Safe Haskell | None |
---|---|
Language | Haskell98 |
This is an internal module, anything exported by this module may change without a major version bump. Please use only Database.Esqueleto if possible.
- class (Functor query, Applicative query, Monad query) => Esqueleto query expr backend | query -> expr backend, expr -> query backend where
- fromStart :: (PersistEntity a, PersistEntityBackend a ~ backend) => query (expr (PreprocessedFrom (expr (Entity a))))
- fromStartMaybe :: (PersistEntity a, PersistEntityBackend a ~ backend) => query (expr (PreprocessedFrom (expr (Maybe (Entity a)))))
- fromJoin :: IsJoinKind join => expr (PreprocessedFrom a) -> expr (PreprocessedFrom b) -> query (expr (PreprocessedFrom (join a b)))
- fromFinish :: expr (PreprocessedFrom a) -> query a
- where_ :: expr (Value Bool) -> query ()
- on :: expr (Value Bool) -> query ()
- groupBy :: ToSomeValues expr a => a -> query ()
- orderBy :: [expr OrderBy] -> query ()
- asc :: PersistField a => expr (Value a) -> expr OrderBy
- desc :: PersistField a => expr (Value a) -> expr OrderBy
- limit :: Int64 -> query ()
- offset :: Int64 -> query ()
- distinct :: query a -> query a
- distinctOn :: [expr DistinctOn] -> query a -> query a
- don :: expr (Value a) -> expr DistinctOn
- distinctOnOrderBy :: [expr OrderBy] -> query a -> query a
- rand :: expr OrderBy
- having :: expr (Value Bool) -> query ()
- locking :: LockingKind -> query ()
- sub_select :: PersistField a => query (expr (Value a)) -> expr (Value a)
- sub_selectDistinct :: PersistField a => query (expr (Value a)) -> expr (Value a)
- (^.) :: (PersistEntity val, PersistField typ) => expr (Entity val) -> EntityField val typ -> expr (Value typ)
- (?.) :: (PersistEntity val, PersistField typ) => expr (Maybe (Entity val)) -> EntityField val typ -> expr (Value (Maybe typ))
- val :: PersistField typ => typ -> expr (Value typ)
- isNothing :: PersistField typ => expr (Value (Maybe typ)) -> expr (Value Bool)
- just :: expr (Value typ) -> expr (Value (Maybe typ))
- nothing :: expr (Value (Maybe typ))
- joinV :: expr (Value (Maybe (Maybe typ))) -> expr (Value (Maybe typ))
- countRows :: Num a => expr (Value a)
- count :: Num a => expr (Value typ) -> expr (Value a)
- countDistinct :: Num a => expr (Value typ) -> expr (Value a)
- not_ :: expr (Value Bool) -> expr (Value Bool)
- (==.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
- (>=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
- (>.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
- (<=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
- (<.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
- (!=.) :: PersistField typ => expr (Value typ) -> expr (Value typ) -> expr (Value Bool)
- (&&.) :: expr (Value Bool) -> expr (Value Bool) -> expr (Value Bool)
- (||.) :: expr (Value Bool) -> expr (Value Bool) -> expr (Value Bool)
- (+.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)
- (-.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)
- (/.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)
- (*.) :: PersistField a => expr (Value a) -> expr (Value a) -> expr (Value a)
- random_ :: (PersistField a, Num a) => expr (Value a)
- round_ :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b)
- ceiling_ :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b)
- floor_ :: (PersistField a, Num a, PersistField b, Num b) => expr (Value a) -> expr (Value b)
- sum_ :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value (Maybe b))
- min_ :: PersistField a => expr (Value a) -> expr (Value (Maybe a))
- max_ :: PersistField a => expr (Value a) -> expr (Value (Maybe a))
- avg_ :: (PersistField a, PersistField b) => expr (Value a) -> expr (Value (Maybe b))
- castNum :: (Num a, Num b) => expr (Value a) -> expr (Value b)
- castNumM :: (Num a, Num b) => expr (Value (Maybe a)) -> expr (Value (Maybe b))
- coalesce :: PersistField a => [expr (Value (Maybe a))] -> expr (Value (Maybe a))
- coalesceDefault :: PersistField a => [expr (Value (Maybe a))] -> expr (Value a) -> expr (Value a)
- lower_ :: SqlString s => expr (Value s) -> expr (Value s)
- like :: SqlString s => expr (Value s) -> expr (Value s) -> expr (Value Bool)
- ilike :: SqlString s => expr (Value s) -> expr (Value s) -> expr (Value Bool)
- (%) :: SqlString s => expr (Value s)
- concat_ :: SqlString s => [expr (Value s)] -> expr (Value s)
- (++.) :: SqlString s => expr (Value s) -> expr (Value s) -> expr (Value s)
- castString :: (SqlString s, SqlString r) => expr (Value s) -> expr (Value r)
- subList_select :: PersistField a => query (expr (Value a)) -> expr (ValueList a)
- subList_selectDistinct :: PersistField a => query (expr (Value a)) -> expr (ValueList a)
- valList :: PersistField typ => [typ] -> expr (ValueList typ)
- justList :: expr (ValueList typ) -> expr (ValueList (Maybe typ))
- in_ :: PersistField typ => expr (Value typ) -> expr (ValueList typ) -> expr (Value Bool)
- notIn :: PersistField typ => expr (Value typ) -> expr (ValueList typ) -> expr (Value Bool)
- exists :: query () -> expr (Value Bool)
- notExists :: query () -> expr (Value Bool)
- set :: PersistEntity val => expr (Entity val) -> [expr (Update val)] -> query ()
- (=.) :: (PersistEntity val, PersistField typ) => EntityField val typ -> expr (Value typ) -> expr (Update val)
- (+=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val)
- (-=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val)
- (*=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val)
- (/=.) :: (PersistEntity val, PersistField a) => EntityField val a -> expr (Value a) -> expr (Update val)
- (<#) :: (a -> b) -> expr (Value a) -> expr (Insertion b)
- (<&>) :: expr (Insertion (a -> b)) -> expr (Value a) -> expr (Insertion b)
- case_ :: PersistField a => [(expr (Value Bool), expr (Value a))] -> expr (Value a) -> expr (Value a)
- toBaseId :: ToBaseId ent => expr (Value (Key ent)) -> expr (Value (Key (BaseEnt ent)))
- from :: From query expr backend a => (a -> query b) -> query b
- data Value a = Value a
- unValue :: Value a -> a
- data ValueList a = ValueList a
- data SomeValue expr where
- class ToSomeValues expr a where
- toSomeValues :: a -> [SomeValue expr]
- data InnerJoin a b = a `InnerJoin` b
- data CrossJoin a b = a `CrossJoin` b
- data LeftOuterJoin a b = a `LeftOuterJoin` b
- data RightOuterJoin a b = a `RightOuterJoin` b
- data FullOuterJoin a b = a `FullOuterJoin` b
- data OnClauseWithoutMatchingJoinException = OnClauseWithoutMatchingJoinException String
- data OrderBy
- data DistinctOn
- data Update typ
- data Insertion a
- data LockingKind
- class PersistField a => SqlString a
- class ToBaseId ent where
- type BaseEnt ent :: *
- toBaseIdWitness :: Key (BaseEnt ent) -> Key ent
- data JoinKind
- class IsJoinKind join where
- smartJoin :: a -> b -> join a b
- reifyJoinKind :: join a b -> JoinKind
- data PreprocessedFrom a
- class Esqueleto query expr backend => From query expr backend a
- class Esqueleto query expr backend => FromPreprocess query expr backend a
- when_ :: expr (Value Bool) -> () -> expr a -> (expr (Value Bool), expr a)
- then_ :: ()
- else_ :: expr a -> expr a
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.
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
:
- The simple but tedious magic of allowing tuples to be used.
- The more advanced magic of creating
JOIN
s. TheJOIN
is processed from right to left. The rightmost entity of theJOIN
is created withfromStart
. EachJOIN
step is then translated into a call tofromJoin
. In the end,fromFinish
is called to materialize theJOIN
.
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 JOIN
s without
ON
clauses (either because you didn't do any JOIN
, or
because all JOIN
s already have their own ON
clauses), a
runtime exception OnClauseWithoutMatchingJoinException
is
thrown. ON
clauses are optional when doing JOIN
s.
On the simple case of doing just one JOIN
, for example
select $from
$ \(foo `InnerJoin
` bar) -> doon
(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 on
s are applied on the reverse
order that the JOIN
s appear. For example:
select $from
$ \(foo `InnerJoin
` bar `InnerJoin
` baz) -> doon
(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) -> doon
(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) -> doon
(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) -> doon
(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] $ doorderBy
[asc foo, desc bar, desc quux] ...
Since: 2.2.4
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 Maybe
s 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 newtype
s, 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 Person
s 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 -> dowhere_
$ person^.
PersonIdin_
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 -> dowhere_
$exists
$from
$ \post -> dowhere_
(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 UPDATE
s. 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 -> dowhere_
(p^.
PersonName==.
val
"Mike"))then_
(sub_select
$from
$ \v -> do let sub =from
$ \c -> dowhere_
(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_
andthen_
is mandatory otherwise it will emit an error. - The
else_
is also mandatory, unlike the SQL statement in which if theELSE
is omitted it will return aNULL
. You can reproduce this vianothing
.
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) -> doon
(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 beNULL
into scope. Used forOUTER JOIN
s.- A
JOIN
of any other two types allowed by the innermost magic, where aJOIN
may be anInnerJoin
, aCrossJoin
, aLeftOuterJoin
, aRightOuterJoin
, or aFullOuterJoin
. TheJOINs
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 JOIN
s.
A single value (as opposed to a whole entity). You may use
(
or ^.
)(
to get a ?.
)Value
from an Entity
.
Value a |
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 |
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
).
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)
toSomeValues :: a -> [SomeValue expr] Source
data InnerJoin a b infixl 2 Source
Data type that represents an INNER JOIN
(see LeftOuterJoin
for an example).
a `InnerJoin` b infixl 2 |
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).
a `CrossJoin` b infixl 2 |
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
.
a `LeftOuterJoin` b infixl 2 |
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).
a `RightOuterJoin` b infixl 2 |
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).
a `FullOuterJoin` b infixl 2 |
IsJoinKind FullOuterJoin Source | |
(Esqueleto query expr backend, FromPreprocess query expr backend (FullOuterJoin a b)) => From query expr backend (FullOuterJoin a b) Source |
data OnClauseWithoutMatchingJoinException Source
Exception thrown whenever on
is used to create an ON
clause but no matching JOIN
is found.
data DistinctOn Source
Phantom type used by distinctOn
and don
.
Phantom type for a SET
operation on an entity of the given
type (see set
and '(=.)').
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
ForUpdate |
Since: 2.2.7 |
ForShare |
Since: 2.2.7 |
LockInShareMode |
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
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
).
toBaseIdWitness :: Key (BaseEnt ent) -> Key ent Source
The guts
(Internal) A kind of JOIN
.
InnerJoinKind | INNER JOIN |
CrossJoinKind | CROSS JOIN |
LeftOuterJoinKind | LEFT OUTER JOIN |
RightOuterJoinKind | RIGHT OUTER JOIN |
FullOuterJoinKind | FULL OUTER JOIN |
class IsJoinKind join where Source
(Internal) Functions that operate on types (that should be)
of kind JoinKind
.
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
class Esqueleto query expr backend => From query expr backend a Source
from_
(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
fromPreprocess
(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 |