esqueleto-2.4.3: Type-safe EDSL for SQL queries on persistent backends.

Safe HaskellNone
LanguageHaskell98

Database.Esqueleto.Internal.Language

Contents

Description

This is an internal module, anything exported by this module may change without a major version bump. Please use only Database.Esqueleto if possible.

Synopsis

The pretty face

class (Functor query, Applicative query, Monad query) => Esqueleto query expr backend | query -> expr backend, expr -> query backend where Source

Finally tagless representation of esqueleto's EDSL.

Methods

fromStart :: (PersistEntity a, PersistEntityBackend a ~ backend) => query (expr (PreprocessedFrom (expr (Entity a)))) Source

(Internal) Start a from query with an entity. from does two kinds of magic using fromStart, fromJoin and fromFinish:

  1. The simple but tedious magic of allowing tuples to be used.
  2. The more advanced magic of creating JOINs. The JOIN is processed from right to left. The rightmost entity of the JOIN is created with fromStart. Each JOIN step is then translated into a call to fromJoin. In the end, fromFinish is called to materialize the JOIN.

fromStartMaybe :: (PersistEntity a, PersistEntityBackend a ~ backend) => query (expr (PreprocessedFrom (expr (Maybe (Entity a))))) Source

(Internal) Same as fromStart, but entity may be missing.

fromJoin :: IsJoinKind join => expr (PreprocessedFrom a) -> expr (PreprocessedFrom b) -> query (expr (PreprocessedFrom (join a b))) Source

(Internal) Do a JOIN.

fromFinish :: expr (PreprocessedFrom a) -> query a Source

(Internal) Finish a JOIN.

where_ :: expr (Value Bool) -> query () Source

WHERE clause: restrict the query's result.

on :: expr (Value Bool) -> query () Source

ON clause: restrict the a JOIN's result. The ON clause will be applied to the last JOIN that does not have an ON clause yet. If there are no JOINs without ON clauses (either because you didn't do any JOIN, or because all JOINs already have their own ON clauses), a runtime exception OnClauseWithoutMatchingJoinException is thrown. ON clauses are optional when doing JOINs.

On the simple case of doing just one JOIN, for example

select $
from $ \(foo `InnerJoin` bar) -> do
  on (foo ^. FooId ==. bar ^. BarFooId)
  ...

there's no ambiguity and the rules above just mean that you're allowed to call on only once (as in SQL). If you have many joins, then the ons are applied on the reverse order that the JOINs appear. For example:

select $
from $ \(foo `InnerJoin` bar `InnerJoin` baz) -> do
  on (baz ^. BazId ==. bar ^. BarBazId)
  on (foo ^. FooId ==. bar ^. BarFooId)
  ...

The order is reversed in order to improve composability. For example, consider query1 and query2 below:

let query1 =
      from $ \(foo `InnerJoin` bar) -> do
        on (foo ^. FooId ==. bar ^. BarFooId)
    query2 =
      from $ \(mbaz `LeftOuterJoin` quux) -> do
        return (mbaz ?. BazName, quux)
    test1 =      (,) <$> query1 <*> query2
    test2 = flip (,) <$> query2 <*> query1

If the order was not reversed, then test2 would be broken: query1's on would refer to query2's LeftOuterJoin.

groupBy :: ToSomeValues expr a => a -> query () Source

GROUP BY clause. You can enclose multiple columns in a tuple.

select $ from \(foo `InnerJoin` bar) -> do
  on (foo ^. FooBarId ==. bar ^. BarId)
  groupBy (bar ^. BarId, bar ^. BarName)
  return (bar ^. BarId, bar ^. BarName, countRows)

With groupBy you can sort by aggregate functions, like so (we used let to restrict the more general countRows to SqlExpr (Value Int) to avoid ambiguity---the second use of countRows has its type restricted by the :: Int below):

r <- select $ from \(foo `InnerJoin` bar) -> do
  on (foo ^. FooBarId ==. bar ^. BarId)
  groupBy $ bar ^. BarName
  let countRows' = countRows
  orderBy [asc countRows']
  return (bar ^. BarName, countRows')
forM_ r $ \(Value name, Value count) -> do
  print name
  print (count :: Int)

orderBy :: [expr OrderBy] -> query () Source

ORDER BY clause. See also asc and desc.

Multiple calls to orderBy get concatenated on the final query, including distinctOnOrderBy.

asc :: PersistField a => expr (Value a) -> expr OrderBy Source

Ascending order of this field or expression.

desc :: PersistField a => expr (Value a) -> expr OrderBy Source

Descending order of this field or expression.

limit :: Int64 -> query () Source

LIMIT. Limit the number of returned rows.

offset :: Int64 -> query () Source

OFFSET. Usually used with limit.

distinct :: query a -> query a Source

DISTINCT. Change the current SELECT into SELECT DISTINCT. For example:

select $ distinct $
  from \foo -> do
  ...

Note that this also has the same effect:

select $
  from \foo -> do
  distinct (return ())
  ...

Since: 2.2.4

distinctOn :: [expr DistinctOn] -> query a -> query a Source

DISTINCT ON. Change the current SELECT into SELECT DISTINCT ON (expressions). For example:

select $
  from \foo ->
  distinctOn [don (foo ^. FooName), don (foo ^. FooState)] $ do
  ...

You can also chain different calls to distinctOn. The above is equivalent to:

select $
  from \foo ->
  distinctOn [don (foo ^. FooName)] $
  distinctOn [don (foo ^. FooState)] $ do
  ...

Each call to distinctOn adds more expressions. Calls to distinctOn override any calls to distinct.

Note that PostgreSQL requires the expressions on DISTINCT ON to be the first ones to appear on a ORDER BY. This is not managed automatically by esqueleto, keeping its spirit of trying to be close to raw SQL.

Supported by PostgreSQL only.

Since: 2.2.4

don :: expr (Value a) -> expr DistinctOn Source

Erase an expression's type so that it's suitable to be used by distinctOn.

Since: 2.2.4

distinctOnOrderBy :: [expr OrderBy] -> query a -> query a Source

A convenience function that calls both distinctOn and orderBy. In other words,

distinctOnOrderBy [asc foo, desc bar, desc quux] $ do
  ...

is the same as:

distinctOn [don foo, don  bar, don  quux] $ do
  orderBy  [asc foo, desc bar, desc quux]
  ...

Since: 2.2.4

rand :: expr OrderBy Source

ORDER BY random() clause.

Since: 1.3.10

having :: expr (Value Bool) -> query () Source

HAVING.

Since: 1.2.2

locking :: LockingKind -> query () Source

Add a locking clause to the query. Please read LockingKind documentation and your RDBMS manual.

If multiple calls to locking are made on the same query, the last one is used.

Since: 2.2.7

sub_select :: PersistField a => query (expr (Value a)) -> expr (Value a) Source

Execute a subquery SELECT in an expression. Returns a simple value so should be used only when the SELECT query is guaranteed to return just one row.

sub_selectDistinct :: PersistField a => query (expr (Value a)) -> expr (Value a) Source

Deprecated: Since 2.2.4: use sub_select and distinct.

Same as sub_select but using SELECT DISTINCT.

(^.) :: (PersistEntity val, PersistField typ) => expr (Entity val) -> EntityField val typ -> expr (Value typ) infixl 9 Source

Project a field of an entity.

(?.) :: (PersistEntity val, PersistField typ) => expr (Maybe (Entity val)) -> EntityField val typ -> expr (Value (Maybe typ)) Source

Project a field of an entity that may be null.

val :: PersistField typ => typ -> expr (Value typ) Source

Lift a constant value from Haskell-land to the query.

isNothing :: PersistField typ => expr (Value (Maybe typ)) -> expr (Value Bool) Source

IS NULL comparison.

just :: expr (Value typ) -> expr (Value (Maybe typ)) Source

Analogous to Just, promotes a value of type typ into one of type Maybe typ. It should hold that val . Just === just . val.

nothing :: expr (Value (Maybe typ)) Source

NULL value.

joinV :: expr (Value (Maybe (Maybe typ))) -> expr (Value (Maybe typ)) Source

Join nested Maybes in a Value into one. This is useful when calling aggregate functions on nullable fields.

countRows :: Num a => expr (Value a) Source

COUNT(*) value.

count :: Num a => expr (Value typ) -> expr (Value a) Source

COUNT.

countDistinct :: Num a => expr (Value typ) -> expr (Value a) Source

COUNT(DISTINCT x).

Since: 2.4.1

not_ :: expr (Value Bool) -> expr (Value Bool) Source

(==.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 Source

(>=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 Source

(>.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 Source

(<=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 Source

(<.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 Source

(!=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool) infix 4 Source

(&&.) :: expr (Value Bool) -> expr (Value Bool) -> expr (Value Bool) infixr 3 Source

(||.) :: expr (Value Bool) -> expr (Value Bool) -> expr (Value Bool) infixr 2 Source

(+.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a) infixl 6 Source

(-.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a) infixl 6 Source

(/.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a) infixl 7 Source

(*.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a) infixl 7 Source

random_ :: (PersistField a, Num a) => expr (Value a) Source

round_ :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b) Source

ceiling_ :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b) Source

floor_ :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b) Source

sum_ :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value (Maybe b)) Source

min_ :: PersistField a => expr (Value a) -> expr (Value (Maybe a)) Source

max_ :: PersistField a => expr (Value a) -> expr (Value (Maybe a)) Source

avg_ :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value (Maybe b)) Source

castNum :: (Num a, Num b) => expr (Value a) -> expr (Value b) Source

Allow a number of one type to be used as one of another type via an implicit cast. An explicit cast is not made, this function changes only the types on the Haskell side.

Caveat: Trying to use castNum from Double to Int will not result in an integer, the original fractional number will still be used! Use round_, ceiling_ or floor_ instead.

Safety: This operation is mostly safe due to the Num constraint between the types and the fact that RDBMSs usually allow numbers of different types to be used interchangeably. However, there may still be issues with the query not being accepted by the RDBMS or persistent not being able to parse it.

Since: 2.2.9

castNumM :: (Num a, Num b) => expr (Value (Maybe a)) -> expr (Value (Maybe b)) Source

Same as castNum, but for nullable values.

Since: 2.2.9

coalesce :: PersistField a => [expr (Value (Maybe a))] -> expr (Value (Maybe a)) Source

COALESCE function. Evaluates the arguments in order and returns the value of the first non-NULL expression, or NULL (Nothing) otherwise. Some RDBMSs (such as SQLite) require at least two arguments; please refer to the appropriate documentation.

Since: 1.4.3

coalesceDefault :: PersistField a => [expr (Value (Maybe a))] -> expr (Value a) -> expr (Value a) Source

Like coalesce, but takes a non-nullable expression placed at the end of the expression list, which guarantees a non-NULL result.

Since: 1.4.3

lower_ :: SqlString s => expr (Value s) -> expr (Value s) Source

LOWER function.

like :: SqlString s => expr (Value s) -> expr (Value s) -> expr (Value Bool) infixr 2 Source

LIKE operator.

ilike :: SqlString s => expr (Value s) -> expr (Value s) -> expr (Value Bool) infixr 2 Source

ILIKE operator (case-insensitive LIKE).

Supported by PostgreSQL only.

Since: 2.2.3

(%) :: SqlString s => expr (Value s) Source

The string %. May be useful while using like and concatenation (concat_ or ++., depending on your database). Note that you always have to type the parenthesis, for example:

name `like` (%) ++. val "John" ++. (%)

concat_ :: SqlString s => [expr (Value s)] -> expr (Value s) Source

The CONCAT function with a variable number of parameters. Supported by MySQL and PostgreSQL.

(++.) :: SqlString s => expr (Value s) -> expr (Value s) -> expr (Value s) infixr 5 Source

The || string concatenation operator (named after Haskell's ++ in order to avoid naming clash with ||.). Supported by SQLite and PostgreSQL.

castString :: (SqlString s, SqlString r) => expr (Value s) -> expr (Value r) Source

Cast a string type into Text. This function is very useful if you want to use newtypes, or if you want to apply functions such as like to strings of different types.

Safety: This is a slightly unsafe function, especially if you have defined your own instances of SqlString. Also, since Maybe is an instance of SqlString, it's possible to turn a nullable value into a non-nullable one. Avoid using this function if possible.

subList_select :: PersistField a => query (expr (Value a)) -> expr (ValueList a) Source

Execute a subquery SELECT in an expression. Returns a list of values.

subList_selectDistinct :: PersistField a => query (expr (Value a)) -> expr (ValueList a) Source

Deprecated: Since 2.2.4: use subList_select and distinct.

Same as sublist_select but using SELECT DISTINCT.

valList :: PersistField typ => [typ] -> expr (ValueList typ) Source

Lift a list of constant value from Haskell-land to the query.

justList :: expr (ValueList typ) -> expr (ValueList (Maybe typ)) Source

Same as just but for ValueList. Most of the time you won't need it, though, because you can use just from inside subList_select or Just from inside valList.

Since: 2.2.12

in_ :: PersistField typ => expr (Value typ) -> expr (ValueList typ) -> expr (Value Bool) Source

IN operator. For example if you want to select all Persons by a list of IDs:

SELECT *
FROM Person
WHERE Person.id IN (?)

In esqueleto, we may write the same query above as:

select $
from $ \person -> do
where_ $ person ^. PersonId in_ valList personIds
return person

Where personIds is of type [Key Person].

notIn :: PersistField typ => expr (Value typ) -> expr (ValueList typ) -> expr (Value Bool) Source

NOT IN operator.

exists :: query () -> expr (Value Bool) Source

EXISTS operator. For example:

select $
from $ \person -> do
where_ $ exists $
         from $ \post -> do
         where_ (post ^. BlogPostAuthorId ==. person ^. PersonId)
return person

notExists :: query () -> expr (Value Bool) Source

NOT EXISTS operator.

set :: PersistEntity val => expr (Entity val) -> [expr (Update val)] -> query () Source

SET clause used on UPDATEs. Note that while it's not a type error to use this function on a SELECT, it will most certainly result in a runtime error.

(=.) :: (PersistEntity val, PersistField typ) => EntityField val typ -> expr (Value typ) -> expr (Update val) infixr 3 Source

(+=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val) infixr 3 Source

(-=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val) infixr 3 Source

(*=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val) infixr 3 Source

(/=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val) infixr 3 Source

(<#) :: (a -> b) -> expr (Value a) -> expr (Insertion b) Source

Apply a PersistField constructor to expr Value arguments.

(<&>) :: expr (Insertion (a -> b)) -> expr (Value a) -> expr (Insertion b) Source

Apply extra expr Value arguments to a PersistField constructor

case_ :: PersistField a => [(expr (Value Bool), expr (Value a))] -> expr (Value a) -> expr (Value a) Source

CASE statement. For example:

select $
return $
case_
   [ when_
       (exists $
       from $ \p -> do
       where_ (p ^. PersonName ==. val "Mike"))
     then_
       (sub_select $
       from $ \v -> do
       let sub =
               from $ \c -> do
               where_ (c ^. PersonName ==. val "Mike")
               return (c ^. PersonFavNum)
       where_ (v ^. PersonFavNum >. sub_select sub)
       return $ count (v ^. PersonName) +. val (1 :: Int)) ]
   (else_ $ val (-1))

This query is a bit complicated, but basically it checks if a person named "Mike" exists, and if that person does, run the subquery to find out how many people have a ranking (by Fav Num) higher than "Mike".

NOTE: There are a few things to be aware about this statement.

  • This only implements the full CASE statement, it does not implement the "simple" CASE statement.
  • At least one when_ and then_ is mandatory otherwise it will emit an error.
  • The else_ is also mandatory, unlike the SQL statement in which if the ELSE is omitted it will return a NULL. You can reproduce this via nothing.

Since: 2.1.2

toBaseId :: ToBaseId ent => expr (Value (Key ent)) -> expr (Value (Key (BaseEnt ent))) Source

Convert an entity's key into another entity's.

This function is to be used when you change an entity's Id to be that of another entity. For example:

Bar
  barNum Int
Foo
  Id BarId
  fooNum Int

For this example, declare:

instance ToBaseId Foo where
  type BaseEnt Foo = Bar
  toBaseIdWitness = FooKey

Now you're able to write queries such as:

select $
from $ (bar `InnerJoin` foo) -> do
on (toBaseId (foo ^. FooId) ==. bar ^. BarId)
return (bar, foo)

Note: this function may be unsafe to use in conditions not like the one of the example above.

Since: 2.4.3

from :: From query expr backend a => (a -> query b) -> query b Source

FROM clause: bring entities into scope.

This function internally uses two type classes in order to provide some flexibility of how you may call it. Internally we refer to these type classes as the two different magics.

The innermost magic allows you to use from with the following types:

  • expr (Entity val), which brings a single entity into scope.
  • expr (Maybe (Entity val)), which brings a single entity that may be NULL into scope. Used for OUTER JOINs.
  • A JOIN of any other two types allowed by the innermost magic, where a JOIN may be an InnerJoin, a CrossJoin, a LeftOuterJoin, a RightOuterJoin, or a FullOuterJoin. The JOINs have left fixity.

The outermost magic allows you to use from on any tuples of types supported by innermost magic (and also tuples of tuples, and so on), up to 8-tuples.

Note that using from for the same entity twice does work and corresponds to a self-join. You don't even need to use two different calls to from, you may use a JOIN or a tuple.

The following are valid examples of uses of from (the types of the arguments of the lambda are inside square brackets):

from $ \person -> ...
from $ \(person, blogPost) -> ...
from $ \(p `LeftOuterJoin` mb) -> ...
from $ \(p1 `InnerJoin` f `InnerJoin` p2) -> ...
from $ \((p1 `InnerJoin` f) `InnerJoin` p2) -> ...

The types of the arguments to the lambdas above are, respectively:

person
  :: ( Esqueleto query expr backend
     , PersistEntity Person
     , PersistEntityBackend Person ~ backend
     ) => expr (Entity Person)
(person, blogPost)
  :: (...) => (expr (Entity Person), expr (Entity BlogPost))
(p `LeftOuterJoin` mb)
  :: (...) => InnerJoin (expr (Entity Person)) (expr (Maybe (Entity BlogPost)))
(p1 `InnerJoin` f `InnerJoin` p2)
  :: (...) => InnerJoin
                (InnerJoin (expr (Entity Person))
                           (expr (Entity Follow)))
                (expr (Entity Person))
(p1 `InnerJoin` (f `InnerJoin` p2)) ::
  :: (...) => InnerJoin
                (expr (Entity Person))
                (InnerJoin (expr (Entity Follow))
                           (expr (Entity Person)))

Note that some backends may not support all kinds of JOINs.

data Value a Source

A single value (as opposed to a whole entity). You may use (^.) or (?.) to get a Value from an Entity.

Constructors

Value a 

Instances

Functor Value Source

Since: 1.4.4

ToSomeValues SqlExpr (SqlExpr (Value a)) Source 
Eq a => Eq (Value a) Source 
Ord a => Ord (Value a) Source 
Show a => Show (Value a) Source 
PersistField a => SqlSelect (SqlExpr (Value a)) (Value a) Source

You may return any single value (i.e. a single column) from a select query.

unValue :: Value a -> a Source

Unwrap a Value.

Since: 1.4.1

data ValueList a Source

A list of single values. There's a limited set of functions able to work with this data type (such as subList_select, valList, in_ and exists).

Constructors

ValueList a 

Instances

Eq a => Eq (ValueList a) Source 
Ord a => Ord (ValueList a) Source 
Show a => Show (ValueList a) Source 

data SomeValue expr where Source

A wrapper type for for any expr (Value a) for all a.

Constructors

SomeValue :: Esqueleto query expr backend => expr (Value a) -> SomeValue expr 

class ToSomeValues expr a where Source

A class of things that can be converted into a list of SomeValue. It has instances for tuples and is the reason why groupBy can take tuples, like groupBy (foo ^. FooId, foo ^. FooName, foo ^. FooType).

Methods

toSomeValues :: a -> [SomeValue expr] Source

Instances

ToSomeValues SqlExpr (SqlExpr (Value a)) Source 
(ToSomeValues expr a, ToSomeValues expr b) => ToSomeValues expr (a, b) Source 
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c) => ToSomeValues expr (a, b, c) Source 
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d) => ToSomeValues expr (a, b, c, d) Source 
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d, ToSomeValues expr e) => ToSomeValues expr (a, b, c, d, e) Source 
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d, ToSomeValues expr e, ToSomeValues expr f) => ToSomeValues expr (a, b, c, d, e, f) Source 
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d, ToSomeValues expr e, ToSomeValues expr f, ToSomeValues expr g) => ToSomeValues expr (a, b, c, d, e, f, g) Source 
(ToSomeValues expr a, ToSomeValues expr b, ToSomeValues expr c, ToSomeValues expr d, ToSomeValues expr e, ToSomeValues expr f, ToSomeValues expr g, ToSomeValues expr h) => ToSomeValues expr (a, b, c, d, e, f, g, h) Source 

data InnerJoin a b infixl 2 Source

Data type that represents an INNER JOIN (see LeftOuterJoin for an example).

Constructors

a `InnerJoin` b infixl 2 

Instances

IsJoinKind InnerJoin Source 
(Esqueleto query expr backend, FromPreprocess query expr backend (InnerJoin a b)) => From query expr backend (InnerJoin a b) Source 

data CrossJoin a b infixl 2 Source

Data type that represents a CROSS JOIN (see LeftOuterJoin for an example).

Constructors

a `CrossJoin` b infixl 2 

Instances

IsJoinKind CrossJoin Source 
(Esqueleto query expr backend, FromPreprocess query expr backend (CrossJoin a b)) => From query expr backend (CrossJoin a b) Source 

data LeftOuterJoin a b infixl 2 Source

Data type that represents a LEFT OUTER JOIN. For example,

select $
from $ \(person `LeftOuterJoin` pet) ->
  ...

is translated into

SELECT ...
FROM Person LEFT OUTER JOIN Pet
...

See also: from.

Constructors

a `LeftOuterJoin` b infixl 2 

Instances

IsJoinKind LeftOuterJoin Source 
(Esqueleto query expr backend, FromPreprocess query expr backend (LeftOuterJoin a b)) => From query expr backend (LeftOuterJoin a b) Source 

data RightOuterJoin a b infixl 2 Source

Data type that represents a RIGHT OUTER JOIN (see LeftOuterJoin for an example).

Constructors

a `RightOuterJoin` b infixl 2 

Instances

IsJoinKind RightOuterJoin Source 
(Esqueleto query expr backend, FromPreprocess query expr backend (RightOuterJoin a b)) => From query expr backend (RightOuterJoin a b) Source 

data FullOuterJoin a b infixl 2 Source

Data type that represents a FULL OUTER JOIN (see LeftOuterJoin for an example).

Constructors

a `FullOuterJoin` b infixl 2 

Instances

IsJoinKind FullOuterJoin Source 
(Esqueleto query expr backend, FromPreprocess query expr backend (FullOuterJoin a b)) => From query expr backend (FullOuterJoin a b) Source 

data OrderBy Source

Phantom type used by orderBy, asc and desc.

data DistinctOn Source

Phantom type used by distinctOn and don.

data Update typ Source

Phantom type for a SET operation on an entity of the given type (see set and '(=.)').

data Insertion a Source

Phantom type used by insertSelect.

data LockingKind Source

Different kinds of locking clauses supported by locking.

Note that each RDBMS has different locking support. The constructors of this datatype specify only the syntax of the locking mechanism, not its semantics. For example, even though both MySQL and PostgreSQL support ForUpdate, there are no guarantees that they will behave the same.

Since: 2.2.7

Constructors

ForUpdate

FOR UPDATE syntax. Supported by MySQL, Oracle and PostgreSQL.

Since: 2.2.7

ForShare

FOR SHARE syntax. Supported by PostgreSQL.

Since: 2.2.7

LockInShareMode

LOCK IN SHARE MODE syntax. Supported by MySQL.

Since: 2.2.7

class PersistField a => SqlString a Source

Phantom class of data types that are treated as strings by the RDBMS. It has no methods because it's only used to avoid type errors such as trying to concatenate integers.

If you have a custom data type or newtype, feel free to make it an instance of this class.

Since: 2.4.0

Instances

SqlString ByteString Source

Since: 2.3.0

SqlString Text Source

Since: 2.3.0

SqlString Text Source

Since: 2.3.0

SqlString Html Source

Since: 2.3.0

(~) * a Char => SqlString [a] Source

Since: 2.3.0

SqlString a => SqlString (Maybe a) Source

Since: 2.4.0

class ToBaseId ent where Source

Class that enables one to use toBaseId to convert an entity's key on a query into another (cf. toBaseId).

Associated Types

type BaseEnt ent :: * Source

Methods

toBaseIdWitness :: Key (BaseEnt ent) -> Key ent Source

The guts

data JoinKind Source

(Internal) A kind of JOIN.

Constructors

InnerJoinKind
INNER JOIN
CrossJoinKind
CROSS JOIN
LeftOuterJoinKind
LEFT OUTER JOIN
RightOuterJoinKind
RIGHT OUTER JOIN
FullOuterJoinKind
FULL OUTER JOIN

Instances

class IsJoinKind join where Source

(Internal) Functions that operate on types (that should be) of kind JoinKind.

Methods

smartJoin :: a -> b -> join a b Source

(Internal) smartJoin a b is a JOIN of the correct kind.

reifyJoinKind :: join a b -> JoinKind Source

(Internal) Reify a JoinKind from a JOIN. This function is non-strict.

data PreprocessedFrom a Source

(Internal) Phantom type used to process from (see fromStart).

class Esqueleto query expr backend => From query expr backend a Source

(Internal) Class that implements the tuple from magic (see fromStart).

Minimal complete definition

from_

Instances

(Esqueleto query expr backend, FromPreprocess query expr backend (expr (Maybe (Entity val)))) => From query expr backend (expr (Maybe (Entity val))) Source 
(Esqueleto query expr backend, FromPreprocess query expr backend (expr (Entity val))) => From query expr backend (expr (Entity val)) Source 
(From query expr backend a, From query expr backend b) => From query expr backend (a, b) Source 
(Esqueleto query expr backend, FromPreprocess query expr backend (FullOuterJoin a b)) => From query expr backend (FullOuterJoin a b) Source 
(Esqueleto query expr backend, FromPreprocess query expr backend (RightOuterJoin a b)) => From query expr backend (RightOuterJoin a b) Source 
(Esqueleto query expr backend, FromPreprocess query expr backend (LeftOuterJoin a b)) => From query expr backend (LeftOuterJoin a b) Source 
(Esqueleto query expr backend, FromPreprocess query expr backend (CrossJoin a b)) => From query expr backend (CrossJoin a b) Source 
(Esqueleto query expr backend, FromPreprocess query expr backend (InnerJoin a b)) => From query expr backend (InnerJoin a b) Source 
(From query expr backend a, From query expr backend b, From query expr backend c) => From query expr backend (a, b, c) Source 
(From query expr backend a, From query expr backend b, From query expr backend c, From query expr backend d) => From query expr backend (a, b, c, d) Source 
(From query expr backend a, From query expr backend b, From query expr backend c, From query expr backend d, From query expr backend e) => From query expr backend (a, b, c, d, e) Source 
(From query expr backend a, From query expr backend b, From query expr backend c, From query expr backend d, From query expr backend e, From query expr backend f) => From query expr backend (a, b, c, d, e, f) Source 
(From query expr backend a, From query expr backend b, From query expr backend c, From query expr backend d, From query expr backend e, From query expr backend f, From query expr backend g) => From query expr backend (a, b, c, d, e, f, g) Source 
(From query expr backend a, From query expr backend b, From query expr backend c, From query expr backend d, From query expr backend e, From query expr backend f, From query expr backend g, From query expr backend h) => From query expr backend (a, b, c, d, e, f, g, h) Source 

class Esqueleto query expr backend => FromPreprocess query expr backend a Source

(Internal) Class that implements the JOIN from magic (see fromStart).

Minimal complete definition

fromPreprocess

Instances

(Esqueleto query expr backend, PersistEntity val, (~) * (PersistEntityBackend val) backend) => FromPreprocess query expr backend (expr (Maybe (Entity val))) Source 
(Esqueleto query expr backend, PersistEntity val, (~) * (PersistEntityBackend val) backend) => FromPreprocess query expr backend (expr (Entity val)) Source 
(Esqueleto query expr backend, FromPreprocess query expr backend a, FromPreprocess query expr backend b, IsJoinKind join) => FromPreprocess query expr backend (join a b) Source 

when_ :: expr (Value Bool) -> () -> expr a -> (expr (Value Bool), expr a) Source

Syntax sugar for case_.

Since: 2.1.2

then_ :: () Source

Syntax sugar for case_.

Since: 2.1.2

else_ :: expr a -> expr a Source

Syntax sugar for case_.

Since: 2.1.2