@@ -1,14 +1,18 @@
1−{-# LANGUAGE DeriveDataTypeable, RecordWildCards, NamedFieldPuns #-}
1+{-# LANGUAGE DeriveDataTypeable #-}
2+{-# LANGUAGE NamedFieldPuns #-}
3+{-# LANGUAGE OverloadedStrings #-}
4+{-# LANGUAGE PatternGuards #-}
5+{-# LANGUAGE RecordWildCards #-}
6+{-# LANGUAGE ViewPatterns #-}
3------------------------------------------------------------------------------
8------------------------------------------------------------------------------
5-- Module: Database.PostgreSQL.Simple
10-- Module: Database.PostgreSQL.Simple
6-- Copyright: (c) 2011 MailRank, Inc.
11-- Copyright: (c) 2011 MailRank, Inc.
7−-- (c) 2011 Leon P Smith
12+-- (c) 2011-2012 Leon P Smith
8-- License: BSD3
13-- License: BSD3
9-- Maintainer: Leon P Smith <leon@melding-monads.com>
14-- Maintainer: Leon P Smith <leon@melding-monads.com>
10-- Stability: experimental
15-- Stability: experimental
11−-- Portability: portable
13-- A mid-level client library for the PostgreSQL database, aimed at ease of
17-- A mid-level client library for the PostgreSQL database, aimed at ease of
14-- use and high performance.
18-- use and high performance.
@@ -38,6 +42,9 @@ module Database.PostgreSQL.Simple
38 -- ** Modifying multiple rows at once
42 -- ** Modifying multiple rows at once
45+ -- ** @RETURNING@: modifications that return results
41 -- * Extracting results
48 -- * Extracting results
42 -- $result
49 -- $result
@@ -48,26 +55,35 @@ module Database.PostgreSQL.Simple
50 -- * Types
57 -- * Types
52− , Connection
58+ Connection
55 , Binary(..)
63 , Binary(..)
56 , Only(..)
64 , Only(..)
57 -- ** Exceptions
66 -- ** Exceptions
67+ , SomePostgreSqlException(..)
58 , SqlError(..)
68 , SqlError(..)
59− , FormatError(fmtMessage, fmtQuery, fmtParams)
70+ , FormatError(..)
60− , QueryError(qeMessage, qeQuery)
71+ , QueryError(..)
61− , ResultError(errSQLType, errHaskellType, errMessage)
72+ , ResultError(..)
62 -- * Connection management
73 -- * Connection management
64 , Base.connectPostgreSQL
74 , Base.connectPostgreSQL
65− , Base.postgreSQLConnectionString
66− , Base.defaultConnectInfo
67 , Base.close
75 , Base.close
78+ , Base.ConnectInfo(..)
79+ , Base.defaultConnectInfo
80+ , Base.postgreSQLConnectionString
68 -- * Queries that return results
81 -- * Queries that return results
84+ -- ** Queries taking parser as argument
71 -- * Queries that stream results
87 -- * Queries that stream results
72 , FoldOptions(..)
88 , FoldOptions(..)
73 , FetchQuantity(..)
89 , FetchQuantity(..)
@@ -78,6 +94,15 @@ module Database.PostgreSQL.Simple
78 , foldWithOptions_
94 , foldWithOptions_
80 , forEach_
96 , forEach_
98+ -- ** Queries that stream results taking a parser as an argument
100+ , foldWithOptionsAndParser
102+ , foldWithOptionsAndParser_
81 -- * Statements that do not return results
106 -- * Statements that do not return results
82 , execute
107 , execute
83 , execute_
108 , execute_
@@ -85,18 +110,9 @@ module Database.PostgreSQL.Simple
85-- , Base.insertID
110-- , Base.insertID
86 -- * Transaction handling
111 -- * Transaction handling
87 , withTransaction
112 , withTransaction
88− , TransactionMode(..)
113+ , withSavepoint
91− , defaultTransactionMode
92− , defaultIsolationLevel
93− , defaultReadWriteMode
94− , withTransactionLevel
95− , withTransactionMode
96-- , Base.autocommit
114-- , Base.autocommit
101 , rollback
117 , rollback
102 -- * Helper functions
118 -- * Helper functions
@@ -104,50 +120,27 @@ module Database.PostgreSQL.Simple
104 , formatQuery
120 , formatQuery
107−import Blaze.ByteString.Builder
123+import Data.ByteString.Builder (Builder, byteString, char8)
108− ( Builder, fromByteString, toByteString )
109−import Blaze.ByteString.Builder.Char8 (fromChar)
110−import Control.Applicative ((<$>), pure)
124+import Control.Applicative ((<$>))
111−import Control.Concurrent.MVar
125+import Control.Exception as E
112−import Control.Exception
113− ( Exception, onException, throw, throwIO, finally )
114−import Control.Monad (foldM)
115import Data.ByteString (ByteString)
126import Data.ByteString (ByteString)
116import Data.Int (Int64)
127import Data.Int (Int64)
117−import qualified Data.IntMap as IntMap
118import Data.List (intersperse)
128import Data.List (intersperse)
119−import Data.Monoid (mappend, mconcat)
129+import Data.Monoid (mconcat)
120−import Data.Typeable (Typeable)
121−import Database.PostgreSQL.Simple.BuiltinTypes
122− ( oid2builtin, builtin2typname )
123−import Database.PostgreSQL.Simple.Compat ( mask )
130+import Database.PostgreSQL.Simple.Compat ((<>), toByteString)
131+import Database.PostgreSQL.Simple.Cursor
124import Database.PostgreSQL.Simple.FromField (ResultError(..))
132import Database.PostgreSQL.Simple.FromField (ResultError(..))
125import Database.PostgreSQL.Simple.FromRow (FromRow(..))
133import Database.PostgreSQL.Simple.FromRow (FromRow(..))
126−import Database.PostgreSQL.Simple.Ok
134+import Database.PostgreSQL.Simple.ToField (Action(..))
127−import Database.PostgreSQL.Simple.ToField (Action(..), inQuotes)
128import Database.PostgreSQL.Simple.ToRow (ToRow(..))
135import Database.PostgreSQL.Simple.ToRow (ToRow(..))
129import Database.PostgreSQL.Simple.Types
136import Database.PostgreSQL.Simple.Types
130− ( Binary(..), In(..), Only(..), Query(..) )
137+ ( Binary(..), In(..), Only(..), Query(..), (:.)(..) )
131import Database.PostgreSQL.Simple.Internal as Base
138import Database.PostgreSQL.Simple.Internal as Base
139+import Database.PostgreSQL.Simple.Internal.PQResultUtils
140+import Database.PostgreSQL.Simple.Transaction
132import qualified Database.PostgreSQL.LibPQ as PQ
141import qualified Database.PostgreSQL.LibPQ as PQ
133−import Text.Regex.PCRE.Light (compile, caseless, match)
134import qualified Data.ByteString.Char8 as B
142import qualified Data.ByteString.Char8 as B
135−import qualified Data.Text as T
143+
136−import qualified Data.Text.Encoding as TE
137−import qualified Data.Vector as V
138−import Control.Monad.Trans.Reader
139−import Control.Monad.Trans.State.Strict
141−-- | Exception thrown if a 'Query' could not be formatted correctly.
142−-- This may occur if the number of \'@?@\' characters in the query
143−-- string does not match the number of parameters provided.
144−data FormatError = FormatError {
145− fmtMessage :: String
147− , fmtParams :: [ByteString]
148− } deriving (Eq, Show, Typeable)
150−instance Exception FormatError
152-- | Format a query string.
145-- | Format a query string.
@@ -181,56 +174,143 @@ formatQuery conn q@(Query template) qs
181formatMany :: (ToRow q) => Connection -> Query -> [q] -> IO ByteString
174formatMany :: (ToRow q) => Connection -> Query -> [q] -> IO ByteString
182formatMany _ q [] = fmtError "no rows supplied" q []
175formatMany _ q [] = fmtError "no rows supplied" q []
183formatMany conn q@(Query template) qs = do
176formatMany conn q@(Query template) qs = do
184− case match re template [] of
177+ case parseTemplate template of
185− Just [_,before,qbits,after] -> do
178+ Just (before, qbits, after) -> do
186 bs <- mapM (buildQuery conn q qbits . toRow) qs
179 bs <- mapM (buildQuery conn q qbits . toRow) qs
187− return . toByteString . mconcat $ fromByteString before :
180+ return . toByteString . mconcat $ byteString before :
188− intersperse (fromChar ',') bs ++
181+ intersperse (char8 ',') bs ++
189− [fromByteString after]
182+ [byteString after]
190− _ -> error "foo"
183+ Nothing -> fmtError "syntax error in multi-row template" q []
185+-- Split the input string into three pieces, @before@, @qbits@, and @after@,
186+-- following this grammar:
188+-- start: ^ before qbits after $
189+-- before: ([^?]* [^?\w])? 'VALUES' \s*
190+-- qbits: '(' \s* '?' \s* (',' \s* '?' \s*)* ')'
194+-- \w: [A-Z] | [a-z] | [\x80-\xFF] | '_' | '$' | [0-9]
196+-- This would be much more concise with some sort of regex engine.
197+-- 'formatMany' used to use pcre-light instead of this hand-written parser,
198+-- but pcre is a hassle to install on Windows.
199+parseTemplate :: ByteString -> Maybe (ByteString, ByteString, ByteString)
200+parseTemplate template =
201+ -- Convert input string to uppercase, to facilitate searching.
202+ search $ B.map toUpper_ascii template
192− re = compile "^([^?]+\\bvalues\\s*)\
204+ -- Search for the next occurrence of "VALUES"
193− \(\\(\\s*[?](?:\\s*,\\s*[?])*\\s*\\))\
205+ search bs =
194− \([^?]*)$"
206+ case B.breakSubstring "VALUES" bs of
195− [caseless]
207+ (x, y)
196−
208+ -- If "VALUES" is not present in the string, or any '?' characters
197−escapeStringConn :: Connection -> ByteString -> IO (Either ByteString ByteString)
209+ -- were encountered prior to it, fail.
198−escapeStringConn conn s =
210+ | B.null y || ('?' `B.elem` x)
199− withConnection conn $ \c ->
211+ -> Nothing
200− PQ.escapeStringConn c s >>= checkError c
212+
213+ -- If "VALUES" is preceded by an identifier character (a.k.a. \w),
214+ -- try the next occurrence.
215+ | not (B.null x) && isIdent (B.last x)
216+ -> search $ B.drop 6 y
218+ -- Otherwise, we have a legitimate "VALUES" token.
220+ -> parseQueryBits $ skipSpace $ B.drop 6 y
222+ -- Parse '(' \s* '?' \s* . If this doesn't match
223+ -- (and we don't consume a '?'), look for another "VALUES".
225+ -- qb points to the open paren (if present), meaning it points to the
226+ -- beginning of the "qbits" production described above. This is why we
227+ -- pass it down to finishQueryBits.
229+ | Just ('(', skipSpace -> bs1) <- B.uncons qb
230+ , Just ('?', skipSpace -> bs2) <- B.uncons bs1
231+ = finishQueryBits qb bs2
235+ -- Parse (',' \s* '?' \s*)* ')' [^?]* .
237+ -- Since we've already consumed at least one '?', there's no turning back.
238+ -- The parse has to succeed here, or the whole thing fails
239+ -- (because we don't allow '?' to appear outside of the VALUES list).
240+ finishQueryBits qb bs0
241+ | Just (')', bs1) <- B.uncons bs0
242+ = if '?' `B.elem` bs1
244+ else Just $ slice3 template qb bs1
245+ | Just (',', skipSpace -> bs1) <- B.uncons bs0
246+ , Just ('?', skipSpace -> bs2) <- B.uncons bs1
247+ = finishQueryBits qb bs2
251+ -- Slice a string into three pieces, given the start offset of the second
252+ -- and third pieces. Each "offset" is actually a tail of the uppercase
253+ -- version of the template string. Its length is used to infer the offset.
255+ -- It is important to note that we only slice the original template.
256+ -- We don't want our all-caps trick messing up the actual query string.
257+ slice3 source p1 p2 =
260+ (s1, source') = B.splitAt (B.length source - B.length p1) source
261+ (s2, source'') = B.splitAt (B.length p1 - B.length p2) source'
263+ toUpper_ascii c | c >= 'a' && c <= 'z' = toEnum (fromEnum c - 32)
266+ -- Based on the definition of {ident_cont} in src/backend/parser/scan.l
267+ -- in the PostgreSQL source. No need to check [a-z], since we converted
268+ -- the whole string to uppercase.
269+ isIdent c = (c >= '0' && c <= '9')
270+ || (c >= 'A' && c <= 'Z')
271+ || (c >= '\x80' && c <= '\xFF')
275+ -- Based on {space} in scan.l
276+ isSpace_ascii c = (c == ' ') || (c >= '\t' && c <= '\r')
278+ skipSpace = B.dropWhile isSpace_ascii
202−escapeByteaConn :: Connection -> ByteString -> IO (Either ByteString ByteString)
203−escapeByteaConn conn s =
204− withConnection conn $ \c ->
205− PQ.escapeByteaConn c s >>= checkError c
207−checkError :: PQ.Connection -> Maybe a -> IO (Either ByteString a)
208−checkError _ (Just x) = return $ Right x
209−checkError c Nothing = Left . maybe "" id <$> PQ.errorMessage c
211buildQuery :: Connection -> Query -> ByteString -> [Action] -> IO Builder
281buildQuery :: Connection -> Query -> ByteString -> [Action] -> IO Builder
212−buildQuery conn q template xs = zipParams (split template) <$> mapM sub xs
282+buildQuery conn q template xs =
213− where quote = either (\msg -> fmtError (utf8ToString msg) q xs)
283+ zipParams (split template) <$> mapM (buildAction conn q xs) xs
214− (inQuotes . fromByteString)
284+ where split s =
215− utf8ToString = T.unpack . TE.decodeUtf8
285+ -- This part escapes double '??'s to make literal '?'s possible
216− sub (Plain b) = pure b
286+ -- in PostgreSQL queries using the JSON operators: @?@, @?|@ and @?&@
217− sub (Escape s) = quote <$> escapeStringConn conn s
287+ let (h,t) = breakOnSingleQuestionMark s
218− sub (EscapeBytea s) = quote <$> escapeByteaConn conn s
288+ in byteString h
219− sub (Many ys) = mconcat <$> mapM sub ys
289+ : if B.null t
220− split s = fromByteString h : if B.null t then [] else split (B.tail t)
291+ else split (B.tail t)
221− where (h,t) = B.break (=='?') s
222− zipParams (t:ts) (p:ps) = t `mappend` p `mappend` zipParams ts ps
292+ zipParams (t:ts) (p:ps) = t <> p <> zipParams ts ps
223 zipParams [t] [] = t
293 zipParams [t] [] = t
224− zipParams _ _ = fmtError (show (B.count '?' template) ++
294+ zipParams _ _ = fmtError (show countSingleQs ++
225− " '?' characters, but " ++
295+ " single '?' characters, but " ++
226 show (length xs) ++ " parameters") q xs
296 show (length xs) ++ " parameters") q xs
297+ countSingleQs = go 0 template
298+ where go i "" = (i :: Int)
299+ go i bs = case qms of
300+ ("?","?") -> go i nextQMBS
301+ ("?",_) -> go (i+1) nextQMBS
303+ where qms = B.splitAt 1 qmBS
304+ (qmBS,nextQMBS) = B.splitAt 2 qmBS'
305+ qmBS' = B.dropWhile (/= '?') bs
228-- | Execute an @INSERT@, @UPDATE@, or other SQL query that is not
307-- | Execute an @INSERT@, @UPDATE@, or other SQL query that is not
229-- expected to return results.
308-- expected to return results.
231-- Returns the number of rows affected.
310-- Returns the number of rows affected.
233−-- Throws 'FormatError' if the query could not be formatted correctly.
312+-- Throws 'FormatError' if the query could not be formatted correctly, or
313+-- a 'SqlError' exception if the backend returns an error.
234execute :: (ToRow q) => Connection -> Query -> q -> IO Int64
314execute :: (ToRow q) => Connection -> Query -> q -> IO Int64
235execute conn template qs = do
315execute conn template qs = do
236 result <- exec conn =<< formatQuery conn template qs
316 result <- exec conn =<< formatQuery conn template qs
@@ -239,15 +319,61 @@ execute conn template qs = do
239-- | Execute a multi-row @INSERT@, @UPDATE@, or other SQL query that is not
319-- | Execute a multi-row @INSERT@, @UPDATE@, or other SQL query that is not
240-- expected to return results.
320-- expected to return results.
242−-- Returns the number of rows affected.
322+-- Returns the number of rows affected. If the list of parameters is empty,
323+-- this function will simply return 0 without issuing the query to the backend.
324+-- If this is not desired, consider using the 'Values' constructor instead.
244−-- Throws 'FormatError' if the query could not be formatted correctly.
326+-- Throws 'FormatError' if the query could not be formatted correctly, or
327+-- a 'SqlError' exception if the backend returns an error.
329+-- For example, here's a command that inserts two rows into a table
333+-- executeMany c [sql|
334+-- INSERT INTO sometable VALUES (?,?)
335+-- |] [(1, \"hello\"),(2, \"world\")]
338+-- Here's an canonical example of a multi-row update command:
341+-- executeMany c [sql|
344+-- FROM (VALUES (?,?)) as upd(x,y)
345+-- WHERE sometable.x = upd.x
346+-- |] [(1, \"hello\"),(2, \"world\")]
245executeMany :: (ToRow q) => Connection -> Query -> [q] -> IO Int64
349executeMany :: (ToRow q) => Connection -> Query -> [q] -> IO Int64
246executeMany _ _ [] = return 0
350executeMany _ _ [] = return 0
247executeMany conn q qs = do
351executeMany conn q qs = do
248 result <- exec conn =<< formatMany conn q qs
352 result <- exec conn =<< formatMany conn q qs
249 finishExecute conn q result
353 finishExecute conn q result
355+-- | Execute @INSERT ... RETURNING@, @UPDATE ... RETURNING@, or other SQL
356+-- query that accepts multi-row input and is expected to return results.
357+-- Note that it is possible to write
358+-- @'query' conn "INSERT ... RETURNING ..." ...@
359+-- in cases where you are only inserting a single row, and do not need
360+-- functionality analogous to 'executeMany'.
362+-- If the list of parameters is empty, this function will simply return @[]@
363+-- without issuing the query to the backend. If this is not desired,
364+-- consider using the 'Values' constructor instead.
366+-- Throws 'FormatError' if the query could not be formatted correctly.
367+returning :: (ToRow q, FromRow r) => Connection -> Query -> [q] -> IO [r]
368+returning = returningWith fromRow
370+-- | A version of 'returning' taking parser as argument
371+returningWith :: (ToRow q) => RowParser r -> Connection -> Query -> [q] -> IO [r]
372+returningWith _ _ _ [] = return []
373+returningWith parser conn q qs = do
374+ result <- exec conn =<< formatMany conn q qs
375+ finishQueryWith parser conn q result
251-- | Perform a @SELECT@ or other SQL query that is expected to return
377-- | Perform a @SELECT@ or other SQL query that is expected to return
252-- results. All results are retrieved and converted before this
378-- results. All results are retrieved and converted before this
253-- function returns.
379-- function returns.
@@ -263,17 +389,27 @@ executeMany conn q qs = do
263-- using 'execute' instead of 'query').
389-- using 'execute' instead of 'query').
265-- * 'ResultError': result conversion failed.
391-- * 'ResultError': result conversion failed.
393+-- * 'SqlError': the postgresql backend returned an error, e.g.
394+-- a syntax or type error, or an incorrect table or column name.
266−query :: (ToRow q, FromRow r)
395+query :: (ToRow q, FromRow r) => Connection -> Query -> q -> IO [r]
267− => Connection -> Query -> q -> IO [r]
396+query = queryWith fromRow
268−query conn template qs = do
269− result <- exec conn =<< formatQuery conn template qs
270− finishQuery conn template result
272-- | A version of 'query' that does not perform query substitution.
398-- | A version of 'query' that does not perform query substitution.
273query_ :: (FromRow r) => Connection -> Query -> IO [r]
399query_ :: (FromRow r) => Connection -> Query -> IO [r]
400+query_ = queryWith_ fromRow
402+-- | A version of 'query' taking parser as argument
403+queryWith :: ToRow q => RowParser r -> Connection -> Query -> q -> IO [r]
404+queryWith parser conn template qs = do
405+ result <- exec conn =<< formatQuery conn template qs
406+ finishQueryWith parser conn template result
408+-- | A version of 'query_' taking parser as argument
409+queryWith_ :: RowParser r -> Connection -> Query -> IO [r]
274−query_ conn q@(Query que) = do
410+queryWith_ parser conn q@(Query que) = do
275 result <- exec conn que
411 result <- exec conn que
276− finishQuery conn q result
412+ finishQueryWith parser conn q result
278-- | Perform a @SELECT@ or other SQL query that is expected to return
414-- | Perform a @SELECT@ or other SQL query that is expected to return
279-- results. Results are streamed incrementally from the server, and
415-- results. Results are streamed incrementally from the server, and
@@ -285,6 +421,12 @@ query_ conn q@(Query que) = do
285-- This fold is /not/ strict. The stream consumer is responsible for
421-- This fold is /not/ strict. The stream consumer is responsible for
286-- forcing the evaluation of its result to avoid space leaks.
422-- forcing the evaluation of its result to avoid space leaks.
424+-- This is implemented using a database cursor. As such, this requires
425+-- a transaction. This function will detect whether or not there is a
426+-- transaction in progress, and will create a 'ReadCommitted' 'ReadOnly'
427+-- transaction if needed. The cursor is given a unique temporary name,
428+-- so the consumer may itself call fold.
288-- Exceptions that may be thrown:
430-- Exceptions that may be thrown:
290-- * 'FormatError': the query string could not be formatted correctly.
432-- * 'FormatError': the query string could not be formatted correctly.
@@ -293,7 +435,9 @@ query_ conn q@(Query que) = do
293-- using 'execute' instead of 'query').
435-- using 'execute' instead of 'query').
295-- * 'ResultError': result conversion failed.
437-- * 'ResultError': result conversion failed.
439+-- * 'SqlError': the postgresql backend returned an error, e.g.
440+-- a syntax or type error, or an incorrect table or column name.
297fold :: ( FromRow row, ToRow params )
441fold :: ( FromRow row, ToRow params )
298 => Connection
442 => Connection
@@ -303,6 +447,20 @@ fold :: ( FromRow row, ToRow params )
304fold = foldWithOptions defaultFoldOptions
448fold = foldWithOptions defaultFoldOptions
450+-- | A version of 'fold' taking a parser as an argument
451+foldWith :: ( ToRow params )
457+ -> (a -> row -> IO a)
459+foldWith = foldWithOptionsAndParser defaultFoldOptions
461+-- | Number of rows to fetch at a time. 'Automatic' currently defaults
462+-- to 256 rows, although it might be nice to make this more intelligent
463+-- based on e.g. the average size of the rows.
306data FetchQuantity
464data FetchQuantity
307 = Automatic
465 = Automatic
308 | Fixed !Int
466 | Fixed !Int
@@ -313,12 +471,19 @@ data FoldOptions
313 transactionMode :: !TransactionMode
471 transactionMode :: !TransactionMode
474+-- | defaults to 'Automatic', and 'TransactionMode' 'ReadCommitted' 'ReadOnly'
316defaultFoldOptions :: FoldOptions
475defaultFoldOptions :: FoldOptions
317defaultFoldOptions = FoldOptions {
476defaultFoldOptions = FoldOptions {
318 fetchQuantity = Automatic,
477 fetchQuantity = Automatic,
319 transactionMode = TransactionMode ReadCommitted ReadOnly
478 transactionMode = TransactionMode ReadCommitted ReadOnly
481+-- | The same as 'fold', but this provides a bit more control over
482+-- lower-level details. Currently, the number of rows fetched per
483+-- round-trip to the server and the transaction mode may be adjusted
484+-- accordingly. If the connection is already in a transaction,
485+-- then the existing transaction is used and thus the 'transactionMode'
486+-- option is ignored.
322foldWithOptions :: ( FromRow row, ToRow params )
487foldWithOptions :: ( FromRow row, ToRow params )
323 => FoldOptions
488 => FoldOptions
324 -> Connection
489 -> Connection
@@ -327,9 +492,21 @@ foldWithOptions :: ( FromRow row, ToRow params )
328 -> (a -> row -> IO a)
493 -> (a -> row -> IO a)
330−foldWithOptions opts conn template qs a f = do
495+foldWithOptions opts = foldWithOptionsAndParser opts fromRow
497+-- | A version of 'foldWithOptions' taking a parser as an argument
498+foldWithOptionsAndParser :: (ToRow params)
505+ -> (a -> row -> IO a)
507+foldWithOptionsAndParser opts parser conn template qs a f = do
331 q <- formatQuery conn template qs
508 q <- formatQuery conn template qs
332− doFold opts conn template (Query q) a f
509+ doFold opts parser conn template (Query q) a f
334-- | A version of 'fold' that does not perform query substitution.
511-- | A version of 'fold' that does not perform query substitution.
335fold_ :: (FromRow r) =>
512fold_ :: (FromRow r) =>
@@ -340,6 +517,14 @@ fold_ :: (FromRow r) =>
341fold_ = foldWithOptions_ defaultFoldOptions
518fold_ = foldWithOptions_ defaultFoldOptions
520+-- | A version of 'fold_' taking a parser as an argument
521+foldWith_ :: RowParser r
527+foldWith_ = foldWithOptionsAndParser_ defaultFoldOptions
344foldWithOptions_ :: (FromRow r) =>
529foldWithOptions_ :: (FromRow r) =>
345 FoldOptions
530 FoldOptions
@@ -348,18 +533,27 @@ foldWithOptions_ :: (FromRow r) =>
348 -> a -- ^ Initial state for result consumer.
533 -> a -- ^ Initial state for result consumer.
349 -> (a -> r -> IO a) -- ^ Result consumer.
534 -> (a -> r -> IO a) -- ^ Result consumer.
351−foldWithOptions_ opts conn query a f = doFold opts conn query query a f
536+foldWithOptions_ opts conn query' a f = doFold opts fromRow conn query' query' a f
353−
538+-- | A version of 'foldWithOptions_' taking a parser as an argument
354−doFold :: ( FromRow row )
539+foldWithOptionsAndParser_ :: FoldOptions
355− => FoldOptions
540+ -> RowParser r
542+ -> Query -- ^ Query.
543+ -> a -- ^ Initial state for result consumer.
544+ -> (a -> r -> IO a) -- ^ Result consumer.
546+foldWithOptionsAndParser_ opts parser conn query' a f = doFold opts parser conn query' query' a f
548+doFold :: FoldOptions
356 -> Connection
550 -> Connection
360 -> (a -> row -> IO a)
554 -> (a -> row -> IO a)
362−doFold FoldOptions{..} conn _template q a f = do
556+doFold FoldOptions{..} parser conn _template q a0 f = do
363 stat <- withConnection conn PQ.transactionStatus
557 stat <- withConnection conn PQ.transactionStatus
364 case stat of
558 case stat of
365 PQ.TransIdle -> withTransactionMode transactionMode conn go
559 PQ.TransIdle -> withTransactionMode transactionMode conn go
@@ -377,11 +571,17 @@ doFold FoldOptions{..} conn _template q a f = do
377 PQ.TransUnknown -> fail "foldWithOpts FIXME: PQ.TransUnknown"
571 PQ.TransUnknown -> fail "foldWithOpts FIXME: PQ.TransUnknown"
378 -- Not sure what this means.
572 -- Not sure what this means.
380− go = do
574+ declare =
381− -- FIXME: what about name clashes with already-declared cursors?
575+ declareCursor conn q
382− _ <- execute_ conn ("DECLARE fold NO SCROLL CURSOR FOR "
576+ fetch cursor a =
383− `mappend` q)
577+ foldForwardWithParser cursor parser chunkSize f a
384− loop a `finally` execute_ conn "CLOSE fold"
578+
579+ go = bracket declare closeCursor $ \cursor ->
580+ let loop a = fetch cursor a >>=
386-- FIXME: choose the Automatic chunkSize more intelligently
586-- FIXME: choose the Automatic chunkSize more intelligently
387-- One possibility is to use the type of the results, although this
587-- One possibility is to use the type of the results, although this
@@ -392,9 +592,6 @@ doFold FoldOptions{..} conn _template q a f = do
392 chunkSize = case fetchQuantity of
592 chunkSize = case fetchQuantity of
393 Automatic -> 256
593 Automatic -> 256
394 Fixed n -> n
594 Fixed n -> n
396− rs <- query conn "FETCH FORWARD ? FROM fold" (Only chunkSize)
397− if null rs then return a else foldM f a rs >>= loop
399-- | A version of 'fold' that does not transform a state value.
596-- | A version of 'fold' that does not transform a state value.
400forEach :: (ToRow q, FromRow r) =>
597forEach :: (ToRow q, FromRow r) =>
@@ -403,188 +600,37 @@ forEach :: (ToRow q, FromRow r) =>
403 -> q -- ^ Query parameters.
600 -> q -- ^ Query parameters.
404 -> (r -> IO ()) -- ^ Result consumer.
601 -> (r -> IO ()) -- ^ Result consumer.
406−forEach conn template qs = fold conn template qs () . const
603+forEach = forEachWith fromRow
407{-# INLINE forEach #-}
604{-# INLINE forEach #-}
606+-- | A version of 'forEach' taking a parser as an argument
607+forEachWith :: ( ToRow q )
614+forEachWith parser conn template qs = foldWith parser conn template qs () . const
615+{-# INLINE forEachWith #-}
409-- | A version of 'forEach' that does not perform query substitution.
617-- | A version of 'forEach' that does not perform query substitution.
410forEach_ :: (FromRow r) =>
618forEach_ :: (FromRow r) =>
411 Connection
619 Connection
412 -> Query -- ^ Query template.
620 -> Query -- ^ Query template.
413 -> (r -> IO ()) -- ^ Result consumer.
621 -> (r -> IO ()) -- ^ Result consumer.
415−forEach_ conn template = fold_ conn template () . const
623+forEach_ = forEachWith_ fromRow
416{-# INLINE forEach_ #-}
624{-# INLINE forEach_ #-}
418−forM' :: (Ord n, Num n) => n -> n -> (n -> IO a) -> IO [a]
626+forEachWith_ :: RowParser r
419−forM' lo hi m = loop hi []
627+ -> Connection
421− loop !n !as
629+ -> (r -> IO ())
422− | n < lo = return as
630+ -> IO ()
423− | otherwise = do
631+forEachWith_ parser conn template = foldWith_ parser conn template () . const
424− a <- m n
632+{-# INLINE forEachWith_ #-}
425− loop (n-1) (a:as)
633+
427−finishQuery :: (FromRow r) => Connection -> Query -> PQ.Result -> IO [r]
428−finishQuery conn q result = do
429− status <- PQ.resultStatus result
432− throwIO $ QueryError "query: Empty query" q
434− throwIO $ QueryError "query resulted in a command response" q
436− ncols <- PQ.nfields result
437− let unCol (PQ.Col x) = fromIntegral x :: Int
438− typenames <- V.generateM (unCol ncols)
439− (\(PQ.Col . fromIntegral -> col) -> do
440− getTypename conn =<< PQ.ftype result col)
441− nrows <- PQ.ntuples result
442− ncols <- PQ.nfields result
443− forM' 0 (nrows-1) $ \row -> do
444− let rw = Row row typenames result
445− case runStateT (runReaderT (unRP fromRow) rw) 0 of
446− Ok (val,col) | col == ncols -> return val
448− vals <- forM' 0 (ncols-1) $ \c -> do
449− v <- PQ.getvalue result row c
450− return ( typenames V.! unCol c
452− throw (ConversionFailed
453− (show (unCol ncols) ++ " values: " ++ show vals)
454− (show (unCol col) ++ " slots in target type")
455− "mismatch between number of columns to \
456− \convert and number in target type")
457− Errors [] -> throwIO $ ConversionFailed "" "" "unknown error"
458− Errors [x] -> throwIO x
459− Errors xs -> throwIO $ ManyErrors xs
461− throwIO $ QueryError "query: COPY TO is not supported" q
463− throwIO $ QueryError "query: COPY FROM is not supported" q
464− PQ.BadResponse -> throwResultError "query" result status
465− PQ.NonfatalError -> throwResultError "query" result status
466− PQ.FatalError -> throwResultError "query" result status
468−ellipsis :: ByteString -> ByteString
470− | B.length bs > 15 = B.take 10 bs `B.append` "[...]"
474−-- | Of the four isolation levels defined by the SQL standard,
475−-- these are the three levels distinguished by PostgreSQL as of version 9.0.
476−-- See <http://www.postgresql.org/docs/9.1/static/transaction-iso.html>
477−-- for more information. Note that prior to PostgreSQL 9.0, 'RepeatableRead'
478−-- was equivalent to 'Serializable'.
481− = DefaultIsolationLevel -- ^ the isolation level will be taken from
482− -- PostgreSQL's per-connection
483− -- @default_transaction_isolation@ variable,
484− -- which is initialized according to the
485− -- server's config. The default configuration
486− -- is 'ReadCommitted'.
490− deriving (Show, Eq, Ord, Enum, Bounded)
493− = DefaultReadWriteMode -- ^ the read-write mode will be taken from
494− -- PostgreSQL's per-connection
495− -- @default_transaction_read_only@ variable,
496− -- which is initialized according to the
497− -- server's config. The default configuration
501− deriving (Show, Eq, Ord, Enum, Bounded)
503−data TransactionMode = TransactionMode {
504− isolationLevel :: !IsolationLevel,
505− readWriteMode :: !ReadWriteMode
506− } deriving (Show, Eq)
508−defaultTransactionMode :: TransactionMode
509−defaultTransactionMode = TransactionMode
510− defaultIsolationLevel
511− defaultReadWriteMode
513−defaultIsolationLevel :: IsolationLevel
514−defaultIsolationLevel = DefaultIsolationLevel
516−defaultReadWriteMode :: ReadWriteMode
517−defaultReadWriteMode = DefaultReadWriteMode
519−-- | Execute an action inside a SQL transaction.
521−-- This function initiates a transaction with a \"@begin
522−-- transaction@\" statement, then executes the supplied action. If
523−-- the action succeeds, the transaction will be completed with
524−-- 'Base.commit' before this function returns.
526−-- If the action throws /any/ kind of exception (not just a
527−-- PostgreSQL-related exception), the transaction will be rolled back using
528−-- 'rollback', then the exception will be rethrown.
529−withTransaction :: Connection -> IO a -> IO a
530−withTransaction = withTransactionMode defaultTransactionMode
532−-- | Execute an action inside a SQL transaction with a given isolation level.
533−withTransactionLevel :: IsolationLevel -> Connection -> IO a -> IO a
534−withTransactionLevel lvl
535− = withTransactionMode defaultTransactionMode { isolationLevel = lvl }
537−-- | Execute an action inside a SQL transaction with a given transaction mode.
538−withTransactionMode :: TransactionMode -> Connection -> IO a -> IO a
539−withTransactionMode mode conn act =
540− mask $ \restore -> do
542− r <- restore act `onException` rollback conn
546−-- | Rollback a transaction.
547−rollback :: Connection -> IO ()
548−rollback conn = execute_ conn "ABORT" >> return ()
550−-- | Commit a transaction.
551−commit :: Connection -> IO ()
552−commit conn = execute_ conn "COMMIT" >> return ()
554−-- | Begin a transaction.
555−begin :: Connection -> IO ()
556−begin = beginMode defaultTransactionMode
558−-- | Begin a transaction with a given isolation level
559−beginLevel :: IsolationLevel -> Connection -> IO ()
560−beginLevel lvl = beginMode defaultTransactionMode { isolationLevel = lvl }
562−-- | Begin a transaction with a given transaction mode
563−beginMode :: TransactionMode -> Connection -> IO ()
564−beginMode mode conn = do
565− _ <- execute_ conn $! Query (B.concat ["BEGIN", isolevel, readmode])
568− isolevel = case isolationLevel mode of
569− DefaultIsolationLevel -> ""
570− ReadCommitted -> " ISOLATION LEVEL READ COMMITTED"
571− RepeatableRead -> " ISOLATION LEVEL REPEATABLE READ"
572− Serializable -> " ISOLATION LEVEL SERIALIZABLE"
573− readmode = case readWriteMode mode of
574− DefaultReadWriteMode -> ""
575− ReadWrite -> " READ WRITE"
576− ReadOnly -> " READ ONLY"
578−fmtError :: String -> Query -> [Action] -> a
579−fmtError msg q xs = throw FormatError {
582− , fmtParams = map twiddle xs
584− where twiddle (Plain b) = toByteString b
585− twiddle (Escape s) = s
586− twiddle (EscapeBytea s) = s
587− twiddle (Many ys) = B.concat (map twiddle ys)
@@ -612,9 +658,11 @@ fmtError msg q xs = throw FormatError {
613-- > import Database.PostgreSQL.Simple
659-- > import Database.PostgreSQL.Simple
615-- > hello = do
662-- > hello = do
616−-- > conn <- connect defaultConnectInfo
663+-- > conn <- connectPostgreSQL ""
617−-- > query conn "select 2 + 2"
664+-- > [Only i] <- query_ conn "select 2 + 2"
619-- A 'Query' value does not represent the actual query that will be
667-- A 'Query' value does not represent the actual query that will be
620-- executed, but is a template for constructing the final query.
668-- executed, but is a template for constructing the final query.
@@ -661,7 +709,7 @@ fmtError msg q xs = throw FormatError {
661-- Automated type inference means that you will often be able to avoid
709-- Automated type inference means that you will often be able to avoid
662-- supplying explicit type signatures for the elements of a tuple.
710-- supplying explicit type signatures for the elements of a tuple.
663-- However, sometimes the compiler will not be able to infer your
711-- However, sometimes the compiler will not be able to infer your
664−-- types. Consider a care where you write a numeric literal in a
712+-- types. Consider a case where you write a numeric literal in a
665-- parameter tuple:
713-- parameter tuple:
667-- > query conn "select ? + ?" (40,2)
715-- > query conn "select ? + ?" (40,2)
@@ -675,15 +723,30 @@ fmtError msg q xs = throw FormatError {
675-- The same kind of problem can arise with string literals if you have
723-- The same kind of problem can arise with string literals if you have
676-- the @OverloadedStrings@ language extension enabled. Again, just
724-- the @OverloadedStrings@ language extension enabled. Again, just
677-- use an explicit type signature if this happens.
725-- use an explicit type signature if this happens.
727+-- Finally, remember that the compiler must be able to infer the type
728+-- of a query's /results/ as well as its parameters. We might like
729+-- the following example to work:
731+-- > print =<< query_ conn "select 2 + 2"
733+-- Unfortunately, while a quick glance tells us that the result type
734+-- should be a single row containing a single numeric column, the
735+-- compiler has no way to infer what the types are. We can easily fix
736+-- this by providing an explicit type annotation:
738+-- > xs <- query_ conn "select 2 + 2"
739+-- > print (xs :: [Only Int])
679-- $only_param
741-- $only_param
681-- Haskell lacks a single-element tuple type, so if you have just one
743-- Haskell lacks a single-element tuple type, so if you have just one
682−-- value you want substituted into a query, what should you do?
744+-- value you want substituted into a query or a single-column result,
745+-- what should you do?
684-- The obvious approach would appear to be something like this:
747-- The obvious approach would appear to be something like this:
686−-- > instance (Param a) => QueryParam a where
749+-- > instance (ToField a) => ToRow a where
689-- Unfortunately, this wreaks havoc with type inference, so we take a
752-- Unfortunately, this wreaks havoc with type inference, so we take a
@@ -694,6 +757,9 @@ fmtError msg q xs = throw FormatError {
695-- > execute conn "insert into users (first_name) values (?)"
758-- > execute conn "insert into users (first_name) values (?)"
696-- > ["Nuala"]
759-- > ["Nuala"]
761+-- A row of /n/ query results is represented using an /n/-tuple, so
762+-- you should use 'Only' to represent a single-column result.
@@ -711,7 +777,7 @@ fmtError msg q xs = throw FormatError {
711-- Here's an example:
777-- Here's an example:
713-- > query conn "select * from users where first_name in ?" $
779-- > query conn "select * from users where first_name in ?" $
714−-- > In ["Anna", "Boris", "Carla"]
780+-- > Only $ In ["Anna", "Boris", "Carla"]
716-- If your 'In'-wrapped list is empty, the string @\"(null)\"@ will be
782-- If your 'In'-wrapped list is empty, the string @\"(null)\"@ will be
717-- substituted instead, to ensure that your clause remains
783-- substituted instead, to ensure that your clause remains
@@ -739,7 +805,7 @@ fmtError msg q xs = throw FormatError {
739-- * There must be no other \"@?@\" characters anywhere in your
805-- * There must be no other \"@?@\" characters anywhere in your
740-- template.
806-- template.
742−-- * There must one or more \"@?@\" in the parentheses.
808+-- * There must be one or more \"@?@\" in the parentheses.
744-- * Extra white space is fine.
810-- * Extra white space is fine.
@@ -760,6 +826,22 @@ fmtError msg q xs = throw FormatError {
760-- > insert into users (first_name,last_name) values
826-- > insert into users (first_name,last_name) values
761-- > ('Boris','Karloff'),('Ed','Wood')
827-- > ('Boris','Karloff'),('Ed','Wood')
831+-- PostgreSQL supports returning values from data manipulation statements
832+-- such as @INSERT@ and @UPDATE@. You can use these statements by
833+-- using 'query' instead of 'execute'. For multi-tuple inserts,
834+-- use 'returning' instead of 'executeMany'.
836+-- For example, were there an auto-incrementing @id@ column and
837+-- timestamp column @t@ that defaulted to the present time for the
838+-- @sales@ table, then the following query would insert two new
839+-- sales records and also return their new @id@s and timestamps.
841+-- > let q = "insert into sales (amount, label) values (?,?) returning id, t"
842+-- > xs :: [(Int, UTCTime)] <- query conn q (15,"Sawdust")
843+-- > ys :: [(Int, UTCTime)] <- returning conn q [(20,"Chips"),(300,"Wood")]
763-- $result
845-- $result
765-- The 'query' and 'query_' functions return a list of values in the
847-- The 'query' and 'query_' functions return a list of values in the
@@ -794,7 +876,7 @@ fmtError msg q xs = throw FormatError {
795-- Although SQL can accommodate @NULL@ as a value for any of these
877-- Although SQL can accommodate @NULL@ as a value for any of these
796-- types, Haskell cannot. If your result contains columns that may be
878-- types, Haskell cannot. If your result contains columns that may be
797−-- @NULL@, be sure that you use 'Maybe' in those positions of of your
879+-- @NULL@, be sure that you use 'Maybe' in those positions of your
800-- > (Text, Maybe Int, Int)
882-- > (Text, Maybe Int, Int)
@@ -820,7 +902,7 @@ fmtError msg q xs = throw FormatError {
820-- all values of the given PostgreSQL type is considered \"compatible\".
902-- all values of the given PostgreSQL type is considered \"compatible\".
821-- For instance, you can always extract a PostgreSQL 16-bit @SMALLINT@
903-- For instance, you can always extract a PostgreSQL 16-bit @SMALLINT@
822-- column to a Haskell 'Int'. The Haskell 'Float' type can accurately
904-- column to a Haskell 'Int'. The Haskell 'Float' type can accurately
823−-- represent a @SMALLINT@, so it is considered compatble with those types.
905+-- represent a @SMALLINT@, so it is considered compatible with those types.
825-- * A numeric compatibility check is based only on the type of a
907-- * A numeric compatibility check is based only on the type of a
826-- column, /not/ on its values. For instance, a PostgreSQL 64-bit
908-- column, /not/ on its values. For instance, a PostgreSQL 64-bit
@@ -834,25 +916,3 @@ fmtError msg q xs = throw FormatError {
834-- UTF-8. If you use some other encoding, decoding may fail or give
916-- UTF-8. If you use some other encoding, decoding may fail or give
835-- wrong results. In such cases, write a @newtype@ wrapper and a
917-- wrong results. In such cases, write a @newtype@ wrapper and a
836-- custom 'Result' instance to handle your encoding.
918-- custom 'Result' instance to handle your encoding.
838−getTypename :: Connection -> PQ.Oid -> IO ByteString
839−getTypename conn@Connection{..} oid =
840− case oid2builtin oid of
841− Just builtin -> return $! builtin2typname builtin
842− Nothing -> modifyMVar connectionObjects $ \oidmap -> do
843− case IntMap.lookup (oid2int oid) oidmap of
844− Just name -> return (oidmap, name)
846− names <- query conn "SELECT typname FROM pg_type WHERE oid=?"
848− name <- case names of
849− [] -> return $ throw SqlError {
850− sqlNativeError = -1,
851− sqlErrorMsg = "invalid type oid",
854− [Only x] -> return x
855− _ -> fail "typename query returned more than one result"
856− -- oid is a primary key, so the query should
857− -- never return more than one result
858− return (IntMap.insert (oid2int oid) name oidmap, name)