{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE QuasiQuotes #-}
{-# LANGUAGE TemplateHaskell #-}
{-# OPTIONS_GHC -Wno-orphans #-}
module Postgres.MonadPostgres where
import AtLeast (AtLeast)
import Control.Exception
import Control.Monad.Except
import Control.Monad.Logger (MonadLogger, logDebug, logWarn)
import Control.Monad.Reader (MonadReader (ask), ReaderT (..))
import Control.Monad.Trans.Resource
import Data.Aeson (FromJSON)
import Data.Error.Tree
import Data.Int (Int64)
import Data.Kind (Type)
import Data.List qualified as List
import Data.Pool (Pool)
import Data.Pool qualified as Pool
import Data.Text qualified as Text
import Data.Typeable (Typeable)
import Database.PostgreSQL.Simple (Connection, FormatError, FromRow, Query, QueryError, ResultError, SqlError, ToRow)
import Database.PostgreSQL.Simple qualified as PG
import Database.PostgreSQL.Simple qualified as Postgres
import Database.PostgreSQL.Simple.FromRow qualified as PG
import Database.PostgreSQL.Simple.ToField (ToField)
import Database.PostgreSQL.Simple.ToRow (ToRow (toRow))
import Database.PostgreSQL.Simple.Types (Query (..))
import GHC.Records (HasField (..))
import Label
import PossehlAnalyticsPrelude
import Postgres.Decoder
import Postgres.Decoder qualified as Dec
import Pretty (showPretty)
import Seconds
import System.Exit (ExitCode (..))
import Tool
import UnliftIO (MonadUnliftIO (withRunInIO))
import UnliftIO.Process qualified as Process
import UnliftIO.Resource qualified as Resource
-- | Postgres queries/commands that can be executed within a running transaction.
--
-- These are implemented with the @postgresql-simple@ primitives of the same name
-- and will behave the same unless othewise documented.
class Monad m => MonadPostgres (m :: Type -> Type) where
-- | Execute an INSERT, UPDATE, or other SQL query that is not expected to return results.
-- Returns the number of rows affected.
execute :: (ToRow params, Typeable params) => Query -> params -> Transaction m (Label "numberOfRowsAffected" Natural)
-- | Execute an INSERT, UPDATE, or other SQL query that is not expected to return results. Does not take parameters.
-- Returns the number of rows affected.
execute_ :: Query -> Transaction m (Label "numberOfRowsAffected" Natural)
-- | Execute a multi-row INSERT, UPDATE, or other SQL query that is not expected to return results.
--
-- Returns the number of rows affected. If the list of parameters is empty, this function will simply return 0 without issuing the query to the backend. If this is not desired, consider using the 'PG.Values' constructor instead.
executeMany :: (ToRow params, Typeable params) => Query -> [params] -> Transaction m (Label "numberOfRowsAffected" Natural)
-- | Execute INSERT ... RETURNING, UPDATE ... RETURNING, or other SQL query that accepts multi-row input and is expected to return results. Note that it is possible to write query conn "INSERT ... RETURNING ..." ... in cases where you are only inserting a single row, and do not need functionality analogous to 'executeMany'.
--
-- If the list of parameters is empty, this function will simply return [] without issuing the query to the backend. If this is not desired, consider using the 'PG.Values' constructor instead.
executeManyReturningWith :: (ToRow q) => Query -> [q] -> Decoder r -> Transaction m [r]
-- | Run a query, passing parameters and result row parser.
queryWith :: (PG.ToRow params, Typeable params, Typeable r) => PG.Query -> params -> Decoder r -> Transaction m [r]
-- | Run a query without any parameters and result row parser.
queryWith_ :: (Typeable r) => PG.Query -> Decoder r -> Transaction m [r]
-- | Run a query, passing parameters, and fold over the resulting rows.
--
-- This doesn’t have to realize the full list of results in memory,
-- rather results are streamed incrementally from the database.
--
-- When dealing with small results, it may be simpler (and perhaps faster) to use query instead.
--
-- This fold is _not_ strict. The stream consumer is responsible for forcing the evaluation of its result to avoid space leaks.
--
-- If you can, prefer aggregating in the database itself.
foldRows ::
(FromRow row, ToRow params, Typeable row, Typeable params) =>
Query ->
params ->
a ->
(a -> row -> Transaction m a) ->
Transaction m a
-- | Run a given transaction in a transaction block, rolling back the transaction
-- if any exception (postgres or Haskell Exception) is thrown during execution.
--
-- Re-throws the exception.
--
-- Don’t do any long-running things on the Haskell side during a transaction,
-- because it will block a database connection and potentially also lock
-- database tables from being written or read by other clients.
--
-- Nonetheless, try to push transactions as far out to the handlers as possible,
-- don’t do something like @runTransaction $ query …@, because it will lead people
-- to accidentally start nested transactions (the inner transaction is run on a new connections,
-- thus can’t see any changes done by the outer transaction).
-- Only handlers should run transactions.
runTransaction :: Transaction m a -> m a
-- | Run a query, passing parameters.
query :: forall m params r. (PG.ToRow params, PG.FromRow r, Typeable params, Typeable r, MonadPostgres m) => PG.Query -> params -> Transaction m [r]
query qry params = queryWith qry params (Decoder PG.fromRow)
-- | Run a query without any parameters.
query_ :: forall m r. (Typeable r, PG.FromRow r, MonadPostgres m) => PG.Query -> Transaction m [r]
query_ qry = queryWith_ qry (Decoder PG.fromRow)
-- TODO: implement via fold, so that the result doesn’t have to be realized in memory
querySingleRow ::
( MonadPostgres m,
ToRow qParams,
Typeable qParams,
FromRow a,
Typeable a,
MonadThrow m
) =>
Query ->
qParams ->
Transaction m a
querySingleRow qry params = do
query qry params >>= ensureSingleRow
-- TODO: implement via fold, so that the result doesn’t have to be realized in memory
querySingleRowMaybe ::
( MonadPostgres m,
ToRow qParams,
Typeable qParams,
FromRow a,
Typeable a,
MonadThrow m
) =>
Query ->
qParams ->
Transaction m (Maybe a)
querySingleRowMaybe qry params = do
rows <- query qry params
case rows of
[] -> pure Nothing
[one] -> pure (Just one)
-- TODO: Should we MonadThrow this here? It’s really an implementation detail of MonadPostgres
-- that a database function can error out, should probably handled by the instances.
more -> throwM $ SingleRowError {numberOfRowsReturned = (List.length more)}
ensureSingleRow :: MonadThrow m => [a] -> m a
ensureSingleRow = \case
-- TODO: Should we MonadThrow this here? It’s really an implementation detail of MonadPostgres
-- that a database function can error out, should probably handled by the instances.
[] -> throwM (SingleRowError {numberOfRowsReturned = 0})
[one] -> pure one
more ->
throwM $
SingleRowError
{ numberOfRowsReturned =
-- TODO: this is VERY bad, because it requires to parse the full database output, even if there’s 10000000000 elements
List.length more
}
newtype Transaction m a = Transaction {unTransaction :: (ReaderT Connection m a)}
deriving newtype
( Functor,
Applicative,
Monad,
MonadThrow,
MonadLogger,
MonadIO,
MonadUnliftIO,
MonadTrans
)
runTransaction' :: Connection -> Transaction m a -> m a
runTransaction' conn transaction = runReaderT transaction.unTransaction conn
-- | [Resource Pool](http://hackage.haskell.org/package/resource-pool-0.2.3.2/docs/Data-Pool.html) configuration.
data PoolingInfo = PoolingInfo
{ -- | Minimal amount of resources that are
-- always available.
numberOfStripes :: AtLeast 1 Int,
-- | Time after which extra resources
-- (above minimum) can stay in the pool
-- without being used.
unusedResourceOpenTime :: Seconds,
-- | Max number of resources that can be
-- in the Pool at any time
maxOpenResourcesPerStripe :: AtLeast 1 Int
}
deriving stock (Generic, Eq, Show)
deriving anyclass (FromJSON)
initMonadPostgres ::
(Text -> IO ()) ->
-- | Info describing the connection to the Postgres DB
Postgres.ConnectInfo ->
-- | Configuration info for pooling attributes
PoolingInfo ->
-- | Created Postgres connection pool
ResourceT IO (Pool Postgres.Connection)
initMonadPostgres logInfoFn connectInfo poolingInfo = do
(_releaseKey, connPool) <-
Resource.allocate
(logInfoFn "Creating Postgres Connection Pool" >> createPGConnPool)
(\pool -> logInfoFn "Destroying Postgres Connection Pool" >> destroyPGConnPool pool)
pure connPool
where
-- \| Create a Postgres connection pool
createPGConnPool ::
IO (Pool Postgres.Connection)
createPGConnPool =
Pool.createPool
poolCreateResource
poolfreeResource
poolingInfo.numberOfStripes.unAtLeast
(poolingInfo.unusedResourceOpenTime & secondsToNominalDiffTime)
(poolingInfo.maxOpenResourcesPerStripe.unAtLeast)
where
poolCreateResource = Postgres.connect connectInfo
poolfreeResource = Postgres.close
-- \| Destroy a Postgres connection pool
destroyPGConnPool ::
-- \| Pool to be destroyed
(Pool Postgres.Connection) ->
IO ()
destroyPGConnPool p = Pool.destroyAllResources p
-- | Catch any Postgres exception that gets thrown,
-- print the query that was run and the query parameters,
-- then rethrow inside an 'Error'.
handlePGException ::
forall a params tools m.
(ToRow params, MonadUnliftIO m, MonadLogger m, HasField "pgFormat" tools Tool) =>
tools ->
Text ->
Query ->
-- | Depending on whether we used `format` or `formatMany`.
Either params [params] ->
IO a ->
Transaction m a
handlePGException tools queryType query' params io = do
withRunInIO $ \unliftIO ->
io
`catches` [ Handler $ unliftIO . logQueryException @SqlError,
Handler $ unliftIO . logQueryException @QueryError,
Handler $ unliftIO . logQueryException @ResultError,
Handler $ unliftIO . logFormatException
]
where
-- TODO: use throwInternalError here (after pulling it into the MonadPostgres class)
throwAsError = unwrapIOError . Left . newError
throwErr err = liftIO $ throwAsError $ prettyErrorTree $ nestedMultiError "A Postgres query failed" err
logQueryException :: Exception e => e -> Transaction m a
logQueryException exc = do
formattedQuery <- case params of
Left one -> pgFormatQuery' tools query' one
Right many -> pgFormatQueryMany' tools query' many
throwErr
( singleError [fmt|Query Type: {queryType}|]
:| [ nestedError "Exception" (exc & showPretty & newError & singleError),
nestedError "Query" (formattedQuery & newError & singleError)
]
)
logFormatException :: FormatError -> Transaction m a
logFormatException fe = throwErr (fe & showPretty & newError & singleError & singleton)
-- | Perform a Postgres action within a transaction
withPGTransaction ::
-- | Postgres connection pool to be used for the action
(Pool Postgres.Connection) ->
-- | DB-action to be performed
(Postgres.Connection -> IO a) ->
-- | Result of the DB-action
IO a
withPGTransaction connPool f =
Pool.withResource
connPool
(\conn -> Postgres.withTransaction conn (f conn))
runPGTransactionImpl :: MonadUnliftIO m => m (Pool Postgres.Connection) -> Transaction m a -> m a
{-# INLINE runPGTransactionImpl #-}
runPGTransactionImpl zoom (Transaction transaction) = do
pool <- zoom
withRunInIO $ \unliftIO ->
withPGTransaction pool $ \conn -> do
unliftIO $ runReaderT transaction conn
executeImpl ::
(ToRow params, MonadUnliftIO m, MonadLogger m, HasField "pgFormat" tools Tool) =>
m tools ->
m DebugLogDatabaseQueries ->
Query ->
params ->
Transaction m (Label "numberOfRowsAffected" Natural)
{-# INLINE executeImpl #-}
executeImpl zoomTools zoomDebugLogDatabaseQueries qry params = do
tools <- lift @Transaction zoomTools
logDatabaseQueries <- lift @Transaction zoomDebugLogDatabaseQueries
logQueryIfEnabled tools logDatabaseQueries qry (HasSingleParam params)
conn <- Transaction ask
PG.execute conn qry params
& handlePGException tools "execute" qry (Left params)
>>= toNumberOfRowsAffected "executeImpl"
executeImpl_ ::
(MonadUnliftIO m, MonadLogger m, HasField "pgFormat" tools Tool) =>
m tools ->
m DebugLogDatabaseQueries ->
Query ->
Transaction m (Label "numberOfRowsAffected" Natural)
{-# INLINE executeImpl_ #-}
executeImpl_ zoomTools zoomDebugLogDatabaseQueries qry = do
tools <- lift @Transaction zoomTools
logDatabaseQueries <- lift @Transaction zoomDebugLogDatabaseQueries
logQueryIfEnabled @() tools logDatabaseQueries qry HasNoParams
conn <- Transaction ask
PG.execute_ conn qry
& handlePGException tools "execute_" qry (Left ())
>>= toNumberOfRowsAffected "executeImpl_"
executeManyImpl ::
(ToRow params, MonadUnliftIO m, MonadLogger m, HasField "pgFormat" tools Tool) =>
m tools ->
m DebugLogDatabaseQueries ->
Query ->
[params] ->
Transaction m (Label "numberOfRowsAffected" Natural)
executeManyImpl zoomTools zoomDebugLogDatabaseQueries qry params = do
tools <- lift @Transaction zoomTools
logDatabaseQueries <- lift @Transaction zoomDebugLogDatabaseQueries
logQueryIfEnabled tools logDatabaseQueries qry (HasMultiParams params)
conn <- Transaction ask
PG.executeMany conn qry params
& handlePGException tools "executeMany" qry (Right params)
>>= toNumberOfRowsAffected "executeManyImpl"
toNumberOfRowsAffected :: MonadIO m => Text -> Int64 -> m (Label "numberOfRowsAffected" Natural)
toNumberOfRowsAffected functionName i64 =
i64
& intToNatural
& annotate [fmt|{functionName}: postgres returned a negative number of rows affected: {i64}|]
-- we throw this directly in IO here, because we don’t want to e.g. have to propagate MonadThrow through user code (it’s an assertion)
& unwrapIOError
& liftIO
<&> label @"numberOfRowsAffected"
executeManyReturningWithImpl ::
(ToRow params, MonadUnliftIO m, MonadLogger m, HasField "pgFormat" tools Tool) =>
m tools ->
m DebugLogDatabaseQueries ->
Query ->
[params] ->
Decoder r ->
Transaction m [r]
{-# INLINE executeManyReturningWithImpl #-}
executeManyReturningWithImpl zoomTools zoomDebugLogDatabaseQueries qry params (Decoder fromRow) = do
tools <- lift @Transaction zoomTools
logDatabaseQueries <- lift @Transaction zoomDebugLogDatabaseQueries
logQueryIfEnabled tools logDatabaseQueries qry (HasMultiParams params)
conn <- Transaction ask
PG.returningWith fromRow conn qry params
& handlePGException tools "executeManyReturning" qry (Right params)
foldRowsImpl ::
(FromRow row, ToRow params, MonadUnliftIO m, MonadLogger m, HasField "pgFormat" tools Tool) =>
m tools ->
Query ->
params ->
a ->
(a -> row -> Transaction m a) ->
Transaction m a
{-# INLINE foldRowsImpl #-}
foldRowsImpl zoomTools qry params accumulator f = do
conn <- Transaction ask
tools <- lift @Transaction zoomTools
withRunInIO
( \runInIO ->
do
PG.fold
conn
qry
params
accumulator
(\acc row -> runInIO $ f acc row)
& handlePGException tools "fold" qry (Left params)
& runInIO
)
pgFormatQueryNoParams' ::
(MonadIO m, MonadLogger m, HasField "pgFormat" tools Tool) =>
tools ->
Query ->
Transaction m Text
pgFormatQueryNoParams' tools q =
lift $ pgFormatQueryByteString tools q.fromQuery
pgFormatQuery :: (ToRow params, MonadIO m) => Query -> params -> Transaction m ByteString
pgFormatQuery qry params = Transaction $ do
conn <- ask
liftIO $ PG.formatQuery conn qry params
pgFormatQueryMany :: (MonadIO m, ToRow params) => Query -> [params] -> Transaction m ByteString
pgFormatQueryMany qry params = Transaction $ do
conn <- ask
liftIO $ PG.formatMany conn qry params
queryWithImpl ::
(ToRow params, MonadUnliftIO m, MonadLogger m, HasField "pgFormat" tools Tool) =>
m tools ->
m DebugLogDatabaseQueries ->
Query ->
params ->
Decoder r ->
Transaction m [r]
{-# INLINE queryWithImpl #-}
queryWithImpl zoomTools zoomDebugLogDatabaseQueries qry params (Decoder fromRow) = do
tools <- lift @Transaction zoomTools
logDatabaseQueries <- lift @Transaction zoomDebugLogDatabaseQueries
logQueryIfEnabled tools logDatabaseQueries qry (HasSingleParam params)
conn <- Transaction ask
PG.queryWith fromRow conn qry params
& handlePGException tools "query" qry (Left params)
queryWithImpl_ :: (MonadUnliftIO m, MonadLogger m, HasField "pgFormat" tools Tool) => m tools -> Query -> Decoder r -> Transaction m [r]
{-# INLINE queryWithImpl_ #-}
queryWithImpl_ zoomTools qry (Decoder fromRow) = do
tools <- lift @Transaction zoomTools
conn <- Transaction ask
liftIO (PG.queryWith_ fromRow conn qry)
& handlePGException tools "query" qry (Left ())
pgQuery :: (ToRow params, FromRow r, MonadUnliftIO m, MonadLogger m, HasField "pgFormat" tools Tool) => tools -> Query -> params -> Transaction m [r]
pgQuery tools qry params = do
conn <- Transaction ask
PG.query conn qry params
& handlePGException tools "query" qry (Left params)
pgQuery_ :: (FromRow r, MonadUnliftIO m, MonadLogger m, HasField "pgFormat" tools Tool) => tools -> Query -> Transaction m [r]
pgQuery_ tools qry = do
conn <- Transaction ask
PG.query_ conn qry
& handlePGException tools "query_" qry (Left ())
data SingleRowError = SingleRowError
{ -- | How many columns were actually returned by the query
numberOfRowsReturned :: Int
}
deriving stock (Show)
instance Exception SingleRowError where
displayException (SingleRowError {..}) = [fmt|Single row expected from SQL query result, {numberOfRowsReturned} rows were returned instead."|]
pgFormatQuery' :: (MonadIO m, ToRow params, MonadLogger m, HasField "pgFormat" tools Tool) => tools -> Query -> params -> Transaction m Text
pgFormatQuery' tools q p =
pgFormatQuery q p
>>= lift . pgFormatQueryByteString tools
pgFormatQueryMany' :: (MonadIO m, ToRow params, MonadLogger m, HasField "pgFormat" tools Tool) => tools -> Query -> [params] -> Transaction m Text
pgFormatQueryMany' tools q p =
pgFormatQueryMany q p
>>= lift . pgFormatQueryByteString tools
-- | Read the executable name "pg_format"
postgresToolsParser :: ToolParserT IO (Label "pgFormat" Tool)
postgresToolsParser = label @"pgFormat" <$> readTool "pg_format"
pgFormatQueryByteString :: (MonadIO m, MonadLogger m, HasField "pgFormat" tools Tool) => tools -> ByteString -> m Text
pgFormatQueryByteString tools queryBytes = do
do
(exitCode, stdout, stderr) <-
Process.readProcessWithExitCode
tools.pgFormat.toolPath
["-"]
(queryBytes & bytesToTextUtf8Lenient & textToString)
case exitCode of
ExitSuccess -> pure (stdout & stringToText)
ExitFailure status -> do
$logWarn [fmt|pg_format failed with status {status} while formatting the query, using original query string. Is there a syntax error?|]
$logDebug
( prettyErrorTree
( nestedMultiError
"pg_format output"
( nestedError "stdout" (singleError (stdout & stringToText & newError))
:| [(nestedError "stderr" (singleError (stderr & stringToText & newError)))]
)
)
)
$logDebug [fmt|pg_format stdout: stderr|]
pure (queryBytes & bytesToTextUtf8Lenient)
data DebugLogDatabaseQueries
= -- | Do not log the database queries
DontLogDatabaseQueries
| -- | Log the database queries as debug output;
LogDatabaseQueries
| -- | Log the database queries as debug output and additionally the EXPLAIN output (from the query analyzer, not the actual values after execution cause that’s a bit harder to do)
LogDatabaseQueriesAndExplain
deriving stock (Show, Enum, Bounded)
data HasQueryParams param
= HasNoParams
| HasSingleParam param
| HasMultiParams [param]
-- | Log the postgres query depending on the given setting
logQueryIfEnabled ::
( ToRow params,
MonadUnliftIO m,
MonadLogger m,
HasField "pgFormat" tools Tool
) =>
tools ->
DebugLogDatabaseQueries ->
Query ->
HasQueryParams params ->
Transaction m ()
logQueryIfEnabled tools logDatabaseQueries qry params = do
-- In case we have query logging enabled, we want to do that
let formattedQuery = case params of
HasNoParams -> pgFormatQueryNoParams' tools qry
HasSingleParam p -> pgFormatQuery' tools qry p
HasMultiParams ps -> pgFormatQueryMany' tools qry ps
let doLog errs =
errs
& nestedMultiError "Postgres query"
& prettyErrorTree
& $logDebug
& lift
let addQuery = do
formattedQuery
<&> newError
<&> singleError
let addExplain = do
q <- formattedQuery
queryWithImpl_
(pure tools)
( "EXPLAIN "
<> (
-- TODO: this is not nice, but the only way to get the `executeMany` form to work with this
-- because we need the query with all elements already interpolated.
Query (q & textToBytesUtf8)
)
)
(Dec.fromField @Text)
<&> Text.intercalate "\n"
<&> newError
<&> singleError
case logDatabaseQueries of
DontLogDatabaseQueries -> pure ()
LogDatabaseQueries -> do
aq <- addQuery
doLog (aq :| [])
LogDatabaseQueriesAndExplain -> do
aq <- addQuery
-- XXX: stuff like `CREATE SCHEMA` cannot be EXPLAINed, so we should catch exceptions here
-- and just ignore anything that errors (if it errors because of a problem with the query, it would have been caught by the query itself.
ex <- addExplain
doLog (nestedError "Query" aq :| [nestedError "Explain" ex])
instance (ToField t1) => ToRow (Label l1 t1) where
toRow t2 = toRow $ PG.Only $ getField @l1 t2
instance (ToField t1, ToField t2) => ToRow (T2 l1 t1 l2 t2) where
toRow t2 = toRow (getField @l1 t2, getField @l2 t2)
instance (ToField t1, ToField t2, ToField t3) => ToRow (T3 l1 t1 l2 t2 l3 t3) where
toRow t3 = toRow (getField @l1 t3, getField @l2 t3, getField @l3 t3)
