qualified Data.HashSet                          as HS
import qualified Data.Text                             as T
import qualified Data.Text.Encoding                    as T
import qualified Database.ODBC.SQLServer               as ODBC

import           Data.Aeson                            as Aeson
import           Data.FileEmbed                        (embedFile, makeRelativeToProject)
import           Data.String

import           Hasura.Backends.MSSQL.Connection
import           Hasura.Backends.MSSQL.Instances.Types ()
import           Hasura.Backends.MSSQL.Types
import           Hasura.Base.Error
import           Hasura.RQL.Types.Column
import           Hasura.RQL.Types.Common               (OID (..))
import           Hasura.RQL.Types.Table
import           Hasura.SQL.Backend


--------------------------------------------------------------------------------
-- Loader

loadDBMetadata
  :: (MonadError QErr m, MonadIO m)
  => MSSQLPool -> m (DBTablesMetadata 'MSSQL)
loadDBMetadata pool = do
  let
    queryBytes = $(makeRelativeToProject "src-rsr/mssql_table_metadata.sql" >>= embedFile)
    odbcQuery :: ODBC.Query = fromString . BSUTF8.toString $ queryBytes
  sysTablesText <- runJSONPathQuery pool odbcQuery
  case Aeson.eitherDecodeStrict (T.encodeUtf8 sysTablesText) of
    Left e          -> throw500 $ T.pack $ "error loading sql server database schema: " <> e
    Right sysTables -> pure $ HM.fromList $ map transformTable sysTables

--------------------------------------------------------------------------------
-- Local types

data SysTable = SysTable
  { staName            :: Text
  , staObjectId        :: Int
  , staJoinedSysColumn :: [SysColumn]
  , staJoinedSysSchema :: SysSchema
  } deriving (Show, Generic)

instance FromJSON SysTable where
  parseJSON = genericParseJSON hasuraJSON


data SysSchema = SysSchema
  { ssName     :: Text
  , ssSchemaId :: Int
  } deriving (Show, Generic)

instance FromJSON SysSchema where
  parseJSON = genericParseJSON hasuraJSON


data SysColumn = SysColumn
  { scName                    :: Text
  , scColumnId                :: Int
  , scUserTypeId              :: Int
  , scIsNullable              :: Bool
  , scIsIdentity              :: Bool
  , scJoinedSysType           :: SysType
  , scJoinedForeignKeyColumns :: [SysForeignKeyColumn]
  } deriving (Show, Generic)
instance FromJSON SysColumn where
  parseJSON = genericParseJSON hasuraJSON

data SysType = SysType
  { styName       :: Text
  , stySchemaId   :: Int
  , styUserTypeId :: Int
  } deriving (Show, Generic)

instance FromJSON SysType where
  parseJSON = genericParseJSON hasuraJSON


data SysForeignKeyColumn = SysForeignKeyColumn
  { sfkcConstraintObjectId         :: Int
  , sfkcConstraintColumnId         :: Int
  , sfkcParentObjectId             :: Int
  , sfkcParentColumnId             :: Int
  , sfkcReferencedObjectId         :: Int
  , sfkcReferencedColumnId         :: Int
  , sfkcJoinedReferencedTableName  :: Text
  , sfkcJoinedReferencedColumnName :: Text
  , sfkcJoinedReferencedSysSchema  :: SysSchema
  } deriving (Show, Generic)

instance FromJSON SysForeignKeyColumn where
  parseJSON = genericParseJSON hasuraJSON


--------------------------------------------------------------------------------
-- Transform

transformTable :: SysTable -> (TableName, DBTableMetadata 'MSSQL)
transformTable tableInfo =
  let schemaName = ssName $ staJoinedSysSchema tableInfo
      tableName  = TableName (staName tableInfo) schemaName
      tableOID   = OID $ staObjectId tableInfo
      (columns, foreignKeys) = unzip $ transformColumn <$> staJoinedSysColumn tableInfo
      foreignKeysMetadata = HS.fromList $ map ForeignKeyMetadata $ coalesceKeys $ concat foreignKeys
      identityColumns = map (ColumnName . scName) $
                        filter scIsIdentity $ staJoinedSysColumn tableInfo
  in ( tableName
     , DBTableMetadata
       tableOID
       columns
       Nothing  -- no primary key information?
       HS.empty -- no unique constraints?
       foreignKeysMetadata
       Nothing  -- no views, only tables
       Nothing  -- no description
       identityColumns
     )

transformColumn
  :: SysColumn
  -> (RawColumnInfo 'MSSQL, [ForeignKey 'MSSQL])
transformColumn columnInfo =
  let prciName        = ColumnName $ scName columnInfo
      prciPosition    = scColumnId columnInfo
      -- ^ the IR uses this to uniquely identify columns, as Postgres will
      -- keep a unique position for a column even when columns are added
      -- or dropped. We assume here that this arbitrary column id can
      -- serve the same purpose.
      prciIsNullable  = scIsNullable columnInfo
      prciDescription = Nothing
      prciType = parseScalarType $ styName $ scJoinedSysType columnInfo
      foreignKeys = scJoinedForeignKeyColumns columnInfo <&> \foreignKeyColumn ->
        let _fkConstraint    = Constraint () $ OID $ sfkcConstraintObjectId foreignKeyColumn
            -- ^ constraints have no name in MSSQL, and are uniquely identified by their OID
            schemaName       = ssName $ sfkcJoinedReferencedSysSchema foreignKeyColumn
            _fkForeignTable  = TableName (sfkcJoinedReferencedTableName foreignKeyColumn) schemaName
            _fkColumnMapping = HM.singleton prciName $ ColumnName $ sfkcJoinedReferencedColumnName foreignKeyColumn
        in ForeignKey {..}
  in (RawColumnInfo{..}, foreignKeys)


--------------------------------------------------------------------------------
-- Helpers

coalesceKeys :: [ForeignKey 'MSSQL] -> [ForeignKey 'MSSQL]
coalesceKeys = HM.elems . foldl' coalesce HM.empty
  where
    coalesce mapping fk@(ForeignKey constraint tableName _) = HM.insertWith combine (constraint, tableName) fk mapping
    combine oldFK newFK = oldFK { _fkColumnMapping = (HM.union `on` _fkColumnMapping) oldFK newFK }

parseScalarType :: Text -> ScalarType
parseScalarType = \case
  "char"             -> CharType
  "numeric"          -> NumericType
  "decimal"          -> DecimalType
  "money"            -> DecimalType
  "smallmoney"       -> DecimalType
  "int"              -> IntegerType
  "smallint"         -> SmallintType
  "float"            -> FloatType
  "real"             -> RealType
  "date"             -> DateType
  "time"             -> Ss_time2Type
  "varchar"          -> VarcharType
  "nchar"            -> WcharType
  "nvarchar"         -> WvarcharType
  "ntext"            -> WtextType
  "timestamp"        -> TimestampType
  "text"             -> TextType
  "binary"           -> BinaryType
  "bigint"           -> BigintType
  "tinyint"          -> TinyintType
  "varbinary"        -> VarbinaryType
  "bit"              -> BitType
  "uniqueidentifier" -> GuidType
  "geography"        -> GeographyType
  "geometry"         -> GeometryType
  t                  -> UnknownType t