@@ -1,16 +1,23 @@
1−{-# LANGUAGE BangPatterns, DeriveDataTypeable, OverloadedStrings, DoAndIfThenElse, RecordWildCards, NamedFieldPuns #-}
2−
1+{-# LANGUAGE DeriveDataTypeable #-}
2+{-# LANGUAGE NamedFieldPuns #-}
3+{-# LANGUAGE OverloadedStrings #-}
4+{-# LANGUAGE PatternGuards #-}
5+{-# LANGUAGE RecordWildCards #-}
6+{-# LANGUAGE ViewPatterns #-}
7+
8+------------------------------------------------------------------------------
39-- |
410-- Module: Database.PostgreSQL.Simple
511-- Copyright: (c) 2011 MailRank, Inc.
6−-- (c) 2011 Leon P Smith
12+-- (c) 2011-2012 Leon P Smith
713-- License: BSD3
814-- Maintainer: Leon P Smith <leon@melding-monads.com>
915-- Stability: experimental
10−-- Portability: portable
1116--
12−-- A mid-level client library for the MySQL database, aimed at ease of
17+-- A mid-level client library for the PostgreSQL database, aimed at ease of
1318-- use and high performance.
19+--
20+------------------------------------------------------------------------------
1421
1522module Database.PostgreSQL.Simple
1623 (
@@ -35,6 +42,9 @@ module Database.PostgreSQL.Simple
3542 -- ** Modifying multiple rows at once
3643 -- $many
3744
45+ -- ** @RETURNING@: modifications that return results
46+ -- $returning
47+
3848 -- * Extracting results
3949 -- $result
4050
@@ -45,32 +55,54 @@ module Database.PostgreSQL.Simple
4555 -- $types
4656
4757 -- * Types
48− Base.ConnectInfo(..)
49− , Connection
58+ Connection
5059 , Query
60+ , ToRow
61+ , FromRow
5162 , In(..)
5263 , Binary(..)
5364 , Only(..)
65+ , (:.)(..)
5466 -- ** Exceptions
55− , FormatError(fmtMessage, fmtQuery, fmtParams)
56− , QueryError(qeMessage, qeQuery)
57− , ResultError(errSQLType, errHaskellType, errMessage)
67+ , SomePostgreSqlException(..)
68+ , SqlError(..)
69+ , PQ.ExecStatus(..)
70+ , FormatError(..)
71+ , QueryError(..)
72+ , ResultError(..)
5873 -- * Connection management
59− , Base.connect
6074 , Base.connectPostgreSQL
61− , Base.postgreSQLConnectionString
62− , Base.defaultConnectInfo
6375 , Base.close
76+ , Base.connect
77+ , Base.withConnect
78+ , Base.ConnectInfo(..)
79+ , Base.defaultConnectInfo
80+ , Base.postgreSQLConnectionString
6481 -- * Queries that return results
6582 , query
6683 , query_
67−{--
84+ -- ** Queries taking parser as argument
85+ , queryWith
86+ , queryWith_
6887 -- * Queries that stream results
88+ , FoldOptions(..)
89+ , FetchQuantity(..)
90+ , defaultFoldOptions
6991 , fold
92+ , foldWithOptions
7093 , fold_
94+ , foldWithOptions_
7195 , forEach
7296 , forEach_
73−--}
97+ , returning
98+ -- ** Queries that stream results taking a parser as an argument
99+ , foldWith
100+ , foldWithOptionsAndParser
101+ , foldWith_
102+ , foldWithOptionsAndParser_
103+ , forEachWith
104+ , forEachWith_
105+ , returningWith
74106 -- * Statements that do not return results
75107 , execute
76108 , execute_
@@ -78,6 +110,7 @@ module Database.PostgreSQL.Simple
78110-- , Base.insertID
79111 -- * Transaction handling
80112 , withTransaction
113+ , withSavepoint
81114-- , Base.autocommit
82115 , begin
83116 , commit
@@ -87,55 +120,27 @@ module Database.PostgreSQL.Simple
87120 , formatQuery
88121 ) where
89122
90−import Blaze.ByteString.Builder (Builder, fromByteString, toByteString)
91−import Blaze.ByteString.Builder.Char8 (fromChar)
92−import Control.Applicative ((<$>), pure)
93−import Control.Concurrent.MVar
94−import Control.Exception (Exception, bracket, onException, throw, throwIO)
95−import Control.Monad (forM)
96−import Control.Monad.Fix (fix)
97−import Data.ByteString (ByteString)
98−-- import qualified Data.ByteString as B (unpack)
99−import Data.Char(ord)
100−import Data.Int (Int64)
101−import qualified Data.IntMap as IntMap
102−import Data.List (intersperse)
103−import Data.Monoid (mappend, mconcat)
104−import Data.Typeable (Typeable)
105−--import Database.MySQL.Base (Connection, Result)
106−--import Database.MySQL.Base.Types (Field)
107−import Database.PostgreSQL.Simple.BuiltinTypes (oid2builtin, builtin2typname)
108−import Database.PostgreSQL.Simple.Param (Action(..), inQuotes)
109−import Database.PostgreSQL.Simple.QueryParams (QueryParams(..))
110−import Database.PostgreSQL.Simple.Result (ResultError(..))
111−import Database.PostgreSQL.Simple.QueryResults (QueryResults(..))
112−-- import Database.PostgreSQL.Simple.Result (ResultError(..))
113−import Database.PostgreSQL.Simple.Types (Binary(..), In(..), Only(..), Query(..))
114−import Database.PostgreSQL.Simple.Implementation as Base
123+import Data.ByteString.Builder (Builder, byteString, char8)
124+import Control.Applicative ((<$>))
125+import Control.Exception as E
126+import Data.ByteString (ByteString)
127+import Data.Int (Int64)
128+import Data.List (intersperse)
129+import Data.Monoid (mconcat)
130+import Database.PostgreSQL.Simple.Compat ((<>), toByteString)
131+import Database.PostgreSQL.Simple.Cursor
132+import Database.PostgreSQL.Simple.FromField (ResultError(..))
133+import Database.PostgreSQL.Simple.FromRow (FromRow(..))
134+import Database.PostgreSQL.Simple.ToField (Action(..))
135+import Database.PostgreSQL.Simple.ToRow (ToRow(..))
136+import Database.PostgreSQL.Simple.Types
137+ ( Binary(..), In(..), Only(..), Query(..), (:.)(..) )
138+import Database.PostgreSQL.Simple.Internal as Base
139+import Database.PostgreSQL.Simple.Internal.PQResultUtils
140+import Database.PostgreSQL.Simple.Transaction
115141import qualified Database.PostgreSQL.LibPQ as PQ
116−import Text.Regex.PCRE.Light (compile, caseless, match)
117142import qualified Data.ByteString.Char8 as B
118−--import qualified Database.MySQL.Base as Base
119−
120−-- | Exception thrown if a 'Query' could not be formatted correctly.
121−-- This may occur if the number of \'@?@\' characters in the query
122−-- string does not match the number of parameters provided.
123−data FormatError = FormatError {
124− fmtMessage :: String
125− , fmtQuery :: Query
126− , fmtParams :: [ByteString]
127− } deriving (Eq, Show, Typeable)
128143
129−instance Exception FormatError
130−
131−-- | Exception thrown if 'query' is used to perform an @INSERT@-like
132−-- operation, or 'execute' is used to perform a @SELECT@-like operation.
133−data QueryError = QueryError {
134− qeMessage :: String
135− , qeQuery :: Query
136− } deriving (Eq, Show, Typeable)
137−
138−instance Exception QueryError
139144
140145-- | Format a query string.
141146--
@@ -147,11 +152,11 @@ instance Exception QueryError
147152--
148153-- Throws 'FormatError' if the query string could not be formatted
149154-- correctly.
150−formatQuery :: QueryParams q => Connection -> Query -> q -> IO ByteString
155+formatQuery :: ToRow q => Connection -> Query -> q -> IO ByteString
151156formatQuery conn q@(Query template) qs
152157 | null xs && '?' `B.notElem` template = return template
153158 | otherwise = toByteString <$> buildQuery conn q template xs
154− where xs = renderParams qs
159+ where xs = toRow qs
155160
156161-- | Format a query string with a variable number of rows.
157162--
@@ -166,106 +171,208 @@ formatQuery conn q@(Query template) qs
166171--
167172-- Throws 'FormatError' if the query string could not be formatted
168173-- correctly.
169−formatMany :: (QueryParams q) => Connection -> Query -> [q] -> IO ByteString
174+formatMany :: (ToRow q) => Connection -> Query -> [q] -> IO ByteString
170175formatMany _ q [] = fmtError "no rows supplied" q []
171176formatMany conn q@(Query template) qs = do
172− case match re template [] of
173− Just [_,before,qbits,after] -> do
174− bs <- mapM (buildQuery conn q qbits . renderParams) qs
175− return . toByteString . mconcat $ fromByteString before :
176− intersperse (fromChar ',') bs ++
177− [fromByteString after]
178− _ -> error "foo"
177+ case parseTemplate template of
178+ Just (before, qbits, after) -> do
179+ bs <- mapM (buildQuery conn q qbits . toRow) qs
180+ return . toByteString . mconcat $ byteString before :
181+ intersperse (char8 ',') bs ++
182+ [byteString after]
183+ Nothing -> fmtError "syntax error in multi-row template" q []
184+
185+-- Split the input string into three pieces, @before@, @qbits@, and @after@,
186+-- following this grammar:
187+--
188+-- start: ^ before qbits after $
189+-- before: ([^?]* [^?\w])? 'VALUES' \s*
190+-- qbits: '(' \s* '?' \s* (',' \s* '?' \s*)* ')'
191+-- after: [^?]*
192+--
193+-- \s: [ \t\n\r\f]
194+-- \w: [A-Z] | [a-z] | [\x80-\xFF] | '_' | '$' | [0-9]
195+--
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
179203 where
180− re = compile "^([^?]+\\bvalues\\s*)\
181− \(\\(\\s*[?](?:\\s*,\\s*[?])*\\s*\\))\
182− \([^?]*)$"
183− [caseless]
204+ -- Search for the next occurrence of "VALUES"
205+ search bs =
206+ case B.breakSubstring "VALUES" bs of
207+ (x, y)
208+ -- If "VALUES" is not present in the string, or any '?' characters
209+ -- were encountered prior to it, fail.
210+ | B.null y || ('?' `B.elem` x)
211+ -> Nothing
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
217+
218+ -- Otherwise, we have a legitimate "VALUES" token.
219+ | otherwise
220+ -> parseQueryBits $ skipSpace $ B.drop 6 y
221+
222+ -- Parse '(' \s* '?' \s* . If this doesn't match
223+ -- (and we don't consume a '?'), look for another "VALUES".
224+ --
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.
228+ parseQueryBits qb
229+ | Just ('(', skipSpace -> bs1) <- B.uncons qb
230+ , Just ('?', skipSpace -> bs2) <- B.uncons bs1
231+ = finishQueryBits qb bs2
232+ | otherwise
233+ = search qb
234+
235+ -- Parse (',' \s* '?' \s*)* ')' [^?]* .
236+ --
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
243+ then Nothing
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
248+ | otherwise
249+ = Nothing
250+
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.
254+ --
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 =
258+ (s1, s2, source'')
259+ where
260+ (s1, source') = B.splitAt (B.length source - B.length p1) source
261+ (s2, source'') = B.splitAt (B.length p1 - B.length p2) source'
262+
263+ toUpper_ascii c | c >= 'a' && c <= 'z' = toEnum (fromEnum c - 32)
264+ | otherwise = c
265+
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')
272+ || c == '_'
273+ || c == '$'
274+
275+ -- Based on {space} in scan.l
276+ isSpace_ascii c = (c == ' ') || (c >= '\t' && c <= '\r')
277+
278+ skipSpace = B.dropWhile isSpace_ascii
184279
185−escapeStringConn conn s = withConnection conn $ \c -> do
186− PQ.escapeStringConn c s
187280
188281buildQuery :: Connection -> Query -> ByteString -> [Action] -> IO Builder
189−buildQuery conn q template xs = zipParams (split template) <$> mapM sub xs
190− where quote = inQuotes . fromByteString . maybe undefined id
191− sub (Plain b) = pure b
192− sub (Escape s) = quote <$> escapeStringConn conn s
193− sub (Many ys) = mconcat <$> mapM sub ys
194− split s = fromByteString h : if B.null t then [] else split (B.tail t)
195− where (h,t) = B.break (=='?') s
196− zipParams (t:ts) (p:ps) = t `mappend` p `mappend` zipParams ts ps
282+buildQuery conn q template xs =
283+ zipParams (split template) <$> mapM (buildAction conn q xs) xs
284+ where split s =
285+ -- This part escapes double '??'s to make literal '?'s possible
286+ -- in PostgreSQL queries using the JSON operators: @?@, @?|@ and @?&@
287+ let (h,t) = breakOnSingleQuestionMark s
288+ in byteString h
289+ : if B.null t
290+ then []
291+ else split (B.tail t)
292+ zipParams (t:ts) (p:ps) = t <> p <> zipParams ts ps
197293 zipParams [t] [] = t
198− zipParams _ _ = fmtError (show (B.count '?' template) ++
199− " '?' characters, but " ++
294+ zipParams _ _ = fmtError (show countSingleQs ++
295+ " single '?' characters, but " ++
200296 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
302+ _ -> i
303+ where qms = B.splitAt 1 qmBS
304+ (qmBS,nextQMBS) = B.splitAt 2 qmBS'
305+ qmBS' = B.dropWhile (/= '?') bs
201306
202307-- | Execute an @INSERT@, @UPDATE@, or other SQL query that is not
203308-- expected to return results.
204309--
205310-- Returns the number of rows affected.
206311--
207−-- Throws 'FormatError' if the query could not be formatted correctly.
208−execute :: (QueryParams q) => Connection -> Query -> q -> IO Int64
312+-- Throws 'FormatError' if the query could not be formatted correctly, or
313+-- a 'SqlError' exception if the backend returns an error.
314+execute :: (ToRow q) => Connection -> Query -> q -> IO Int64
209315execute conn template qs = do
210316 result <- exec conn =<< formatQuery conn template qs
211317 finishExecute conn template result
212318
213−-- | A version of 'execute' that does not perform query substitution.
214−execute_ :: Connection -> Query -> IO Int64
215−execute_ conn q@(Query stmt) = do
216− result <- exec conn stmt
217− finishExecute conn q result
218−
219319-- | Execute a multi-row @INSERT@, @UPDATE@, or other SQL query that is not
220320-- expected to return results.
221321--
222−-- 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.
223325--
224−-- Throws 'FormatError' if the query could not be formatted correctly.
225−executeMany :: (QueryParams q) => Connection -> Query -> [q] -> IO Int64
326+-- Throws 'FormatError' if the query could not be formatted correctly, or
327+-- a 'SqlError' exception if the backend returns an error.
328+--
329+-- For example, here's a command that inserts two rows into a table
330+-- with two columns:
331+--
332+-- @
333+-- executeMany c [sql|
334+-- INSERT INTO sometable VALUES (?,?)
335+-- |] [(1, \"hello\"),(2, \"world\")]
336+-- @
337+--
338+-- Here's an canonical example of a multi-row update command:
339+--
340+-- @
341+-- executeMany c [sql|
342+-- UPDATE sometable
343+-- SET y = upd.y
344+-- FROM (VALUES (?,?)) as upd(x,y)
345+-- WHERE sometable.x = upd.x
346+-- |] [(1, \"hello\"),(2, \"world\")]
347+-- @
348+
349+executeMany :: (ToRow q) => Connection -> Query -> [q] -> IO Int64
226350executeMany _ _ [] = return 0
227351executeMany conn q qs = do
228352 result <- exec conn =<< formatMany conn q qs
229353 finishExecute conn q result
230354
231−finishExecute :: Connection -> Query -> PQ.Result -> IO Int64
232−finishExecute conn q result = do
233− status <- PQ.resultStatus result
234− case status of
235− PQ.EmptyQuery -> fail "empty query" -- FIXME: error message
236− PQ.CommandOk -> do
237− ncols <- PQ.nfields result
238− if ncols /= 0
239− then throwIO $ QueryError ("execute resulted in " ++ show ncols ++
240− "-column result") q
241− else do
242− nstr <- PQ.cmdTuples result
243− return $ case nstr of
244− Nothing -> 0 -- is this appropriate?
245− Just str -> toInteger str
246− PQ.TuplesOk -> do
247− ncols <- PQ.nfields result
248− throwIO $ QueryError ("execute resulted in " ++ show ncols ++
249− "-column result") q
250− PQ.CopyIn -> fail "FIXME: postgresql-simple does not currently support COPY IN"
251− PQ.CopyOut -> fail "FIXME: postgresql-simple does not currently support COPY OUT"
252− _ -> do
253− errormsg <- maybe "" id <$> PQ.resultErrorMessage result
254− statusmsg <- PQ.resStatus status
255− state <- maybe "" id <$> PQ.resultErrorField result PQ.DiagSqlstate
256− throw $ SqlError { sqlState = state
257− , sqlNativeError = 0 -- FIXME
258− , sqlErrorMsg = B.concat [ "execute: ", statusmsg
259− , ": ", errormsg ]}
260− where
261− toInteger str = B.foldl' delta 0 str
262− where
263− delta acc c =
264− if '0' <= c && c <= '9'
265− then 10 * acc + fromIntegral (ord c - ord '0')
266− else error ("finishExecute: not an int: " ++ B.unpack str)
267−
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'.
361+--
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.
365+--
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
268369
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
269376
270377-- | Perform a @SELECT@ or other SQL query that is expected to return
271378-- results. All results are retrieved and converted before this
@@ -282,33 +389,44 @@ finishExecute conn q result = do
282389-- using 'execute' instead of 'query').
283390--
284391-- * 'ResultError': result conversion failed.
285−query :: (QueryParams q, QueryResults r)
286− => Connection -> Query -> q -> IO [r]
287−query conn template qs = do
288− result <- exec conn =<< formatQuery conn template qs
289− finishQuery conn template result
392+--
393+-- * 'SqlError': the postgresql backend returned an error, e.g.
394+-- a syntax or type error, or an incorrect table or column name.
395+query :: (ToRow q, FromRow r) => Connection -> Query -> q -> IO [r]
396+query = queryWith fromRow
290397
291398-- | A version of 'query' that does not perform query substitution.
292−query_ :: (QueryResults r) => Connection -> Query -> IO [r]
293−query_ conn q@(Query que) = do
399+query_ :: (FromRow r) => Connection -> Query -> IO [r]
400+query_ = queryWith_ fromRow
401+
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
407+
408+-- | A version of 'query_' taking parser as argument
409+queryWith_ :: RowParser r -> Connection -> Query -> IO [r]
410+queryWith_ parser conn q@(Query que) = do
294411 result <- exec conn que
295− finishQuery conn q result
296−{--
412+ finishQueryWith parser conn q result
413+
297414-- | Perform a @SELECT@ or other SQL query that is expected to return
298415-- results. Results are streamed incrementally from the server, and
299416-- consumed via a left fold.
300417--
301−-- The result consumer must be carefully written to execute
302−-- quickly. If the consumer is slow, server resources will be tied up,
303−-- and other clients may not be able to update the tables from which
304−-- the results are being streamed.
305−--
306418-- When dealing with small results, it may be simpler (and perhaps
307419-- faster) to use 'query' instead.
308420--
309421-- This fold is /not/ strict. The stream consumer is responsible for
310422-- forcing the evaluation of its result to avoid space leaks.
311423--
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.
429+--
312430-- Exceptions that may be thrown:
313431--
314432-- * 'FormatError': the query string could not be formatted correctly.
@@ -317,164 +435,202 @@ query_ conn q@(Query que) = do
317435-- using 'execute' instead of 'query').
318436--
319437-- * 'ResultError': result conversion failed.
320−fold :: (QueryParams q, QueryResults r) =>
321− Connection
322− -> Query -- ^ Query template.
323− -> q -- ^ Query parameters.
324− -> a -- ^ Initial state for result consumer.
325− -> (a -> r -> IO a) -- ^ Result consumer.
326− -> IO a
327−fold conn template qs z f = do
328− Base.query conn =<< formatQuery conn template qs
329− finishFold conn template z f
330−--}
331−{--
438+--
439+-- * 'SqlError': the postgresql backend returned an error, e.g.
440+-- a syntax or type error, or an incorrect table or column name.
441+fold :: ( FromRow row, ToRow params )
442+ => Connection
443+ -> Query
444+ -> params
445+ -> a
446+ -> (a -> row -> IO a)
447+ -> IO a
448+fold = foldWithOptions defaultFoldOptions
449+
450+-- | A version of 'fold' taking a parser as an argument
451+foldWith :: ( ToRow params )
452+ => RowParser row
453+ -> Connection
454+ -> Query
455+ -> params
456+ -> a
457+ -> (a -> row -> IO a)
458+ -> IO a
459+foldWith = foldWithOptionsAndParser defaultFoldOptions
460+
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.
464+data FetchQuantity
465+ = Automatic
466+ | Fixed !Int
467+
468+data FoldOptions
469+ = FoldOptions {
470+ fetchQuantity :: !FetchQuantity,
471+ transactionMode :: !TransactionMode
472+ }
473+
474+-- | defaults to 'Automatic', and 'TransactionMode' 'ReadCommitted' 'ReadOnly'
475+defaultFoldOptions :: FoldOptions
476+defaultFoldOptions = FoldOptions {
477+ fetchQuantity = Automatic,
478+ transactionMode = TransactionMode ReadCommitted ReadOnly
479+ }
480+
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.
487+foldWithOptions :: ( FromRow row, ToRow params )
488+ => FoldOptions
489+ -> Connection
490+ -> Query
491+ -> params
492+ -> a
493+ -> (a -> row -> IO a)
494+ -> IO a
495+foldWithOptions opts = foldWithOptionsAndParser opts fromRow
496+
497+-- | A version of 'foldWithOptions' taking a parser as an argument
498+foldWithOptionsAndParser :: (ToRow params)
499+ => FoldOptions
500+ -> RowParser row
501+ -> Connection
502+ -> Query
503+ -> params
504+ -> a
505+ -> (a -> row -> IO a)
506+ -> IO a
507+foldWithOptionsAndParser opts parser conn template qs a f = do
508+ q <- formatQuery conn template qs
509+ doFold opts parser conn template (Query q) a f
510+
332511-- | A version of 'fold' that does not perform query substitution.
333−fold_ :: (QueryResults r) =>
512+fold_ :: (FromRow r) =>
334513 Connection
335514 -> Query -- ^ Query.
336515 -> a -- ^ Initial state for result consumer.
337516 -> (a -> r -> IO a) -- ^ Result consumer.
338517 -> IO a
339−fold_ conn q@(Query que) z f = do
340− Base.query conn que
341− finishFold conn q z f
342−--}
343−{--
518+fold_ = foldWithOptions_ defaultFoldOptions
519+
520+-- | A version of 'fold_' taking a parser as an argument
521+foldWith_ :: RowParser r
522+ -> Connection
523+ -> Query
524+ -> a
525+ -> (a -> r -> IO a)
526+ -> IO a
527+foldWith_ = foldWithOptionsAndParser_ defaultFoldOptions
528+
529+foldWithOptions_ :: (FromRow r) =>
530+ FoldOptions
531+ -> Connection
532+ -> Query -- ^ Query.
533+ -> a -- ^ Initial state for result consumer.
534+ -> (a -> r -> IO a) -- ^ Result consumer.
535+ -> IO a
536+foldWithOptions_ opts conn query' a f = doFold opts fromRow conn query' query' a f
537+
538+-- | A version of 'foldWithOptions_' taking a parser as an argument
539+foldWithOptionsAndParser_ :: FoldOptions
540+ -> RowParser r
541+ -> Connection
542+ -> Query -- ^ Query.
543+ -> a -- ^ Initial state for result consumer.
544+ -> (a -> r -> IO a) -- ^ Result consumer.
545+ -> IO a
546+foldWithOptionsAndParser_ opts parser conn query' a f = doFold opts parser conn query' query' a f
547+
548+doFold :: FoldOptions
549+ -> RowParser row
550+ -> Connection
551+ -> Query
552+ -> Query
553+ -> a
554+ -> (a -> row -> IO a)
555+ -> IO a
556+doFold FoldOptions{..} parser conn _template q a0 f = do
557+ stat <- withConnection conn PQ.transactionStatus
558+ case stat of
559+ PQ.TransIdle -> withTransactionMode transactionMode conn go
560+ PQ.TransInTrans -> go
561+ PQ.TransActive -> fail "foldWithOpts FIXME: PQ.TransActive"
562+ -- This _shouldn't_ occur in the current incarnation of
563+ -- the library, as we aren't using libpq asynchronously.
564+ -- However, it could occur in future incarnations of
565+ -- this library or if client code uses the Internal module
566+ -- to use raw libpq commands on postgresql-simple connections.
567+ PQ.TransInError -> fail "foldWithOpts FIXME: PQ.TransInError"
568+ -- This should be turned into a better error message.
569+ -- It is probably a bad idea to automatically roll
570+ -- back the transaction and start another.
571+ PQ.TransUnknown -> fail "foldWithOpts FIXME: PQ.TransUnknown"
572+ -- Not sure what this means.
573+ where
574+ declare =
575+ declareCursor conn q
576+ fetch cursor a =
577+ foldForwardWithParser cursor parser chunkSize f a
578+
579+ go = bracket declare closeCursor $ \cursor ->
580+ let loop a = fetch cursor a >>=
581+ \r -> case r of
582+ Left x -> return x
583+ Right x -> loop x
584+ in loop a0
585+
586+-- FIXME: choose the Automatic chunkSize more intelligently
587+-- One possibility is to use the type of the results, although this
588+-- still isn't a perfect solution, given that common types (e.g. text)
589+-- are of highly variable size.
590+-- A refinement of this technique is to pick this number adaptively
591+-- as results are read in from the database.
592+ chunkSize = case fetchQuantity of
593+ Automatic -> 256
594+ Fixed n -> n
595+
344596-- | A version of 'fold' that does not transform a state value.
345−forEach :: (QueryParams q, QueryResults r) =>
597+forEach :: (ToRow q, FromRow r) =>
346598 Connection
347599 -> Query -- ^ Query template.
348600 -> q -- ^ Query parameters.
349601 -> (r -> IO ()) -- ^ Result consumer.
350602 -> IO ()
351−forEach conn template qs = fold conn template qs () . const
603+forEach = forEachWith fromRow
352604{-# INLINE forEach #-}
353605
606+-- | A version of 'forEach' taking a parser as an argument
607+forEachWith :: ( ToRow q )
608+ => RowParser r
609+ -> Connection
610+ -> Query
611+ -> q
612+ -> (r -> IO ())
613+ -> IO ()
614+forEachWith parser conn template qs = foldWith parser conn template qs () . const
615+{-# INLINE forEachWith #-}
616+
354617-- | A version of 'forEach' that does not perform query substitution.
355−forEach_ :: (QueryResults r) =>
618+forEach_ :: (FromRow r) =>
356619 Connection
357620 -> Query -- ^ Query template.
358621 -> (r -> IO ()) -- ^ Result consumer.
359622 -> IO ()
360−forEach_ conn template = fold_ conn template () . const
623+forEach_ = forEachWith_ fromRow
361624{-# INLINE forEach_ #-}
362−--}
363625
364−forM' :: (Ord n, Num n) => n -> n -> (n -> IO a) -> IO [a]
365−forM' lo hi m = loop hi []
366− where
367− loop !n !as
368− | n < lo = return as
369− | otherwise = do
370− a <- m n
371− loop (n-1) (a:as)
372−
373−finishQuery :: (QueryResults r) => Connection -> Query -> PQ.Result -> IO [r]
374−finishQuery conn q result = do
375− status <- PQ.resultStatus result
376− case status of
377− PQ.EmptyQuery -> fail "empty query" -- FIXME: error message
378− PQ.CommandOk -> do
379− throwIO $ QueryError "query resulted in a command response" q
380− PQ.TuplesOk -> do
381− ncols <- PQ.nfields result
382− fields <- forM' 0 (ncols-1) $ \column -> do
383− type_oid <- PQ.ftype result column
384− typename <- getTypename conn type_oid
385− return Field{..}
386− nrows <- PQ.ntuples result
387− forM' 0 (nrows-1) $ \row -> do
388− values <- forM' 0 (ncols-1) (\col -> PQ.getvalue' result row col)
389− case convertResults fields values of
390− Fail err -> throwIO err
391− Success a -> return a
392− PQ.CopyIn -> fail "FIXME: postgresql-simple does not currently support COPY IN"
393− PQ.CopyOut -> fail "FIXME: postgresql-simple does not currently support COPY OUT"
394− _ -> do
395− errormsg <- maybe "" id <$> PQ.resultErrorMessage result
396− statusmsg <- PQ.resStatus status
397− state <- maybe "" id <$> PQ.resultErrorField result PQ.DiagSqlstate
398− throw $ SqlError { sqlState = state
399− , sqlNativeError = 0 -- FIXME
400− , sqlErrorMsg = B.concat [ "execute: ", statusmsg
401− , ": ", errormsg ]}
402−
403−{--
404−withResult (Base.storeResult conn) q $ \r fs -> do
405− status <-
406−/ flip fix [] $ \loop acc -> do
407− row <- Base.fetchRow r
408− case row of
409− [] -> return (reverse acc)
410− _ -> let !c = convertResults fs row
411− in loop (c:acc)
412−--}
413−{--
414−finishFold :: (QueryResults r) =>
415− Connection -> Query -> a -> (a -> r -> IO a) -> IO a
416−finishFold conn q z0 f = withResult (Base.useResult conn) q $ \r fs ->
417− flip fix z0 $ \loop z -> do
418− row <- Base.fetchRow r
419− case row of
420− [] -> return z
421− _ -> (f z $! convertResults fs row) >>= loop
422−--}
423−{--
424−withResult :: (IO Result) -> Query -> (Result -> [Field] -> IO a) -> IO a
425−withResult fetchResult q act = bracket fetchResult Base.freeResult $ \r -> do
426− ncols <- Base.fieldCount (Right r)
427− if ncols == 0
428− then throwIO $ QueryError "query resulted in zero-column result" q
429− else act r =<< Base.fetchFields r
430−--}
431−-- | Execute an action inside a SQL transaction.
432−--
433−-- This function initiates a transaction with a \"@begin
434−-- transaction@\" statement, then executes the supplied action. If
435−-- the action succeeds, the transaction will be completed with
436−-- 'Base.commit' before this function returns.
437−--
438−-- If the action throws /any/ kind of exception (not just a
439−-- MySQL-related exception), the transaction will be rolled back using
440−-- 'Base.rollback', then the exception will be rethrown.
441−withTransaction :: Connection -> IO a -> IO a
442−withTransaction conn act = do
443− _ <- begin conn
444− r <- act `onException` rollback conn
445− commit conn
446− return r
447−
448−-- | Rollback a transaction.
449−-- rollback :: (MonadCatchIO m,MonadIO m) => Connection -> m ()
450−rollback :: Connection -> IO ()
451−rollback conn = do
452− _ <- execute_ conn "ABORT;"
453− return ()
454−
455−-- | Commit a transaction.
456−-- commit :: (MonadCatchIO m,MonadIO m) => Connection -> m ()
457−commit :: Connection -> IO ()
458−commit conn = do
459− _ <- execute_ conn "COMMIT;"
460− return ()
461−
462−-- | Begin a transaction.
463−-- begin :: (MonadCatchIO m,MonadIO m) => Connection -> m ()
464−begin :: Connection -> IO ()
465−begin conn = do
466− _ <- execute_ conn "BEGIN;"
467− return ()
468−
469−fmtError :: String -> Query -> [Action] -> a
470−fmtError msg q xs = throw FormatError {
471− fmtMessage = msg
472− , fmtQuery = q
473− , fmtParams = map twiddle xs
474− }
475− where twiddle (Plain b) = toByteString b
476− twiddle (Escape s) = s
477− twiddle (Many ys) = B.concat (map twiddle ys)
626+forEachWith_ :: RowParser r
627+ -> Connection
628+ -> Query
629+ -> (r -> IO ())
630+ -> IO ()
631+forEachWith_ parser conn template = foldWith_ parser conn template () . const
632+{-# INLINE forEachWith_ #-}
633+
478634
479635-- $use
480636--
@@ -500,11 +656,13 @@ fmtError msg q xs = throw FormatError {
500656--
501657-- > {-# LANGUAGE OverloadedStrings #-}
502658-- >
503−-- > import Database.MySQL.Simple
659+-- > import Database.PostgreSQL.Simple
504660-- >
661+-- > hello :: IO Int
505662-- > hello = do
506−-- > conn <- connect defaultConnectInfo
507−-- > query conn "select 2 + 2"
663+-- > conn <- connectPostgreSQL ""
664+-- > [Only i] <- query_ conn "select 2 + 2"
665+-- > return i
508666--
509667-- A 'Query' value does not represent the actual query that will be
510668-- executed, but is a template for constructing the final query.
@@ -551,7 +709,7 @@ fmtError msg q xs = throw FormatError {
551709-- Automated type inference means that you will often be able to avoid
552710-- supplying explicit type signatures for the elements of a tuple.
553711-- However, sometimes the compiler will not be able to infer your
554−-- 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
555713-- parameter tuple:
556714--
557715-- > query conn "select ? + ?" (40,2)
@@ -565,15 +723,30 @@ fmtError msg q xs = throw FormatError {
565723-- The same kind of problem can arise with string literals if you have
566724-- the @OverloadedStrings@ language extension enabled. Again, just
567725-- use an explicit type signature if this happens.
726+--
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:
730+--
731+-- > print =<< query_ conn "select 2 + 2"
732+--
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:
737+--
738+-- > xs <- query_ conn "select 2 + 2"
739+-- > print (xs :: [Only Int])
568740
569741-- $only_param
570742--
571743-- Haskell lacks a single-element tuple type, so if you have just one
572−-- 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?
573746--
574747-- The obvious approach would appear to be something like this:
575748--
576−-- > instance (Param a) => QueryParam a where
749+-- > instance (ToField a) => ToRow a where
577750-- > ...
578751--
579752-- Unfortunately, this wreaks havoc with type inference, so we take a
@@ -584,6 +757,9 @@ fmtError msg q xs = throw FormatError {
584757--
585758-- > execute conn "insert into users (first_name) values (?)"
586759-- > ["Nuala"]
760+--
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.
587763
588764-- $in
589765--
@@ -601,7 +777,7 @@ fmtError msg q xs = throw FormatError {
601777-- Here's an example:
602778--
603779-- > query conn "select * from users where first_name in ?" $
604−-- > In ["Anna", "Boris", "Carla"]
780+-- > Only $ In ["Anna", "Boris", "Carla"]
605781--
606782-- If your 'In'-wrapped list is empty, the string @\"(null)\"@ will be
607783-- substituted instead, to ensure that your clause remains
@@ -629,7 +805,7 @@ fmtError msg q xs = throw FormatError {
629805-- * There must be no other \"@?@\" characters anywhere in your
630806-- template.
631807--
632−-- * There must one or more \"@?@\" in the parentheses.
808+-- * There must be one or more \"@?@\" in the parentheses.
633809--
634810-- * Extra white space is fine.
635811--
@@ -650,10 +826,26 @@ fmtError msg q xs = throw FormatError {
650826-- > insert into users (first_name,last_name) values
651827-- > ('Boris','Karloff'),('Ed','Wood')
652828
829+-- $returning
830+--
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'.
835+--
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.
840+--
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")]
844+
653845-- $result
654846--
655847-- The 'query' and 'query_' functions return a list of values in the
656−-- 'QueryResults' typeclass. This class performs automatic extraction
848+-- 'FromRow' typeclass. This class performs automatic extraction
657849-- and type conversion of rows from a query result.
658850--
659851-- Here is a simple example of how to extract results:
@@ -684,7 +876,7 @@ fmtError msg q xs = throw FormatError {
684876--
685877-- Although SQL can accommodate @NULL@ as a value for any of these
686878-- types, Haskell cannot. If your result contains columns that may be
687−-- @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
688880-- tuple.
689881--
690882-- > (Text, Maybe Int, Int)
@@ -707,16 +899,15 @@ fmtError msg q xs = throw FormatError {
707899-- permissive. Here are the rules.
708900--
709901-- * For numeric types, any Haskell type that can accurately represent
710−-- all values of the given MySQL type is considered \"compatible\".
711−-- For instance, you can always extract a MySQL @TINYINT@ column to
712−-- a Haskell 'Int'. The Haskell 'Float' type can accurately
713−-- represent MySQL integer types of size up to @INT24@, so it is
714−-- considered compatble with those types.
902+-- all values of the given PostgreSQL type is considered \"compatible\".
903+-- For instance, you can always extract a PostgreSQL 16-bit @SMALLINT@
904+-- column to a Haskell 'Int'. The Haskell 'Float' type can accurately
905+-- represent a @SMALLINT@, so it is considered compatible with those types.
715906--
716907-- * A numeric compatibility check is based only on the type of a
717−-- column, /not/ on its values. For instance, a MySQL @LONG_LONG@
718−-- column will be considered incompatible with a Haskell 'Int8',
719−-- even if it contains the value @1@.
908+-- column, /not/ on its values. For instance, a PostgreSQL 64-bit
909+-- @BIGINT@ column will be considered incompatible with a Haskell
910+-- 'Int16', even if it contains the value @1@.
720911--
721912-- * If a numeric incompatibility is found, 'query' will throw a
722913-- 'ResultError'.
@@ -725,29 +916,3 @@ fmtError msg q xs = throw FormatError {
725916-- UTF-8. If you use some other encoding, decoding may fail or give
726917-- wrong results. In such cases, write a @newtype@ wrapper and a
727918-- custom 'Result' instance to handle your encoding.
728−
729−getTypename :: Connection -> PQ.Oid -> IO ByteString
730−getTypename conn@Connection{..} oid =
731− case oid2builtin oid of
732− Just builtin -> return $! builtin2typname builtin
733− Nothing -> do
734− oidmap <- takeMVar connectionObjects
735− case IntMap.lookup (oid2int oid) oidmap of
736− Just name -> putMVar connectionObjects oidmap >> return name
737− Nothing -> do
738− names <- query conn "SELECT typname FROM pg_type WHERE oid=?"
739− (Only oid)
740− name <- case names of
741− [] -> return $ throw SqlError {
742− sqlNativeError = -1,
743− sqlErrorMsg = "invalid type oid",
744− sqlState = ""
745− }
746− [Only x] -> return x
747− _ -> fail "typename query returned more than one result"
748− -- oid is a primary key, so the query should
749− -- never return more than one result
750− putMVar connectionObjects (IntMap.insert (oid2int oid) name oidmap)
751− return name
752− `onException` do
753− putMVar connectionObjects oidmap