| Safe Haskell | None |
|---|---|
| Language | Haskell2010 |
Opaleye.Column
Description
Do not use. Will be deprecated in version 0.7. Use Opaleye.Field instead.
Functions for working directly with Columns.
Please note that numeric Column types are instances of Num, so
you can use *, /, +, - on them.
Column will be renamed to Field_ in version 0.7,
so you might want to use the latter as much as you can.
Synopsis
- data Column pgType
- data Nullable a
- null :: Column (Nullable a)
- isNull :: Column (Nullable a) -> Column PGBool
- matchNullable :: Column b -> (Column a -> Column b) -> Column (Nullable a) -> Column b
- fromNullable :: Column a -> Column (Nullable a) -> Column a
- toNullable :: Column a -> Column (Nullable a)
- maybeToNullable :: Maybe (Column a) -> Column (Nullable a)
- unsafeCast :: String -> Column a -> Column b
- unsafeCoerceColumn :: Column a -> Column b
- unsafeCompositeField :: Column a -> String -> Column b
- null :: Column (Nullable a)
- isNull :: Column (Nullable a) -> Column PGBool
- matchNullable :: Column b -> (Column a -> Column b) -> Column (Nullable a) -> Column b
- fromNullable :: Column a -> Column (Nullable a) -> Column a
- toNullable :: Column a -> Column (Nullable a)
- maybeToNullable :: Maybe (Column a) -> Column (Nullable a)
- joinNullable :: Column (Nullable (Nullable a)) -> Column (Nullable a)
Column
A column of a Query, of type pgType. For example Column
PGInt4 is an int4 column and a Column PGText is a text
column.
Do not use the Show instance of Column. It is considered
deprecated and will be removed in version 0.7.
The name Column will be replaced by Field in version 0.7.
There already exists a Field type family to help smooth the
transition. We recommend that you use Field_, Field or
FieldNullable instead of Column everywhere that it is
sufficient.
Instances
Working with NULL
Only used within a Column, to indicate that it can be NULL.
For example, a Column (Nullable PGText) can be NULL but a
Column PGText cannot.
Instances
| Default ToFields haskell (Column sql) => Default ToFields (Maybe haskell) (Column (Nullable sql)) Source # | |
| Default NullMaker (Column a) (Column (Nullable a)) Source # | |
| Default NullMaker (Column (Nullable a)) (Column (Nullable a)) Source # | |
| IsSqlType a => IsSqlType (Nullable a) Source # | |
Defined in Opaleye.Internal.PGTypes Methods showPGType :: proxy (Nullable a) -> String Source # showSqlType :: proxy (Nullable a) -> String Source # | |
| PGOrd a => PGOrd (Nullable a) Source # | |
Defined in Opaleye.Order | |
| DefaultFromField a b => QueryRunnerColumnDefault (Nullable a) (Maybe b) Source # | |
Defined in Opaleye.Internal.RunQuery | |
| type Map Nulled (Column (Nullable a)) Source # | |
isNull :: Column (Nullable a) -> Column PGBool Source #
TRUE if the value of the column is NULL, FALSE otherwise.
matchNullable :: Column b -> (Column a -> Column b) -> Column (Nullable a) -> Column b Source #
If the Column (Nullable a) is NULL then return the Column b
otherwise map the underlying Column a using the provided
function.
The Opaleye equivalent of maybe.
fromNullable :: Column a -> Column (Nullable a) -> Column a Source #
If the Column (Nullable a) is NULL then return the provided
Column a otherwise return the underlying Column a.
The Opaleye equivalent of fromMaybe and very similar
to PostgreSQL's COALESCE.
toNullable :: Column a -> Column (Nullable a) Source #
Treat a column as though it were nullable. This is always safe.
The Opaleye equivalent of Just.
maybeToNullable :: Maybe (Column a) -> Column (Nullable a) Source #
If the argument is Nothing return NULL otherwise return the
provided value coerced to a nullable type.
Unsafe operations
unsafeCast :: String -> Column a -> Column b Source #
Cast a column to any other type. Implements Postgres's :: or
CAST( ... AS ... ) operations. This is safe for some
conversions, such as uuid to text.
unsafeCoerceColumn :: Column a -> Column b Source #
Treat a Column as though it were of a different type. If such
a treatment is not valid then Postgres may fail with an error at
SQL run time.
Entire module
isNull :: Column (Nullable a) -> Column PGBool Source #
TRUE if the value of the column is NULL, FALSE otherwise.
matchNullable :: Column b -> (Column a -> Column b) -> Column (Nullable a) -> Column b Source #
If the Column (Nullable a) is NULL then return the Column b
otherwise map the underlying Column a using the provided
function.
The Opaleye equivalent of maybe.
fromNullable :: Column a -> Column (Nullable a) -> Column a Source #
If the Column (Nullable a) is NULL then return the provided
Column a otherwise return the underlying Column a.
The Opaleye equivalent of fromMaybe and very similar
to PostgreSQL's COALESCE.
toNullable :: Column a -> Column (Nullable a) Source #
Treat a column as though it were nullable. This is always safe.
The Opaleye equivalent of Just.