postgresql-simple-0.0: src/Database/PostgreSQL/Simple.hs
{-# LANGUAGE BangPatterns, DeriveDataTypeable, OverloadedStrings #-}
{-# LANGUAGE DoAndIfThenElse, RecordWildCards, NamedFieldPuns #-}
------------------------------------------------------------------------------
-- |
-- Module: Database.PostgreSQL.Simple
-- Copyright: (c) 2011 MailRank, Inc.
-- (c) 2011 Leon P Smith
-- License: BSD3
-- Maintainer: Leon P Smith <leon@melding-monads.com>
-- Stability: experimental
-- Portability: portable
--
-- A mid-level client library for the PostgreSQL database, aimed at ease of
-- use and high performance.
--
------------------------------------------------------------------------------
module Database.PostgreSQL.Simple
(
-- * Writing queries
-- $use
-- ** The Query type
-- $querytype
-- ** Parameter substitution
-- $subst
-- *** Type inference
-- $inference
-- ** Substituting a single parameter
-- $only_param
-- ** Representing a list of values
-- $in
-- ** Modifying multiple rows at once
-- $many
-- * Extracting results
-- $result
-- ** Handling null values
-- $null
-- ** Type conversions
-- $types
-- * Types
Base.ConnectInfo(..)
, Connection
, Query
, In(..)
, Binary(..)
, Only(..)
-- ** Exceptions
, FormatError(fmtMessage, fmtQuery, fmtParams)
, QueryError(qeMessage, qeQuery)
, ResultError(errSQLType, errHaskellType, errMessage)
-- * Connection management
, Base.connect
, Base.connectPostgreSQL
, Base.postgreSQLConnectionString
, Base.defaultConnectInfo
, Base.close
-- * Queries that return results
, query
, query_
{--
-- * Queries that stream results
, fold
, fold_
, forEach
, forEach_
--}
-- * Statements that do not return results
, execute
, execute_
, executeMany
-- , Base.insertID
-- * Transaction handling
, withTransaction
-- , Base.autocommit
, begin
, commit
, rollback
-- * Helper functions
, formatMany
, formatQuery
) where
import Blaze.ByteString.Builder (Builder, fromByteString, toByteString)
import Blaze.ByteString.Builder.Char8 (fromChar)
import Control.Applicative ((<$>), pure)
import Control.Concurrent.MVar
import Control.Exception (Exception, bracket, onException, throw, throwIO)
import Control.Monad (forM)
import Control.Monad.Fix (fix)
import Data.ByteString (ByteString)
-- import qualified Data.ByteString as B (unpack)
import Data.Char(ord)
import Data.Int (Int64)
import qualified Data.IntMap as IntMap
import Data.List (intersperse)
import Data.Monoid (mappend, mconcat)
import Data.Typeable (Typeable)
--import Database.MySQL.Base (Connection, Result)
--import Database.MySQL.Base.Types (Field)
import Database.PostgreSQL.Simple.BuiltinTypes (oid2builtin, builtin2typname)
import Database.PostgreSQL.Simple.Param (Action(..), inQuotes)
import Database.PostgreSQL.Simple.QueryParams (QueryParams(..))
import Database.PostgreSQL.Simple.Result (ResultError(..))
import Database.PostgreSQL.Simple.QueryResults (QueryResults(..))
-- import Database.PostgreSQL.Simple.Result (ResultError(..))
import Database.PostgreSQL.Simple.Types (Binary(..), In(..), Only(..), Query(..))
import Database.PostgreSQL.Simple.Internal as Base
import qualified Database.PostgreSQL.LibPQ as PQ
import Text.Regex.PCRE.Light (compile, caseless, match)
import qualified Data.ByteString.Char8 as B
--import qualified Database.MySQL.Base as Base
-- | Exception thrown if a 'Query' could not be formatted correctly.
-- This may occur if the number of \'@?@\' characters in the query
-- string does not match the number of parameters provided.
data FormatError = FormatError {
fmtMessage :: String
, fmtQuery :: Query
, fmtParams :: [ByteString]
} deriving (Eq, Show, Typeable)
instance Exception FormatError
-- | Exception thrown if 'query' is used to perform an @INSERT@-like
-- operation, or 'execute' is used to perform a @SELECT@-like operation.
data QueryError = QueryError {
qeMessage :: String
, qeQuery :: Query
} deriving (Eq, Show, Typeable)
instance Exception QueryError
-- | Format a query string.
--
-- This function is exposed to help with debugging and logging. Do not
-- use it to prepare queries for execution.
--
-- String parameters are escaped according to the character set in use
-- on the 'Connection'.
--
-- Throws 'FormatError' if the query string could not be formatted
-- correctly.
formatQuery :: QueryParams q => Connection -> Query -> q -> IO ByteString
formatQuery conn q@(Query template) qs
| null xs && '?' `B.notElem` template = return template
| otherwise = toByteString <$> buildQuery conn q template xs
where xs = renderParams qs
-- | Format a query string with a variable number of rows.
--
-- This function is exposed to help with debugging and logging. Do not
-- use it to prepare queries for execution.
--
-- The query string must contain exactly one substitution group,
-- identified by the SQL keyword \"@VALUES@\" (case insensitive)
-- followed by an \"@(@\" character, a series of one or more \"@?@\"
-- characters separated by commas, and a \"@)@\" character. White
-- space in a substitution group is permitted.
--
-- Throws 'FormatError' if the query string could not be formatted
-- correctly.
formatMany :: (QueryParams q) => Connection -> Query -> [q] -> IO ByteString
formatMany _ q [] = fmtError "no rows supplied" q []
formatMany conn q@(Query template) qs = do
case match re template [] of
Just [_,before,qbits,after] -> do
bs <- mapM (buildQuery conn q qbits . renderParams) qs
return . toByteString . mconcat $ fromByteString before :
intersperse (fromChar ',') bs ++
[fromByteString after]
_ -> error "foo"
where
re = compile "^([^?]+\\bvalues\\s*)\
\(\\(\\s*[?](?:\\s*,\\s*[?])*\\s*\\))\
\([^?]*)$"
[caseless]
escapeStringConn conn s = withConnection conn $ \c -> do
PQ.escapeStringConn c s
buildQuery :: Connection -> Query -> ByteString -> [Action] -> IO Builder
buildQuery conn q template xs = zipParams (split template) <$> mapM sub xs
where quote = inQuotes . fromByteString . maybe undefined id
sub (Plain b) = pure b
sub (Escape s) = quote <$> escapeStringConn conn s
sub (Many ys) = mconcat <$> mapM sub ys
split s = fromByteString h : if B.null t then [] else split (B.tail t)
where (h,t) = B.break (=='?') s
zipParams (t:ts) (p:ps) = t `mappend` p `mappend` zipParams ts ps
zipParams [t] [] = t
zipParams _ _ = fmtError (show (B.count '?' template) ++
" '?' characters, but " ++
show (length xs) ++ " parameters") q xs
-- | Execute an @INSERT@, @UPDATE@, or other SQL query that is not
-- expected to return results.
--
-- Returns the number of rows affected.
--
-- Throws 'FormatError' if the query could not be formatted correctly.
execute :: (QueryParams q) => Connection -> Query -> q -> IO Int64
execute conn template qs = do
result <- exec conn =<< formatQuery conn template qs
finishExecute conn template result
-- | A version of 'execute' that does not perform query substitution.
execute_ :: Connection -> Query -> IO Int64
execute_ conn q@(Query stmt) = do
result <- exec conn stmt
finishExecute conn q result
-- | Execute a multi-row @INSERT@, @UPDATE@, or other SQL query that is not
-- expected to return results.
--
-- Returns the number of rows affected.
--
-- Throws 'FormatError' if the query could not be formatted correctly.
executeMany :: (QueryParams q) => Connection -> Query -> [q] -> IO Int64
executeMany _ _ [] = return 0
executeMany conn q qs = do
result <- exec conn =<< formatMany conn q qs
finishExecute conn q result
finishExecute :: Connection -> Query -> PQ.Result -> IO Int64
finishExecute conn q result = do
status <- PQ.resultStatus result
case status of
PQ.CommandOk -> do
ncols <- PQ.nfields result
if ncols /= 0
then throwIO $ QueryError ("execute resulted in " ++ show ncols ++
"-column result") q
else do
nstr <- PQ.cmdTuples result
return $ case nstr of
Nothing -> 0 -- is this appropriate?
Just str -> toInteger str
PQ.TuplesOk -> do
ncols <- PQ.nfields result
throwIO $ QueryError ("execute resulted in " ++ show ncols ++
"-column result") q
PQ.CopyIn -> fail "FIXME: postgresql-simple does not currently support COPY IN"
PQ.CopyOut -> fail "FIXME: postgresql-simple does not currently support COPY OUT"
_ -> do
errormsg <- maybe "" id <$> PQ.resultErrorMessage result
statusmsg <- PQ.resStatus status
state <- maybe "" id <$> PQ.resultErrorField result PQ.DiagSqlstate
throwIO $ SqlError { sqlState = state
, sqlNativeError = fromEnum status
, sqlErrorMsg = B.concat [ "execute: ", statusmsg
, ": ", errormsg ]}
where
toInteger str = B.foldl' delta 0 str
where
delta acc c =
if '0' <= c && c <= '9'
then 10 * acc + fromIntegral (ord c - ord '0')
else error ("finishExecute: not an int: " ++ B.unpack str)
-- | Perform a @SELECT@ or other SQL query that is expected to return
-- results. All results are retrieved and converted before this
-- function returns.
--
-- When processing large results, this function will consume a lot of
-- client-side memory. Consider using 'fold' instead.
--
-- Exceptions that may be thrown:
--
-- * 'FormatError': the query string could not be formatted correctly.
--
-- * 'QueryError': the result contains no columns (i.e. you should be
-- using 'execute' instead of 'query').
--
-- * 'ResultError': result conversion failed.
query :: (QueryParams q, QueryResults r)
=> Connection -> Query -> q -> IO [r]
query conn template qs = do
result <- exec conn =<< formatQuery conn template qs
finishQuery conn template result
-- | A version of 'query' that does not perform query substitution.
query_ :: (QueryResults r) => Connection -> Query -> IO [r]
query_ conn q@(Query que) = do
result <- exec conn que
finishQuery conn q result
{--
-- | Perform a @SELECT@ or other SQL query that is expected to return
-- results. Results are streamed incrementally from the server, and
-- consumed via a left fold.
--
-- The result consumer must be carefully written to execute
-- quickly. If the consumer is slow, server resources will be tied up,
-- and other clients may not be able to update the tables from which
-- the results are being streamed.
--
-- 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.
--
-- Exceptions that may be thrown:
--
-- * 'FormatError': the query string could not be formatted correctly.
--
-- * 'QueryError': the result contains no columns (i.e. you should be
-- using 'execute' instead of 'query').
--
-- * 'ResultError': result conversion failed.
fold :: (QueryParams q, QueryResults r) =>
Connection
-> Query -- ^ Query template.
-> q -- ^ Query parameters.
-> a -- ^ Initial state for result consumer.
-> (a -> r -> IO a) -- ^ Result consumer.
-> IO a
fold conn template qs z f = do
Base.query conn =<< formatQuery conn template qs
finishFold conn template z f
--}
{--
-- | A version of 'fold' that does not perform query substitution.
fold_ :: (QueryResults r) =>
Connection
-> Query -- ^ Query.
-> a -- ^ Initial state for result consumer.
-> (a -> r -> IO a) -- ^ Result consumer.
-> IO a
fold_ conn q@(Query que) z f = do
Base.query conn que
finishFold conn q z f
--}
{--
-- | A version of 'fold' that does not transform a state value.
forEach :: (QueryParams q, QueryResults r) =>
Connection
-> Query -- ^ Query template.
-> q -- ^ Query parameters.
-> (r -> IO ()) -- ^ Result consumer.
-> IO ()
forEach conn template qs = fold conn template qs () . const
{-# INLINE forEach #-}
-- | A version of 'forEach' that does not perform query substitution.
forEach_ :: (QueryResults r) =>
Connection
-> Query -- ^ Query template.
-> (r -> IO ()) -- ^ Result consumer.
-> IO ()
forEach_ conn template = fold_ conn template () . const
{-# INLINE forEach_ #-}
--}
forM' :: (Ord n, Num n) => n -> n -> (n -> IO a) -> IO [a]
forM' lo hi m = loop hi []
where
loop !n !as
| n < lo = return as
| otherwise = do
a <- m n
loop (n-1) (a:as)
finishQuery :: (QueryResults r) => Connection -> Query -> PQ.Result -> IO [r]
finishQuery conn q result = do
status <- PQ.resultStatus result
case status of
PQ.CommandOk -> do
throwIO $ QueryError "query resulted in a command response" q
PQ.TuplesOk -> do
ncols <- PQ.nfields result
fields <- forM' 0 (ncols-1) $ \column -> do
type_oid <- PQ.ftype result column
typename <- getTypename conn type_oid
return Field{..}
nrows <- PQ.ntuples result
forM' 0 (nrows-1) $ \row -> do
values <- forM' 0 (ncols-1) (\col -> PQ.getvalue' result row col)
case convertResults fields values of
Left err -> throwIO err
Right a -> return a
PQ.CopyIn -> fail "FIXME: postgresql-simple does not currently support COPY IN"
PQ.CopyOut -> fail "FIXME: postgresql-simple does not currently support COPY OUT"
_ -> do
errormsg <- maybe "" id <$> PQ.resultErrorMessage result
statusmsg <- PQ.resStatus status
state <- maybe "" id <$> PQ.resultErrorField result PQ.DiagSqlstate
throwIO $ SqlError { sqlState = state
, sqlNativeError = fromEnum status
, sqlErrorMsg = B.concat [ "query: ", statusmsg
, ": ", errormsg ]}
{--
withResult (Base.storeResult conn) q $ \r fs -> do
status <-
/ flip fix [] $ \loop acc -> do
row <- Base.fetchRow r
case row of
[] -> return (reverse acc)
_ -> let !c = convertResults fs row
in loop (c:acc)
--}
{--
finishFold :: (QueryResults r) =>
Connection -> Query -> a -> (a -> r -> IO a) -> IO a
finishFold conn q z0 f = withResult (Base.useResult conn) q $ \r fs ->
flip fix z0 $ \loop z -> do
row <- Base.fetchRow r
case row of
[] -> return z
_ -> (f z $! convertResults fs row) >>= loop
--}
{--
withResult :: (IO Result) -> Query -> (Result -> [Field] -> IO a) -> IO a
withResult fetchResult q act = bracket fetchResult Base.freeResult $ \r -> do
ncols <- Base.fieldCount (Right r)
if ncols == 0
then throwIO $ QueryError "query resulted in zero-column result" q
else act r =<< Base.fetchFields r
--}
-- | Execute an action inside a SQL transaction.
--
-- This function initiates a transaction with a \"@begin
-- transaction@\" statement, then executes the supplied action. If
-- the action succeeds, the transaction will be completed with
-- 'Base.commit' before this function returns.
--
-- If the action throws /any/ kind of exception (not just a
-- PostgreSQL-related exception), the transaction will be rolled back using
-- 'rollback', then the exception will be rethrown.
withTransaction :: Connection -> IO a -> IO a
withTransaction conn act = do
_ <- begin conn
r <- act `onException` rollback conn
commit conn
return r
-- | Rollback a transaction.
-- rollback :: (MonadCatchIO m,MonadIO m) => Connection -> m ()
rollback :: Connection -> IO ()
rollback conn = do
_ <- execute_ conn "ABORT"
return ()
-- | Commit a transaction.
-- commit :: (MonadCatchIO m,MonadIO m) => Connection -> m ()
commit :: Connection -> IO ()
commit conn = do
_ <- execute_ conn "COMMIT"
return ()
-- | Begin a transaction.
-- begin :: (MonadCatchIO m,MonadIO m) => Connection -> m ()
begin :: Connection -> IO ()
begin conn = do
_ <- execute_ conn "BEGIN"
return ()
fmtError :: String -> Query -> [Action] -> a
fmtError msg q xs = throw FormatError {
fmtMessage = msg
, fmtQuery = q
, fmtParams = map twiddle xs
}
where twiddle (Plain b) = toByteString b
twiddle (Escape s) = s
twiddle (Many ys) = B.concat (map twiddle ys)
-- $use
--
-- SQL-based applications are somewhat notorious for their
-- susceptibility to attacks through the injection of maliciously
-- crafted data. The primary reason for widespread vulnerability to
-- SQL injections is that many applications are sloppy in handling
-- user data when constructing SQL queries.
--
-- This library provides a 'Query' type and a parameter substitution
-- facility to address both ease of use and security.
-- $querytype
--
-- A 'Query' is a @newtype@-wrapped 'ByteString'. It intentionally
-- exposes a tiny API that is not compatible with the 'ByteString'
-- API; this makes it difficult to construct queries from fragments of
-- strings. The 'query' and 'execute' functions require queries to be
-- of type 'Query'.
--
-- To most easily construct a query, enable GHC's @OverloadedStrings@
-- language extension and write your query as a normal literal string.
--
-- > {-# LANGUAGE OverloadedStrings #-}
-- >
-- > import Database.PostgreSQL.Simple
-- >
-- > hello = do
-- > conn <- connect defaultConnectInfo
-- > query conn "select 2 + 2"
--
-- A 'Query' value does not represent the actual query that will be
-- executed, but is a template for constructing the final query.
-- $subst
--
-- Since applications need to be able to construct queries with
-- parameters that change, this library provides a query substitution
-- capability.
--
-- The 'Query' template accepted by 'query' and 'execute' can contain
-- any number of \"@?@\" characters. Both 'query' and 'execute'
-- accept a third argument, typically a tuple. When constructing the
-- real query to execute, these functions replace the first \"@?@\" in
-- the template with the first element of the tuple, the second
-- \"@?@\" with the second element, and so on. If necessary, each
-- tuple element will be quoted and escaped prior to substitution;
-- this defeats the single most common injection vector for malicious
-- data.
--
-- For example, given the following 'Query' template:
--
-- > select * from user where first_name = ? and age > ?
--
-- And a tuple of this form:
--
-- > ("Boris" :: String, 37 :: Int)
--
-- The query to be executed will look like this after substitution:
--
-- > select * from user where first_name = 'Boris' and age > 37
--
-- If there is a mismatch between the number of \"@?@\" characters in
-- your template and the number of elements in your tuple, a
-- 'FormatError' will be thrown.
--
-- Note that the substitution functions do not attempt to parse or
-- validate your query. It's up to you to write syntactically valid
-- SQL, and to ensure that each \"@?@\" in your query template is
-- matched with the right tuple element.
-- $inference
--
-- Automated type inference means that you will often be able to avoid
-- supplying explicit type signatures for the elements of a tuple.
-- However, sometimes the compiler will not be able to infer your
-- types. Consider a care where you write a numeric literal in a
-- parameter tuple:
--
-- > query conn "select ? + ?" (40,2)
--
-- The above query will be rejected by the compiler, because it does
-- not know the specific numeric types of the literals @40@ and @2@.
-- This is easily fixed:
--
-- > query conn "select ? + ?" (40 :: Double, 2 :: Double)
--
-- The same kind of problem can arise with string literals if you have
-- the @OverloadedStrings@ language extension enabled. Again, just
-- use an explicit type signature if this happens.
-- $only_param
--
-- Haskell lacks a single-element tuple type, so if you have just one
-- value you want substituted into a query, what should you do?
--
-- The obvious approach would appear to be something like this:
--
-- > instance (Param a) => QueryParam a where
-- > ...
--
-- Unfortunately, this wreaks havoc with type inference, so we take a
-- different tack. To represent a single value @val@ as a parameter, write
-- a singleton list @[val]@, use 'Just' @val@, or use 'Only' @val@.
--
-- Here's an example using a singleton list:
--
-- > execute conn "insert into users (first_name) values (?)"
-- > ["Nuala"]
-- $in
--
-- Suppose you want to write a query using an @IN@ clause:
--
-- > select * from users where first_name in ('Anna', 'Boris', 'Carla')
--
-- In such cases, it's common for both the elements and length of the
-- list after the @IN@ keyword to vary from query to query.
--
-- To address this case, use the 'In' type wrapper, and use a single
-- \"@?@\" character to represent the list. Omit the parentheses
-- around the list; these will be added for you.
--
-- Here's an example:
--
-- > query conn "select * from users where first_name in ?" $
-- > In ["Anna", "Boris", "Carla"]
--
-- If your 'In'-wrapped list is empty, the string @\"(null)\"@ will be
-- substituted instead, to ensure that your clause remains
-- syntactically valid.
-- $many
--
-- If you know that you have many rows of data to insert into a table,
-- it is much more efficient to perform all the insertions in a single
-- multi-row @INSERT@ statement than individually.
--
-- The 'executeMany' function is intended specifically for helping
-- with multi-row @INSERT@ and @UPDATE@ statements. Its rules for
-- query substitution are different than those for 'execute'.
--
-- What 'executeMany' searches for in your 'Query' template is a
-- single substring of the form:
--
-- > values (?,?,?)
--
-- The rules are as follows:
--
-- * The keyword @VALUES@ is matched case insensitively.
--
-- * There must be no other \"@?@\" characters anywhere in your
-- template.
--
-- * There must one or more \"@?@\" in the parentheses.
--
-- * Extra white space is fine.
--
-- The last argument to 'executeMany' is a list of parameter
-- tuples. These will be substituted into the query where the @(?,?)@
-- string appears, in a form suitable for use in a multi-row @INSERT@
-- or @UPDATE@.
--
-- Here is an example:
--
-- > executeMany conn
-- > "insert into users (first_name,last_name) values (?,?)"
-- > [("Boris","Karloff"),("Ed","Wood")]
--
-- The query that will be executed here will look like this
-- (reformatted for tidiness):
--
-- > insert into users (first_name,last_name) values
-- > ('Boris','Karloff'),('Ed','Wood')
-- $result
--
-- The 'query' and 'query_' functions return a list of values in the
-- 'QueryResults' typeclass. This class performs automatic extraction
-- and type conversion of rows from a query result.
--
-- Here is a simple example of how to extract results:
--
-- > import qualified Data.Text as Text
-- >
-- > xs <- query_ conn "select name,age from users"
-- > forM_ xs $ \(name,age) ->
-- > putStrLn $ Text.unpack name ++ " is " ++ show (age :: Int)
--
-- Notice two important details about this code:
--
-- * The number of columns we ask for in the query template must
-- exactly match the number of elements we specify in a row of the
-- result tuple. If they do not match, a 'ResultError' exception
-- will be thrown.
--
-- * Sometimes, the compiler needs our help in specifying types. It
-- can infer that @name@ must be a 'Text', due to our use of the
-- @unpack@ function. However, we have to tell it the type of @age@,
-- as it has no other information to determine the exact type.
-- $null
--
-- The type of a result tuple will look something like this:
--
-- > (Text, Int, Int)
--
-- Although SQL can accommodate @NULL@ as a value for any of these
-- types, Haskell cannot. If your result contains columns that may be
-- @NULL@, be sure that you use 'Maybe' in those positions of of your
-- tuple.
--
-- > (Text, Maybe Int, Int)
--
-- If 'query' encounters a @NULL@ in a row where the corresponding
-- Haskell type is not 'Maybe', it will throw a 'ResultError'
-- exception.
-- $only_result
--
-- To specify that a query returns a single-column result, use the
-- 'Only' type.
--
-- > xs <- query_ conn "select id from users"
-- > forM_ xs $ \(Only dbid) -> {- ... -}
-- $types
--
-- Conversion of SQL values to Haskell values is somewhat
-- permissive. Here are the rules.
--
-- * For numeric types, any Haskell type that can accurately represent
-- all values of the given PostgreSQL type is considered \"compatible\".
-- For instance, you can always extract a PostgreSQL 16-bit @SMALLINT@
-- column to a Haskell 'Int'. The Haskell 'Float' type can accurately
-- represent a @SMALLINT@, so it is considered compatble with those types.
--
-- * A numeric compatibility check is based only on the type of a
-- column, /not/ on its values. For instance, a PostgreSQL 64-bit
-- @BIGINT@ column will be considered incompatible with a Haskell
-- 'Int16', even if it contains the value @1@.
--
-- * If a numeric incompatibility is found, 'query' will throw a
-- 'ResultError'.
--
-- * The 'String' and 'Text' types are assumed to be encoded as
-- UTF-8. If you use some other encoding, decoding may fail or give
-- wrong results. In such cases, write a @newtype@ wrapper and a
-- custom 'Result' instance to handle your encoding.
getTypename :: Connection -> PQ.Oid -> IO ByteString
getTypename conn@Connection{..} oid =
case oid2builtin oid of
Just builtin -> return $! builtin2typname builtin
Nothing -> modifyMVar connectionObjects $ \oidmap -> do
case IntMap.lookup (oid2int oid) oidmap of
Just name -> return (oidmap, name)
Nothing -> do
names <- query conn "SELECT typname FROM pg_type WHERE oid=?"
(Only oid)
name <- case names of
[] -> return $ throw SqlError {
sqlNativeError = -1,
sqlErrorMsg = "invalid type oid",
sqlState = ""
}
[Only x] -> return x
_ -> fail "typename query returned more than one result"
-- oid is a primary key, so the query should
-- never return more than one result
return (IntMap.insert (oid2int oid) name oidmap, name)