graphql-engine/server/src-lib/Hasura/Backends/MSSQL/Instances/Execute.hs
2021-11-22 09:12:45 +00:00

669 lines
26 KiB
Haskell

{-# OPTIONS_GHC -fno-warn-orphans #-}
module Hasura.Backends.MSSQL.Instances.Execute
( MultiplexedQuery' (..),
multiplexRootReselect,
)
where
import Control.Monad.Trans.Control (MonadBaseControl)
import Control.Monad.Validate qualified as V
import Data.Aeson.Extended qualified as J
import Data.HashMap.Strict qualified as Map
import Data.HashMap.Strict.InsOrd qualified as OMap
import Data.HashSet qualified as Set
import Data.List.NonEmpty qualified as NE
import Data.Text.Extended qualified as T
import Database.MSSQL.Transaction qualified as Tx
import Database.ODBC.Internal qualified as ODBCI
import Database.ODBC.SQLServer qualified as ODBC
import Hasura.Backends.MSSQL.Connection
import Hasura.Backends.MSSQL.FromIr as TSQL
import Hasura.Backends.MSSQL.Plan
import Hasura.Backends.MSSQL.SQL.Value (txtEncodedColVal)
import Hasura.Backends.MSSQL.ToQuery as TQ
import Hasura.Backends.MSSQL.Types as TSQL
import Hasura.Base.Error
import Hasura.EncJSON
import Hasura.GraphQL.Execute.Backend
import Hasura.GraphQL.Execute.LiveQuery.Plan
import Hasura.GraphQL.Namespace (RootFieldAlias (..), RootFieldMap)
import Hasura.GraphQL.Parser
import Hasura.Prelude
import Hasura.RQL.IR
import Hasura.RQL.IR qualified as IR
import Hasura.RQL.Types
import Hasura.RQL.Types qualified as RQLTypes
import Hasura.RQL.Types.Column qualified as RQLColumn
import Hasura.SQL.AnyBackend qualified as AB
import Hasura.Session
import Language.GraphQL.Draft.Syntax qualified as G
instance BackendExecute 'MSSQL where
type PreparedQuery 'MSSQL = Text
type MultiplexedQuery 'MSSQL = MultiplexedQuery'
type ExecutionMonad 'MSSQL = ExceptT QErr IO
mkDBQueryPlan = msDBQueryPlan
mkDBMutationPlan = msDBMutationPlan
mkDBSubscriptionPlan = msDBSubscriptionPlan
mkDBQueryExplain = msDBQueryExplain
mkLiveQueryExplain = msDBLiveQueryExplain
-- NOTE: Currently unimplemented!.
--
-- This function is just a stub for future implementation; for now it just
-- throws a 500 error.
mkDBRemoteRelationshipPlan =
msDBRemoteRelationshipPlan
-- Multiplexed query
newtype MultiplexedQuery' = MultiplexedQuery' Reselect
instance T.ToTxt MultiplexedQuery' where
toTxt (MultiplexedQuery' reselect) = T.toTxt $ toQueryPretty $ fromReselect reselect
-- Query
msDBQueryPlan ::
forall m.
( MonadError QErr m
) =>
UserInfo ->
SourceName ->
SourceConfig 'MSSQL ->
QueryDB 'MSSQL (Const Void) (UnpreparedValue 'MSSQL) ->
m (DBStepInfo 'MSSQL)
msDBQueryPlan userInfo sourceName sourceConfig qrf = do
-- TODO (naveen): Append Query Tags to the query
let sessionVariables = _uiSession userInfo
statement <- planQuery sessionVariables qrf
let printer = fromSelect statement
queryString = ODBC.renderQuery $ toQueryPretty printer
pool = _mscConnectionPool sourceConfig
odbcQuery = encJFromText <$> runJSONPathQuery pool (toQueryFlat printer)
pure $ DBStepInfo @'MSSQL sourceName sourceConfig (Just queryString) odbcQuery
runShowplan ::
ODBC.Query -> ODBC.Connection -> IO [Text]
runShowplan query conn = do
ODBC.exec conn "SET SHOWPLAN_TEXT ON"
texts <- ODBC.query conn query
ODBC.exec conn "SET SHOWPLAN_TEXT OFF"
-- we don't need to use 'finally' here - if an exception occurs,
-- the connection is removed from the resource pool in 'withResource'.
pure texts
msDBQueryExplain ::
MonadError QErr m =>
RootFieldAlias ->
UserInfo ->
SourceName ->
SourceConfig 'MSSQL ->
QueryDB 'MSSQL (Const Void) (UnpreparedValue 'MSSQL) ->
m (AB.AnyBackend DBStepInfo)
msDBQueryExplain fieldName userInfo sourceName sourceConfig qrf = do
let sessionVariables = _uiSession userInfo
statement <- planQuery sessionVariables qrf
let query = toQueryPretty (fromSelect statement)
queryString = ODBC.renderQuery query
pool = _mscConnectionPool sourceConfig
odbcQuery =
withMSSQLPool
pool
( \conn -> liftIO do
showplan <- runShowplan query conn
pure
( encJFromJValue $
ExplainPlan
fieldName
(Just queryString)
(Just showplan)
)
)
pure $
AB.mkAnyBackend $
DBStepInfo @'MSSQL sourceName sourceConfig Nothing odbcQuery
msDBLiveQueryExplain ::
(MonadIO m, MonadBaseControl IO m, MonadError QErr m) =>
LiveQueryPlan 'MSSQL (MultiplexedQuery 'MSSQL) ->
m LiveQueryPlanExplanation
msDBLiveQueryExplain (LiveQueryPlan plan sourceConfig variables _) = do
let (MultiplexedQuery' reselect) = _plqpQuery plan
query = toQueryPretty $ fromSelect $ multiplexRootReselect [(dummyCohortId, variables)] reselect
pool = _mscConnectionPool sourceConfig
explainInfo <- withMSSQLPool pool (liftIO . runShowplan query)
pure $ LiveQueryPlanExplanation (T.toTxt query) explainInfo variables
--------------------------------------------------------------------------------
-- Producing the correct SQL-level list comprehension to multiplex a query
-- Problem description:
--
-- Generate a query that repeats the same query N times but with
-- certain slots replaced:
--
-- [ Select x y | (x,y) <- [..] ]
--
multiplexRootReselect ::
[(CohortId, CohortVariables)] ->
TSQL.Reselect ->
TSQL.Select
multiplexRootReselect variables rootReselect =
emptySelect
{ selectTop = NoTop,
selectProjections =
[ FieldNameProjection
Aliased
{ aliasedThing =
TSQL.FieldName
{ fieldNameEntity = rowAlias,
fieldName = resultIdAlias
},
aliasedAlias = resultIdAlias
},
ExpressionProjection
Aliased
{ aliasedThing =
ColumnExpression
( TSQL.FieldName
{ fieldNameEntity = resultAlias,
fieldName = TSQL.jsonFieldName
}
),
aliasedAlias = resultAlias
}
],
selectFrom =
Just $
FromOpenJson
Aliased
{ aliasedThing =
OpenJson
{ openJsonExpression =
ValueExpression (ODBC.TextValue $ lbsToTxt $ J.encode variables),
openJsonWith =
Just $
NE.fromList
[ UuidField resultIdAlias (Just $ IndexPath RootPath 0),
JsonField resultVarsAlias (Just $ IndexPath RootPath 1)
]
},
aliasedAlias = rowAlias
},
selectJoins =
[ Join
{ joinSource = JoinReselect rootReselect,
joinJoinAlias =
JoinAlias
{ joinAliasEntity = resultAlias,
joinAliasField = Just TSQL.jsonFieldName
}
}
],
selectWhere = Where mempty,
selectFor =
JsonFor ForJson {jsonCardinality = JsonArray, jsonRoot = NoRoot},
selectOrderBy = Nothing,
selectOffset = Nothing
}
-- mutation
msDBMutationPlan ::
forall m.
( MonadError QErr m
) =>
UserInfo ->
Bool ->
SourceName ->
SourceConfig 'MSSQL ->
MutationDB 'MSSQL (Const Void) (UnpreparedValue 'MSSQL) ->
m (DBStepInfo 'MSSQL)
msDBMutationPlan userInfo stringifyNum sourceName sourceConfig mrf = do
go <$> case mrf of
MDBInsert annInsert -> executeInsert userInfo stringifyNum sourceConfig annInsert
MDBDelete annDelete -> executeDelete userInfo stringifyNum sourceConfig annDelete
MDBFunction {} -> throw400 NotSupported "function mutations are not supported in MSSQL"
where
go v = DBStepInfo @'MSSQL sourceName sourceConfig Nothing v
-- | Execution of a MSSQL insert mutation broadly involves two steps.
--
-- -- insert_table(objects: [
-- -- {column1: value1, column2: value2},
-- -- {column1: value3, column2: value4}
-- -- ]
-- -- ){
-- -- affected_rows
-- -- returning {
-- -- column1
-- -- column2
-- -- }
-- -- }
-- --
-- Step 1: Inserting rows into the table
-- --
-- -- a. Generate an SQL Insert statement from the GraphQL insert mutation with OUTPUT expression to return
-- -- primary key column values after insertion.
-- -- b. Before insert, Set IDENTITY_INSERT to ON if any insert row contains atleast one identity column.
-- --
-- -- SET IDENTITY_INSERT some_table ON;
-- -- INSERT INTO some_table (column1, column2) OUTPUT INSERTED.pkey_column1, INSERTED.pkey_column2 VALUES (value1, value2), (value3, value4);
-- --
-- Step 2: Generation of the mutation response
-- --
-- -- An SQL statement is generated and when executed it returns the mutation selection set containing 'affected_rows' and 'returning' field values.
-- -- The statement is generated with multiple sub select queries explained below:
-- --
-- -- a. A SQL Select statement to fetch only inserted rows from the table using primary key column values fetched from
-- -- Step 1 in the WHERE clause
-- --
-- -- <table_select> :=
-- -- SELECT * FROM some_table WHERE (pkey_column1 = value1 AND pkey_column2 = value2) OR (pkey_column1 = value3 AND pkey_column2 = value4)
-- --
-- -- The above select statement is referred through a common table expression - "WITH [with_alias] AS (<table_select>)"
-- --
-- -- b. The 'affected_rows' field value is obtained by using COUNT aggregation and the 'returning' field selection set is translated to
-- -- a SQL select statement using @'mkSQLSelect'.
-- --
-- -- <mutation_output_select> :=
-- -- SELECT (SELECT COUNT(*) FROM [with_alias]) AS [affected_rows], (select_from_returning) AS [returning] FOR JSON PATH, INCLUDE_NULL_VALUES, WITHOUT_ARRAY_WRAPPER
-- --
-- -- c. Evaluate the check constraint using CASE expression. We use SUM aggregation to check if any inserted row has failed the check constraint.
-- --
-- -- <check_constraint_select> :=
-- -- SELECT SUM(CASE WHEN <check_boolean_expression> THEN 0 ELSE 1 END) FROM [with_alias]
-- --
-- -- d. The final select statement look like
-- --
-- -- WITH "with_alias" AS (<table_select>)
-- -- SELECT (<mutation_output_select>) AS [mutation_response], (<check_constraint_select>) AS [check_constraint_select]
-- --
-- -- When executed, the above statement returns a single row with mutation response as a string value and check constraint result as an integer value.
executeInsert ::
MonadError QErr m =>
UserInfo ->
Bool ->
SourceConfig 'MSSQL ->
AnnInsert 'MSSQL (Const Void) (UnpreparedValue 'MSSQL) ->
m (ExceptT QErr IO EncJSON)
executeInsert userInfo stringifyNum sourceConfig annInsert = do
-- Convert the leaf values from @'UnpreparedValue' to sql @'Expression'
insert <- traverse (prepareValueQuery sessionVariables) annInsert
let insertTx = buildInsertTx insert
pure $ withMSSQLPool pool $ Tx.runTxE fromMSSQLTxError insertTx
where
sessionVariables = _uiSession userInfo
pool = _mscConnectionPool sourceConfig
table = _aiTableName $ _aiData annInsert
withSelectTableAlias = "t_" <> tableName table
withAlias = "with_alias"
buildInsertTx :: AnnInsert 'MSSQL (Const Void) Expression -> Tx.TxET QErr IO EncJSON
buildInsertTx insert = do
let identityColumns = _mssqlIdentityColumns $ _aiExtraInsertData $ _aiData insert
insertColumns = concatMap (map fst . getInsertColumns) $ _aiInsObj $ _aiData insert
-- Set identity insert to ON if insert object contains identity columns
when (any (`elem` identityColumns) insertColumns) $
Tx.unitQueryE fromMSSQLTxError $
toQueryFlat $
TQ.fromSetIdentityInsert $
SetIdentityInsert (_aiTableName $ _aiData insert) SetON
-- Generate the INSERT query
let insertQuery = toQueryFlat $ TQ.fromInsert $ TSQL.fromInsert insert
fromODBCException e =
(err400 MSSQLError "insert query exception") {qeInternal = Just (ExtraInternal $ odbcExceptionToJSONValue e)}
-- Execute the INSERT query and fetch the primary key values
primaryKeyValues <- Tx.buildGenericTxE fromODBCException $ \conn -> ODBCI.query conn (ODBC.renderQuery insertQuery)
let withSelect = generateWithSelect primaryKeyValues
-- WITH [with_alias] AS (select_query)
withExpression = With $ pure $ Aliased withSelect withAlias
mutationOutputSelect <- mkMutationOutputSelect stringifyNum withAlias $ _aiOutput insert
let (checkCondition, _) = _aiCheckCond $ _aiData insert
-- The check constraint is translated to boolean expression
checkBoolExp <-
V.runValidate (runFromIr $ runReaderT (fromGBoolExp checkCondition) (EntityAlias withAlias))
`onLeft` (throw500 . tshow)
-- SELECT (<mutation_output_select>) AS [mutation_response], (<check_constraint_select>) AS [check_constraint_select]
let mutationOutputCheckConstraintSelect = selectMutationOutputAndCheckCondition mutationOutputSelect checkBoolExp
-- WITH "with_alias" AS (<table_select>)
-- SELECT (<mutation_output_select>) AS [mutation_response], (<check_constraint_select>) AS [check_constraint_select]
finalSelect = mutationOutputCheckConstraintSelect {selectWith = Just withExpression}
(responseText, checkConditionInt) <- Tx.singleRowQueryE fromMSSQLTxError (toQueryFlat $ TQ.fromSelect finalSelect)
unless (checkConditionInt == (0 :: Int)) $
throw400 PermissionError "check constraint of an insert permission has failed"
pure $ encJFromText responseText
columnFieldExpression :: ODBCI.Column -> Expression
columnFieldExpression column =
ColumnExpression $ TSQL.FieldName (ODBCI.columnName column) withSelectTableAlias
generateWithSelect :: [[(ODBCI.Column, ODBC.Value)]] -> Select
generateWithSelect pkeyValues =
emptySelect
{ selectProjections = [StarProjection],
selectFrom = Just $ FromQualifiedTable $ Aliased table withSelectTableAlias,
selectWhere = whereExpression
}
where
-- WHERE (column1 = value1 AND column2 = value2) OR (column1 = value3 AND column2 = value4)
whereExpression =
let mkColumnEqExpression (column, value) =
OpExpression EQ' (columnFieldExpression column) (ValueExpression value)
in Where $ pure $ OrExpression $ map (AndExpression . map mkColumnEqExpression) pkeyValues
generateCheckConstraintSelect :: Expression -> Select
generateCheckConstraintSelect checkBoolExp =
let zeroValue = ValueExpression $ ODBC.IntValue 0
oneValue = ValueExpression $ ODBC.IntValue 1
caseExpression = ConditionalExpression checkBoolExp zeroValue oneValue
sumAggregate = OpAggregate "SUM" [caseExpression]
in emptySelect
{ selectProjections = [AggregateProjection (Aliased sumAggregate "check")],
selectFrom = Just $ TSQL.FromIdentifier withAlias
}
selectMutationOutputAndCheckCondition :: Select -> Expression -> Select
selectMutationOutputAndCheckCondition mutationOutputSelect checkBoolExp =
let mutationOutputProjection =
ExpressionProjection $ Aliased (SelectExpression mutationOutputSelect) "mutation_response"
checkConstraintProjection =
ExpressionProjection $ Aliased (SelectExpression (generateCheckConstraintSelect checkBoolExp)) "check_constraint_select"
in emptySelect {selectProjections = [mutationOutputProjection, checkConstraintProjection]}
-- Delete
-- | Executes a Delete IR AST and return results as JSON.
executeDelete ::
MonadError QErr m =>
UserInfo ->
Bool ->
SourceConfig 'MSSQL ->
AnnDelG 'MSSQL (Const Void) (UnpreparedValue 'MSSQL) ->
m (ExceptT QErr IO EncJSON)
executeDelete userInfo stringifyNum sourceConfig deleteOperation = do
preparedDelete <- traverse (prepareValueQuery $ _uiSession userInfo) deleteOperation
let pool = _mscConnectionPool sourceConfig
pure $ withMSSQLPool pool $ Tx.runTxE fromMSSQLTxError (buildDeleteTx preparedDelete stringifyNum)
-- | Converts a Delete IR AST to a transaction of three delete sql statements.
--
-- A GraphQL delete mutation does two things:
--
-- 1. Deletes rows in a table according to some predicate
-- 2. (Potentially) returns the deleted rows (including relationships) as JSON
--
-- In order to complete these 2 things we need 3 SQL statements:
--
-- 1. SELECT INTO <temp_table> WHERE <false> - creates a temporary table
-- with the same schema as the original table in which we'll store the deleted rows
-- from the table we are deleting
-- 2. DELETE FROM with OUTPUT - deletes the rows from the table and inserts the
-- deleted rows to the temporary table from (1)
-- 3. SELECT - constructs the @returning@ query from the temporary table, including
-- relationships with other tables.
buildDeleteTx ::
AnnDel 'MSSQL ->
Bool ->
Tx.TxET QErr IO EncJSON
buildDeleteTx deleteOperation stringifyNum = do
let withAlias = "with_alias"
createTempTableQuery =
toQueryFlat $
TQ.fromSelectIntoTempTable $
TSQL.toSelectIntoTempTable tempTableNameDeleted (dqp1Table deleteOperation) (dqp1AllCols deleteOperation)
-- Create a temp table
Tx.unitQueryE fromMSSQLTxError createTempTableQuery
let deleteQuery = TQ.fromDelete <$> TSQL.fromDelete deleteOperation
deleteQueryValidated <- toQueryFlat <$> V.runValidate (runFromIr deleteQuery) `onLeft` (throw500 . tshow)
-- Execute DELETE statement
Tx.unitQueryE fromMSSQLTxError deleteQueryValidated
mutationOutputSelect <- mkMutationOutputSelect stringifyNum withAlias $ dqp1Output deleteOperation
let withSelect =
emptySelect
{ selectProjections = [StarProjection],
selectFrom = Just $ FromTempTable $ Aliased tempTableNameDeleted "deleted_alias"
}
finalMutationOutputSelect = mutationOutputSelect {selectWith = Just $ With $ pure $ Aliased withSelect withAlias}
mutationOutputSelectQuery = toQueryFlat $ TQ.fromSelect finalMutationOutputSelect
-- Execute SELECT query and fetch mutation response
encJFromText <$> Tx.singleRowQueryE fromMSSQLTxError mutationOutputSelectQuery
-- | Generate a SQL SELECT statement which outputs the mutation response
--
-- For multi row inserts:
-- SELECT (SELECT COUNT(*) FROM [with_alias]) AS [affected_rows], (select_from_returning) AS [returning] FOR JSON PATH, INCLUDE_NULL_VALUES, WITHOUT_ARRAY_WRAPPER
--
-- For single row insert: the selection set is translated to SQL query using @'mkSQLSelect'
mkMutationOutputSelect ::
(MonadError QErr m) =>
Bool ->
Text ->
MutationOutputG 'MSSQL (Const Void) Expression ->
m Select
mkMutationOutputSelect stringifyNum withAlias = \case
IR.MOutMultirowFields multiRowFields -> do
projections <- forM multiRowFields $ \(fieldName, field') -> do
let mkProjection = ExpressionProjection . flip Aliased (getFieldNameTxt fieldName) . SelectExpression
mkProjection <$> case field' of
IR.MCount -> pure $ countSelect withAlias
IR.MExp t -> pure $ textSelect t
IR.MRet returningFields -> mkSelect stringifyNum withAlias JASMultipleRows returningFields
let forJson = JsonFor $ ForJson JsonSingleton NoRoot
pure emptySelect {selectFor = forJson, selectProjections = projections}
IR.MOutSinglerowObject singleRowField -> mkSelect stringifyNum withAlias JASSingleObject singleRowField
mkSelect ::
MonadError QErr m =>
Bool ->
Text ->
JsonAggSelect ->
Fields (AnnFieldG 'MSSQL (Const Void) Expression) ->
m Select
mkSelect stringifyNum withAlias jsonAggSelect annFields = do
let annSelect = IR.AnnSelectG annFields (IR.FromIdentifier withAlias) IR.noTablePermissions IR.noSelectArgs stringifyNum
V.runValidate (runFromIr $ mkSQLSelect jsonAggSelect annSelect) `onLeft` (throw500 . tshow)
-- SELECT COUNT(*) AS "count" FROM [with_alias]
countSelect :: Text -> Select
countSelect withAlias =
let countProjection = AggregateProjection $ Aliased (CountAggregate StarCountable) "count"
in emptySelect
{ selectProjections = [countProjection],
selectFrom = Just $ TSQL.FromIdentifier withAlias
}
-- SELECT '<text-value>' AS "exp"
textSelect :: Text -> Select
textSelect t =
let textProjection = ExpressionProjection $ Aliased (ValueExpression (ODBC.TextValue t)) "exp"
in emptySelect {selectProjections = [textProjection]}
-- subscription
msDBSubscriptionPlan ::
forall m.
( MonadError QErr m,
MonadIO m,
MonadBaseControl IO m
) =>
UserInfo ->
SourceName ->
SourceConfig 'MSSQL ->
Maybe G.Name ->
RootFieldMap (QueryDB 'MSSQL (Const Void) (UnpreparedValue 'MSSQL)) ->
m (LiveQueryPlan 'MSSQL (MultiplexedQuery 'MSSQL))
msDBSubscriptionPlan UserInfo {_uiSession, _uiRole} _sourceName sourceConfig namespace rootFields = do
(reselect, prepareState) <- planSubscription (OMap.mapKeys _rfaAlias rootFields) _uiSession
cohortVariables <- prepareStateCohortVariables sourceConfig _uiSession prepareState
let parameterizedPlan = ParameterizedLiveQueryPlan _uiRole $ MultiplexedQuery' reselect
pure $
LiveQueryPlan parameterizedPlan sourceConfig cohortVariables namespace
prepareStateCohortVariables :: (MonadError QErr m, MonadIO m, MonadBaseControl IO m) => SourceConfig 'MSSQL -> SessionVariables -> PrepareState -> m CohortVariables
prepareStateCohortVariables sourceConfig session prepState = do
(namedVars, posVars) <- validateVariables sourceConfig session prepState
let PrepareState {sessionVariables} = prepState
pure $
mkCohortVariables
sessionVariables
session
namedVars
posVars
-- | Ensure that the set of variables (with value instantiations) that occur in
-- a (RQL) query produce a well-formed and executable (SQL) query when
-- considered in isolation.
--
-- This helps avoiding cascading failures in multiplexed queries.
--
-- c.f. https://github.com/hasura/graphql-engine-mono/issues/1210.
validateVariables ::
(MonadError QErr m, MonadIO m, MonadBaseControl IO m) =>
SourceConfig 'MSSQL ->
SessionVariables ->
PrepareState ->
m (ValidatedQueryVariables, ValidatedSyntheticVariables)
validateVariables sourceConfig sessionVariableValues prepState = do
let PrepareState {sessionVariables, namedArguments, positionalArguments} = prepState
-- We generate a single 'canary' query in the form:
--
-- SELECT ... [session].[x-hasura-foo] as [x-hasura-foo], ... as a, ... as b, ...
-- FROM OPENJSON('...')
-- WITH ([x-hasura-foo] NVARCHAR(MAX)) as [session]
--
-- where 'a', 'b', etc. are aliases given to positional arguments.
-- Named arguments and session variables are aliased to themselves.
--
-- The idea being that if the canary query succeeds we can be
-- reasonably confident that adding these variables to a query being
-- polled will not crash the poller.
occSessionVars =
filterSessionVariables
(\k _ -> Set.member k sessionVariables)
sessionVariableValues
expSes, expNamed, expPos :: [Aliased Expression]
expSes = sessionReference <$> getSessionVariables occSessionVars
expNamed =
map
( \(n, v) -> Aliased (ValueExpression (RQLColumn.cvValue v)) (G.unName n)
)
$ Map.toList $ namedArguments
-- For positional args we need to be a bit careful not to capture names
-- from expNamed and expSes (however unlikely)
expPos =
zipWith
(\n v -> Aliased (ValueExpression (RQLColumn.cvValue v)) n)
(freshVars (expNamed <> expSes))
positionalArguments
projAll :: [Projection]
projAll = map ExpressionProjection (expSes <> expNamed <> expPos)
canaryQuery =
if null projAll
then Nothing
else
Just $
renderQuery
emptySelect
{ selectProjections = projAll,
selectFrom = sessionOpenJson occSessionVars
}
onJust
canaryQuery
( \q -> do
_ :: [[ODBC.Value]] <- withMSSQLPool (_mscConnectionPool sourceConfig) (`ODBC.query` q)
pure ()
)
pure
( ValidatedVariables $ txtEncodedColVal <$> namedArguments,
ValidatedVariables $ txtEncodedColVal <$> positionalArguments
)
where
renderQuery :: Select -> ODBC.Query
renderQuery = toQueryFlat . fromSelect
freshVars :: [Aliased a] -> [Text]
freshVars boundNames = filter (not . (`elem` map aliasedAlias boundNames)) chars
-- Infinite list of expression aliases.
chars :: [Text]
chars = [y T.<>> x | y <- [""] <|> chars, x <- ['a' .. 'z']]
sessionOpenJson :: SessionVariables -> Maybe From
sessionOpenJson occSessionVars =
nonEmpty (getSessionVariables occSessionVars)
<&> \fields ->
FromOpenJson $
Aliased
( OpenJson
(ValueExpression $ ODBC.TextValue $ lbsToTxt $ J.encode occSessionVars)
(pure (sessField <$> fields))
)
"session"
sessField :: Text -> JsonFieldSpec
sessField var = StringField var Nothing
sessionReference :: Text -> Aliased Expression
sessionReference var = Aliased (ColumnExpression (TSQL.FieldName var "session")) var
--------------------------------------------------------------------------------
-- Remote Relationships (e.g. DB-to-DB Joins, remote schema joins, etc.)
--------------------------------------------------------------------------------
-- | Construct an action (i.e. 'DBStepInfo') which can marshal some remote
-- relationship information into a form that SQL Server can query against.
--
-- XXX: Currently unimplemented; the Postgres implementation uses
-- @jsonb_to_recordset@ to query the remote relationship, however this
-- functionality doesn't exist in SQL Server.
--
-- NOTE: The following typeclass constraints will be necessary when implementing
-- this function for real:
--
-- @
-- MonadQueryTags m
-- Backend 'MSSQL
-- @
msDBRemoteRelationshipPlan ::
forall m.
( MonadError QErr m
) =>
UserInfo ->
SourceName ->
SourceConfig 'MSSQL ->
-- | List of json objects, each of which becomes a row of the table.
NonEmpty J.Object ->
-- | The above objects have this schema
--
-- XXX: What is this for/what does this mean?
HashMap RQLTypes.FieldName (RQLTypes.Column 'MSSQL, RQLTypes.ScalarType 'MSSQL) ->
-- | This is a field name from the lhs that *has* to be selected in the
-- response along with the relationship.
RQLTypes.FieldName ->
(RQLTypes.FieldName, SourceRelationshipSelection 'MSSQL (Const Void) UnpreparedValue) ->
m (DBStepInfo 'MSSQL)
msDBRemoteRelationshipPlan _userInfo _sourceName _sourceConfig _lhs _lhsSchema _argumentId _relationship = do
throw500 "mkDBRemoteRelationshipPlan: SQL Server (MSSQL) does not currently support generalized joins."