sqlite-simple-0.4.15.0: Mid-Level SQLite client library

Copyright(c) 2011 MailRank Inc.
(c) 2011-2012 Leon P Smith
(c) 2012-2013 Janne Hellsten
LicenseBSD3
MaintainerJanne Hellsten <jjhellst@gmail.com>
Portabilityportable
Safe HaskellNone
LanguageHaskell2010

Database.SQLite.Simple

Contents

Description

 

Synopsis

Examples of use

An example that creates a table test, inserts a couple of rows and proceeds to showcase how to update or delete rows. This example also demonstrates the use of lastInsertRowId (how to refer to a previously inserted row) and executeNamed (an easier to maintain form of query parameter naming).

{-# LANGUAGE OverloadedStrings #-}

import           Control.Applicative
import qualified Data.Text as T
import           Database.SQLite.Simple
import           Database.SQLite.Simple.FromRow

data TestField = TestField Int T.Text deriving (Show)

instance FromRow TestField where
  fromRow = TestField <$> field <*> field

instance ToRow TestField where
  toRow (TestField id_ str) = toRow (id_, str)

main :: IO ()
main = do
  conn <- open "test.db"
  execute_ conn "CREATE TABLE IF NOT EXISTS test (id INTEGER PRIMARY KEY, str TEXT)"
  execute conn "INSERT INTO test (str) VALUES (?)" (Only ("test string 2" :: String))
  execute conn "INSERT INTO test (id, str) VALUES (?,?)" (TestField 13 "test string 3")
  rowId <- lastInsertRowId conn
  executeNamed conn "UPDATE test SET str = :str WHERE id = :id" [":str" := ("updated str" :: T.Text), ":id" := rowId]
  r <- query_ conn "SELECT * from test" :: IO [TestField]
  mapM_ print r
  execute conn "DELETE FROM test WHERE id = ?" (Only rowId)
  close conn

The Query type

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. A Query is a newtype-wrapped Text. It intentionally exposes a tiny API that is not compatible with the Text 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.SQLite.Simple

hello = do
  conn <- open "test.db"
  [[x]] <- query_ conn "select 2 + 2"
  print x

A Query value does not represent the actual query that will be executed, but is a template for constructing the final query.

Parameter substitution

Since applications need to be able to construct queries with parameters that change, this library uses SQLite's parameter binding query substitution capability.

This library restricts parameter substitution to work only with named parameters and positional arguments with the "?" syntax. The API does not support for mixing these two types of bindings. Unsupported parameters will be rejected and a FormatError will be thrown.

You should always use parameter substitution instead of inlining your dynamic parameters into your queries with messy string concatenation. SQLite will automatically quote and escape your data into these placeholder parameters; this defeats the single most common injection vector for malicious data.

Positional parameters

The Query template accepted by query, execute and fold can contain any number of "?" characters. Both query and execute accept a third argument, typically a tuple. When the query executes, the first "?" in the template will be replaced with the first element of the tuple, the second "?" with the second element, and so on. This substitution happens inside the native SQLite implementation.

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.

Named parameters

Named parameters are accepted by queryNamed, executeNamed and foldNamed. These functions take a list of NamedParams which are key-value pairs binding a value to an argument name. As is the case with "?" parameters, named parameters are automatically escaped by the SQLite library. The parameter names are prefixed with either : or @, e.g. :foo or @foo.

Example:

r <- queryNamed c "SELECT id,text FROM posts WHERE id = :id AND date >= :date" [":id" := postId, ":date" := afterDate]

Note that you can mix different value types in the same list. E.g., the following is perfectly legal:

[":id" := (3 :: Int), ":str" := ("foo" :: String)]

The parameter name (or key) in the NamedParam must match exactly the name written in the SQL query. E.g., if you used :foo in your SQL statement, you need to use ":foo" as the parameter key, not "foo". Some libraries like Python's sqlite3 automatically drop the : character from the name.

Type 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 case 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.

Substituting a single parameter

Haskell lacks a single-element tuple type, so if you have just one value you want substituted into a query, what should you do?

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"]

Or you can use named parameters which do not have this restriction.

Extracting results

The query and query_ functions return a list of values in the FromRow 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 T

xs <- query_ conn "select name,age from users"
forM_ xs $ \(name,age) ->
  putStrLn $ T.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.

Handling null values

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.

Type conversions

Conversion of SQL values to Haskell values is somewhat permissive. Here are the rules.

  • For numeric types, any Haskell type that can accurately represent an SQLite INTEGER is considered "compatible".
  • If a numeric incompatibility is found, query will throw a ResultError.
  • SQLite's TEXT type is always encoded in UTF-8. Thus any text data coming from an SQLite database should always be compatible with Haskell String and Text types.
  • SQLite's BLOB type will only be conversible to a Haskell ByteString.

You can extend conversion support to your own types be adding your own FromField / ToField instances.

Conversion to/from UTCTime

SQLite's datetime allows for multiple string representations of UTC time. The following formats are supported for reading SQLite times into Haskell UTCTime values:

  • YYYY-MM-DD HH:MM
  • YYYY-MM-DD HH:MM:SS
  • YYYY-MM-DD HH:MM:SS.SSS
  • YYYY-MM-DDTHH:MM
  • YYYY-MM-DDTHH:MM:SS
  • YYYY-MM-DDTHH:MM:SS.SSS

The above may also be optionally followed by a timezone indicator of the form "[+-]HH:MM" or just "Z".

When Haskell UTCTime values are converted into SQLite values (e.g., parameters for a query), the following format is used:

  • YYYY-MM-DD HH:MM:SS.SSS

The last ".SSS" subsecond part is dropped if it's zero. No timezone indicator is used when converting from a UTCTime value into an SQLite string. SQLite assumes all datetimes are in UTC time.

The parser and printers are implemented in Database.SQLite.Simple.Time.

Read more about SQLite's time strings in http://sqlite.org/lang_datefunc.html

newtype Query Source #

A query string. This type is intended to make it difficult to construct a SQL query by concatenating string fragments, as that is an extremely common way to accidentally introduce SQL injection vulnerabilities into an application.

This type is an instance of IsString, so the easiest way to construct a query is to enable the OverloadedStrings language extension and then simply write the query in double quotes.

{-# LANGUAGE OverloadedStrings #-}

import Database.SQLite.Simple

q :: Query
q = "select ?"

The underlying type is a Text, and literal Haskell strings that contain Unicode characters will be correctly transformed to UTF-8.

Constructors

Query 

Fields

newtype Connection Source #

Connection to an open database.

You can use connectionHandle to gain access to the underlying http://hackage.haskell.org/package/direct-sqlite connection. This may be useful if you need to access some direct-sqlite functionality that's not exposed in the sqlite-simple API. This should be a safe thing to do although mixing both APIs is discouraged.

Constructors

Connection 

class ToRow a where Source #

A collection type that can be turned into a list of SQLData elements.

Minimal complete definition

toRow

Methods

toRow :: a -> [SQLData] Source #

ToField a collection of values.

Instances

ToRow () Source # 

Methods

toRow :: () -> [SQLData] Source #

ToField a => ToRow [a] Source # 

Methods

toRow :: [a] -> [SQLData] Source #

ToField a => ToRow (Only a) Source # 

Methods

toRow :: Only a -> [SQLData] Source #

(ToField a, ToField b) => ToRow (a, b) Source # 

Methods

toRow :: (a, b) -> [SQLData] Source #

(ToRow a, ToRow b) => ToRow ((:.) a b) Source # 

Methods

toRow :: (a :. b) -> [SQLData] Source #

(ToField a, ToField b, ToField c) => ToRow (a, b, c) Source # 

Methods

toRow :: (a, b, c) -> [SQLData] Source #

(ToField a, ToField b, ToField c, ToField d) => ToRow (a, b, c, d) Source # 

Methods

toRow :: (a, b, c, d) -> [SQLData] Source #

(ToField a, ToField b, ToField c, ToField d, ToField e) => ToRow (a, b, c, d, e) Source # 

Methods

toRow :: (a, b, c, d, e) -> [SQLData] Source #

(ToField a, ToField b, ToField c, ToField d, ToField e, ToField f) => ToRow (a, b, c, d, e, f) Source # 

Methods

toRow :: (a, b, c, d, e, f) -> [SQLData] Source #

(ToField a, ToField b, ToField c, ToField d, ToField e, ToField f, ToField g) => ToRow (a, b, c, d, e, f, g) Source # 

Methods

toRow :: (a, b, c, d, e, f, g) -> [SQLData] Source #

(ToField a, ToField b, ToField c, ToField d, ToField e, ToField f, ToField g, ToField h) => ToRow (a, b, c, d, e, f, g, h) Source # 

Methods

toRow :: (a, b, c, d, e, f, g, h) -> [SQLData] Source #

(ToField a, ToField b, ToField c, ToField d, ToField e, ToField f, ToField g, ToField h, ToField i) => ToRow (a, b, c, d, e, f, g, h, i) Source # 

Methods

toRow :: (a, b, c, d, e, f, g, h, i) -> [SQLData] Source #

(ToField a, ToField b, ToField c, ToField d, ToField e, ToField f, ToField g, ToField h, ToField i, ToField j) => ToRow (a, b, c, d, e, f, g, h, i, j) Source # 

Methods

toRow :: (a, b, c, d, e, f, g, h, i, j) -> [SQLData] Source #

class FromRow a where Source #

A collection type that can be converted from a sequence of fields. Instances are provided for tuples up to 10 elements and lists of any length.

Note that instances can defined outside of sqlite-simple, which is often useful. For example, here's an instance for a user-defined pair:

@data User = User { name :: String, fileQuota :: Int }

instance FromRow User where fromRow = User <$> field <*> field @

The number of calls to field must match the number of fields returned in a single row of the query result. Otherwise, a ConversionFailed exception will be thrown.

Note the caveats associated with user-defined implementations of fromRow.

Minimal complete definition

fromRow

Instances

FromField a => FromRow [a] Source # 

Methods

fromRow :: RowParser [a] Source #

FromField a => FromRow (Only a) Source # 

Methods

fromRow :: RowParser (Only a) Source #

(FromField a, FromField b) => FromRow (a, b) Source # 

Methods

fromRow :: RowParser (a, b) Source #

(FromRow a, FromRow b) => FromRow ((:.) a b) Source # 

Methods

fromRow :: RowParser (a :. b) Source #

(FromField a, FromField b, FromField c) => FromRow (a, b, c) Source # 

Methods

fromRow :: RowParser (a, b, c) Source #

(FromField a, FromField b, FromField c, FromField d) => FromRow (a, b, c, d) Source # 

Methods

fromRow :: RowParser (a, b, c, d) Source #

(FromField a, FromField b, FromField c, FromField d, FromField e) => FromRow (a, b, c, d, e) Source # 

Methods

fromRow :: RowParser (a, b, c, d, e) Source #

(FromField a, FromField b, FromField c, FromField d, FromField e, FromField f) => FromRow (a, b, c, d, e, f) Source # 

Methods

fromRow :: RowParser (a, b, c, d, e, f) Source #

(FromField a, FromField b, FromField c, FromField d, FromField e, FromField f, FromField g) => FromRow (a, b, c, d, e, f, g) Source # 

Methods

fromRow :: RowParser (a, b, c, d, e, f, g) Source #

(FromField a, FromField b, FromField c, FromField d, FromField e, FromField f, FromField g, FromField h) => FromRow (a, b, c, d, e, f, g, h) Source # 

Methods

fromRow :: RowParser (a, b, c, d, e, f, g, h) Source #

(FromField a, FromField b, FromField c, FromField d, FromField e, FromField f, FromField g, FromField h, FromField i) => FromRow (a, b, c, d, e, f, g, h, i) Source # 

Methods

fromRow :: RowParser (a, b, c, d, e, f, g, h, i) Source #

(FromField a, FromField b, FromField c, FromField d, FromField e, FromField f, FromField g, FromField h, FromField i, FromField j) => FromRow (a, b, c, d, e, f, g, h, i, j) Source # 

Methods

fromRow :: RowParser (a, b, c, d, e, f, g, h, i, j) Source #

newtype Only a :: * -> * #

The 1-tuple type or single-value "collection".

This type is structurally equivalent to the Identity type, but its intent is more about serving as the anonymous 1-tuple type missing from Haskell for attaching typeclass instances.

Parameter usage example:

encodeSomething (Only (42::Int))

Result usage example:

xs <- decodeSomething
forM_ xs $ \(Only id) -> {- ... -}

Constructors

Only 

Fields

Instances

Functor Only 

Methods

fmap :: (a -> b) -> Only a -> Only b #

(<$) :: a -> Only b -> Only a #

Eq a => Eq (Only a) 

Methods

(==) :: Only a -> Only a -> Bool #

(/=) :: Only a -> Only a -> Bool #

Data a => Data (Only a) 

Methods

gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Only a -> c (Only a) #

gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Only a) #

toConstr :: Only a -> Constr #

dataTypeOf :: Only a -> DataType #

dataCast1 :: Typeable (* -> *) t => (forall d. Data d => c (t d)) -> Maybe (c (Only a)) #

dataCast2 :: Typeable (* -> * -> *) t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Only a)) #

gmapT :: (forall b. Data b => b -> b) -> Only a -> Only a #

gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Only a -> r #

gmapQr :: (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Only a -> r #

gmapQ :: (forall d. Data d => d -> u) -> Only a -> [u] #

gmapQi :: Int -> (forall d. Data d => d -> u) -> Only a -> u #

gmapM :: Monad m => (forall d. Data d => d -> m d) -> Only a -> m (Only a) #

gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Only a -> m (Only a) #

gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Only a -> m (Only a) #

Ord a => Ord (Only a) 

Methods

compare :: Only a -> Only a -> Ordering #

(<) :: Only a -> Only a -> Bool #

(<=) :: Only a -> Only a -> Bool #

(>) :: Only a -> Only a -> Bool #

(>=) :: Only a -> Only a -> Bool #

max :: Only a -> Only a -> Only a #

min :: Only a -> Only a -> Only a #

Read a => Read (Only a) 
Show a => Show (Only a) 

Methods

showsPrec :: Int -> Only a -> ShowS #

show :: Only a -> String #

showList :: [Only a] -> ShowS #

Generic (Only a) 

Associated Types

type Rep (Only a) :: * -> * #

Methods

from :: Only a -> Rep (Only a) x #

to :: Rep (Only a) x -> Only a #

NFData a => NFData (Only a) 

Methods

rnf :: Only a -> () #

ToField a => ToRow (Only a) Source # 

Methods

toRow :: Only a -> [SQLData] Source #

FromField a => FromRow (Only a) Source # 

Methods

fromRow :: RowParser (Only a) Source #

type Rep (Only a) 
type Rep (Only a) = D1 * (MetaData "Only" "Data.Tuple.Only" "Only-0.1-K3HSyq2koL8JtFXn0ZkrT6" True) (C1 * (MetaCons "Only" PrefixI True) (S1 * (MetaSel (Just Symbol "fromOnly") NoSourceUnpackedness NoSourceStrictness DecidedLazy) (Rec0 * a)))

data h :. t infixr 3 Source #

A composite type to parse your custom data structures without having to define dummy newtype wrappers every time.

instance FromRow MyData where ...
instance FromRow MyData2 where ...

then I can do the following for free:

res <- query' c "..."
forM res $ \(MyData{..} :. MyData2{..}) -> do
  ....

Constructors

h :. t infixr 3 

Instances

(Eq t, Eq h) => Eq ((:.) h t) Source # 

Methods

(==) :: (h :. t) -> (h :. t) -> Bool #

(/=) :: (h :. t) -> (h :. t) -> Bool #

(Ord t, Ord h) => Ord ((:.) h t) Source # 

Methods

compare :: (h :. t) -> (h :. t) -> Ordering #

(<) :: (h :. t) -> (h :. t) -> Bool #

(<=) :: (h :. t) -> (h :. t) -> Bool #

(>) :: (h :. t) -> (h :. t) -> Bool #

(>=) :: (h :. t) -> (h :. t) -> Bool #

max :: (h :. t) -> (h :. t) -> h :. t #

min :: (h :. t) -> (h :. t) -> h :. t #

(Read t, Read h) => Read ((:.) h t) Source # 

Methods

readsPrec :: Int -> ReadS (h :. t) #

readList :: ReadS [h :. t] #

readPrec :: ReadPrec (h :. t) #

readListPrec :: ReadPrec [h :. t] #

(Show t, Show h) => Show ((:.) h t) Source # 

Methods

showsPrec :: Int -> (h :. t) -> ShowS #

show :: (h :. t) -> String #

showList :: [h :. t] -> ShowS #

(ToRow a, ToRow b) => ToRow ((:.) a b) Source # 

Methods

toRow :: (a :. b) -> [SQLData] Source #

(FromRow a, FromRow b) => FromRow ((:.) a b) Source # 

Methods

fromRow :: RowParser (a :. b) Source #

newtype Statement Source #

An SQLite prepared statement.

Constructors

Statement 

newtype ColumnIndex Source #

Index of a column in a result set. Column indices start from 0.

Constructors

ColumnIndex ColumnIndex 

Instances

Enum ColumnIndex Source # 
Eq ColumnIndex Source # 
Integral ColumnIndex Source # 
Num ColumnIndex Source # 
Ord ColumnIndex Source # 
Real ColumnIndex Source # 

data NamedParam where Source #

Constructors

(:=) :: ToField v => Text -> v -> NamedParam infixr 3 

Connections

open :: String -> IO Connection Source #

Open a database connection to a given file. Will throw an exception if it cannot connect.

Every open must be closed with a call to close.

If you specify ":memory:" or an empty string as the input filename, then a private, temporary in-memory database is created for the connection. This database will vanish when you close the connection.

close :: Connection -> IO () Source #

Close a database connection.

withConnection :: String -> (Connection -> IO a) -> IO a Source #

Opens a database connection, executes an action using this connection, and closes the connection, even in the presence of exceptions.

setTrace :: Connection -> Maybe (Text -> IO ()) -> IO () Source #

http://www.sqlite.org/c3ref/profile.html

Enable/disable tracing of SQL execution. Tracing can be disabled by setting Nothing as the logger callback.

Warning: If the logger callback throws an exception, your whole program may crash. Enable only for debugging!

Queries that return results

query :: (ToRow q, FromRow r) => Connection -> Query -> q -> IO [r] Source #

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:

query_ :: FromRow r => Connection -> Query -> IO [r] Source #

A version of query that does not perform query substitution.

queryWith :: ToRow q => RowParser r -> Connection -> Query -> q -> IO [r] Source #

A version of query that takes an explicit RowParser.

queryWith_ :: RowParser r -> Connection -> Query -> IO [r] Source #

A version of query that does not perform query substitution and takes an explicit RowParser.

queryNamed :: FromRow r => Connection -> Query -> [NamedParam] -> IO [r] Source #

A version of query where the query parameters (placeholders) are named.

Example:

r <- queryNamed c "SELECT * FROM posts WHERE id=:id AND date>=:date" [":id" := postId, ":date" := afterDate]

lastInsertRowId :: Connection -> IO Int64 Source #

Returns the rowid of the most recent successful INSERT on the given database connection.

See also http://www.sqlite.org/c3ref/last_insert_rowid.html.

changes :: Connection -> IO Int Source #

http://www.sqlite.org/c3ref/changes.html

Return the number of rows that were changed, inserted, or deleted by the most recent INSERT, DELETE, or UPDATE statement.

totalChanges :: Connection -> IO Int Source #

http://www.sqlite.org/c3ref/total_changes.html

Return the total number of row changes caused by INSERT, DELETE, or UPDATE statements since the Database was opened.

Queries that stream results

fold :: (FromRow row, ToRow params) => Connection -> Query -> params -> a -> (a -> row -> IO a) -> IO a Source #

Perform a SELECT or other SQL query that is expected to return results. Results are converted and fed into the action callback as they are being retrieved from the database.

This allows gives the possibility of processing results in constant space (for instance writing them to disk).

Exceptions that may be thrown:

fold_ :: FromRow row => Connection -> Query -> a -> (a -> row -> IO a) -> IO a Source #

A version of fold which does not perform parameter substitution.

foldNamed :: FromRow row => Connection -> Query -> [NamedParam] -> a -> (a -> row -> IO a) -> IO a Source #

A version of fold where the query parameters (placeholders) are named.

Statements that do not return results

execute :: ToRow q => Connection -> Query -> q -> IO () Source #

Execute an INSERT, UPDATE, or other SQL query that is not expected to return results.

Throws FormatError if the query could not be formatted correctly.

execute_ :: Connection -> Query -> IO () Source #

A version of execute that does not perform query substitution.

executeMany :: ToRow q => Connection -> Query -> [q] -> IO () Source #

Execute a multi-row INSERT, UPDATE, or other SQL query that is not expected to return results.

Throws FormatError if the query could not be formatted correctly.

executeNamed :: Connection -> Query -> [NamedParam] -> IO () Source #

A version of execute where the query parameters (placeholders) are named.

Transactions

withTransaction :: Connection -> IO a -> IO a Source #

Run an IO action inside a SQL transaction started with BEGIN TRANSACTION. If the action throws any kind of an exception, the transaction will be rolled back with ROLLBACK TRANSACTION. Otherwise the results are committed with COMMIT TRANSACTION.

withImmediateTransaction :: Connection -> IO a -> IO a Source #

Run an IO action inside a SQL transaction started with BEGIN IMMEDIATE TRANSACTION, which immediately blocks all other database connections from writing. The default SQLite3 BEGIN TRANSACTION does not acquire the write lock on BEGIN nor on SELECT but waits until you try to change data. If the action throws any kind of an exception, the transaction will be rolled back with ROLLBACK TRANSACTION. Otherwise the results are committed with COMMIT TRANSACTION.

withExclusiveTransaction :: Connection -> IO a -> IO a Source #

Run an IO action inside a SQL transaction started with BEGIN EXCLUSIVE TRANSACTION, which immediately blocks all other database connections from writing, and other connections from reading (exception: read_uncommitted connections are allowed to read.) If the action throws any kind of an exception, the transaction will be rolled back with ROLLBACK TRANSACTION. Otherwise the results are committed with COMMIT TRANSACTION.

Low-level statement API for stream access and prepared statements

openStatement :: Connection -> Query -> IO Statement Source #

Opens a prepared statement. A prepared statement must always be closed with a corresponding call to closeStatement before closing the connection. Use nextRow to iterate on the values returned. Once nextRow returns Nothing, you need to invoke reset before reexecuting the statement again with nextRow.

closeStatement :: Statement -> IO () Source #

Closes a prepared statement.

withStatement :: Connection -> Query -> (Statement -> IO a) -> IO a Source #

Opens a prepared statement, executes an action using this statement, and closes the statement, even in the presence of exceptions.

bind :: ToRow params => Statement -> params -> IO () Source #

Binds parameters to a prepared statement. Once nextRow returns Nothing, the statement must be reset with the reset function before it can be executed again by calling nextRow.

bindNamed :: Statement -> [NamedParam] -> IO () Source #

Binds named parameters to a prepared statement.

reset :: Statement -> IO () Source #

Resets a statement. This does not reset bound parameters, if any, but allows the statement to be reexecuted again by invoking nextRow.

columnName :: Statement -> ColumnIndex -> IO Text Source #

Return the name of a a particular column in the result set of a Statement. Throws an ArrayException if the colum index is out of bounds.

http://www.sqlite.org/c3ref/column_name.html

columnCount :: Statement -> IO ColumnIndex Source #

Return number of columns in the query

withBind :: ToRow params => Statement -> params -> IO a -> IO a Source #

Binds parameters to a prepared statement, and resets the statement when the callback completes, even in the presence of exceptions.

Use withBind to reuse prepared statements. Because it resets the statement after each usage, it avoids a pitfall involving implicit transactions. SQLite creates an implicit transaction if you don't say BEGIN explicitly, and does not commit it until all active statements are finished with either reset or closeStatement.

nextRow :: FromRow r => Statement -> IO (Maybe r) Source #

Extracts the next row from the prepared statement.

Exceptions

data FormatError Source #

Exception thrown if a Query was malformed. This may occur if the number of '?' characters in the query string does not match the number of parameters provided.

Constructors

FormatError 

data ResultError Source #

Exception thrown if conversion from a SQL value to a Haskell value fails.

Constructors

Incompatible

The SQL and Haskell types are not compatible.

UnexpectedNull

A SQL NULL was encountered when the Haskell type did not permit it.

ConversionFailed

The SQL value could not be parsed, or could not be represented as a valid Haskell value, or an unexpected low-level error occurred (e.g. mismatch between metadata and actual data in a row).

data SQLError :: * #

Exception thrown when SQLite3 reports an error.

direct-sqlite may throw other types of exceptions if you misuse the API.

Constructors

SQLError 

Fields

data Error :: * #

Constructors

ErrorOK

Successful result

ErrorError

SQL error or missing database

ErrorInternal

Internal logic error in SQLite

ErrorPermission

Access permission denied

ErrorAbort

Callback routine requested an abort

ErrorBusy

The database file is locked

ErrorLocked

A table in the database is locked

ErrorNoMemory

A malloc() failed

ErrorReadOnly

Attempt to write a readonly database

ErrorInterrupt

Operation terminated by sqlite3_interrupt()

ErrorIO

Some kind of disk I/O error occurred

ErrorCorrupt

The database disk image is malformed

ErrorNotFound

Unknown opcode in sqlite3_file_control()

ErrorFull

Insertion failed because database is full

ErrorCan'tOpen

Unable to open the database file

ErrorProtocol

Database lock protocol error

ErrorEmpty

Database is empty

ErrorSchema

The database schema changed

ErrorTooBig

String or BLOB exceeds size limit

ErrorConstraint

Abort due to constraint violation

ErrorMismatch

Data type mismatch

ErrorMisuse

Library used incorrectly

ErrorNoLargeFileSupport

Uses OS features not supported on host

ErrorAuthorization

Authorization denied

ErrorFormat

Auxiliary database format error

ErrorRange

2nd parameter to sqlite3_bind out of range

ErrorNotADatabase

File opened that is not a database file

ErrorRow

sqlite3_step() has another row ready

ErrorDone

sqlite3_step() has finished executing

Instances

Eq Error 

Methods

(==) :: Error -> Error -> Bool #

(/=) :: Error -> Error -> Bool #

Show Error 

Methods

showsPrec :: Int -> Error -> ShowS #

show :: Error -> String #

showList :: [Error] -> ShowS #

FFIType Error CError 

Methods

toFFI :: Error -> CError #

fromFFI :: CError -> Error #