Opaleye.Field

Functions for working directly with Field_s.

Please note that numeric Field_ types are instances of Num, so you can use *, /, +, - on them. To create Field_s, see Opaleye.ToFields and Opaleye.SqlTypes.

Field_ used to be called Column and for technical reasons there are still a few uses of the old name around. If you see Column SqlType then you can understand it as Field SqlType, and if you see Column (Nullable SqlType) then you can understand it as FieldNullable SqlType.

Column will be fully deprecated in version 0.8.

Documentation

type family Field_ (a :: Nullability) b

The name Column will be replaced by Field in version 0.8. The Field_, Field and FieldNullable types exist to help smooth the transition. We recommend that you use Field_, Field or FieldNullable instead of Column everywhere that it is sufficient.

Instances

type Field_ 'NonNullable a

Defined in Opaleye.Field

type Field_ 'NonNullable a = Column a

type Field_ 'Nullable a

Defined in Opaleye.Field

type Field_ 'Nullable a = Column (Nullable a)

data Nullability

Constructors

NonNullable

Nullable

Instances

type A ('H NullsT :: Arr Type (TC a) k2) ('TC '(t, b) :: TC a)

Defined in Opaleye.Internal.TypeFamilies

type A ('H NullsT :: Arr Type (TC a) k2) ('TC '(t, b) :: TC a) = A ('H NullsT :: Arr Type (C a) k2) ('C t)

type A ('H WT :: Arr Type (TC a) k2) ('TC '(t, Req) :: TC a)

Defined in Opaleye.Internal.TypeFamilies

type A ('H WT :: Arr Type (TC a) k2) ('TC '(t, Req) :: TC a) = A ('H OT :: Arr Type (C a) k2) ('C t)

type A ('H OT :: Arr Type (TC a) k2) ('TC '(t, b) :: TC a)

Defined in Opaleye.Internal.TypeFamilies

type A ('H OT :: Arr Type (TC a) k2) ('TC '(t, b) :: TC a) = A ('H OT :: Arr Type (C a) k2) ('C t)

type A ('H HT :: Arr Type (TC a) k2) ('TC '(t, b) :: TC a)

Defined in Opaleye.Internal.TypeFamilies

type A ('H HT :: Arr Type (TC a) k2) ('TC '(t, b) :: TC a) = A ('H HT :: Arr Type (C a) k2) ('C t)

type A ('H HT :: Arr Type (C k2) k2) ('C '(h, o, NN) :: C k2)

Defined in Opaleye.Internal.TypeFamilies

type A ('H HT :: Arr Type (C k2) k2) ('C '(h, o, NN) :: C k2) = h

type A ('H WT :: Arr Type (TC a) Type) ('TC '(t, Opt) :: TC a)

Defined in Opaleye.Internal.TypeFamilies

type A ('H WT :: Arr Type (TC a) Type) ('TC '(t, Opt) :: TC a) = Maybe (A ('H OT :: Arr Type (C a) Type) ('C t))

type A ('H NullsT :: Arr Type (C Type) Type) ('C '(h, o, n) :: C Type)

Defined in Opaleye.Internal.TypeFamilies

type A ('H NullsT :: Arr Type (C Type) Type) ('C '(h, o, n) :: C Type) = Column (Nullable o)

type A ('H OT :: Arr Type (C Type) Type) ('C '(h, o, N) :: C Type)

Defined in Opaleye.Internal.TypeFamilies

type A ('H OT :: Arr Type (C Type) Type) ('C '(h, o, N) :: C Type) = Column (Nullable o)

type A ('H OT :: Arr Type (C Type) Type) ('C '(h, o, NN) :: C Type)

Defined in Opaleye.Internal.TypeFamilies

type A ('H OT :: Arr Type (C Type) Type) ('C '(h, o, NN) :: C Type) = Column o

type A ('H HT :: Arr Type (C Type) Type) ('C '(h, o, N) :: C Type)

Defined in Opaleye.Internal.TypeFamilies

type A ('H HT :: Arr Type (C Type) Type) ('C '(h, o, N) :: C Type) = Maybe h

type FieldNullable a = Field_ 'Nullable a

type Field a = Field_ 'NonNullable a

null :: FieldNullable a

A NULL of any type

isNull :: FieldNullable a -> Field PGBool

TRUE if the value of the field is NULL, FALSE otherwise.

matchNullable

Arguments

:: Field_ 'NonNullable b

-> (Field_ 'NonNullable a -> Field_ 'NonNullable b)

-> Field_ 'Nullable a

-> Field_ 'NonNullable b

If the Field 'Nullable a is NULL then return the Field 'NonNullable b otherwise map the underlying Field 'Nullable a using the provided function.

The Opaleye equivalent of maybe.

Will be generalized to Field_ n b in a later version.

fromNullable

Arguments

:: Field_ 'NonNullable a

-> Field_ 'Nullable a

-> Field_ 'NonNullable a

If the Field 'Nullable a is NULL then return the provided Field 'NonNullable a otherwise return the underlying Field 'NonNullable a.

The Opaleye equivalent of fromMaybe and very similar to PostgreSQL's COALESCE.

Will be generalized to Field_ n a in a later version.

toNullable :: Field_ 'NonNullable a -> Field_ 'Nullable a

Treat a field as though it were nullable. This is always safe.

The Opaleye equivalent of Just.

Will be generalized to Field_ n a in a later version.

maybeToNullable :: Maybe (Field_ 'NonNullable a) -> Field_ 'Nullable a

If the argument is Nothing return NULL otherwise return the provided value coerced to a nullable type.

Will be generalized to Maybe (Field_ n a) in a later version.

unsafeCoerceField :: Column a -> Column b