Encoder of some representation of a parameters product.

Has instances of Contravariant, Divisible and Monoid, which you can use to compose multiple parameters together. E.g.,

someParamsEncoder :: Params (Int64, Maybe Text)
someParamsEncoder =
  (fst >$< param (nonNullable int8)) <>
  (snd >$< param (nullable text))

As a general solution for tuples of any arity, instead of fst and snd, consider the functions of the contrazip family from the "contravariant-extras" package. E.g., here's how you can achieve the same as the above:

someParamsEncoder :: Params (Int64, Maybe Text)
someParamsEncoder =
  contrazip2 (param (nonNullable int8)) (param (nullable text))

Here's how you can implement encoders for custom composite types:

data Person = Person { name :: Text, gender :: Gender, age :: Int }

data Gender = Male | Female

personParams :: Params Person
personParams =
  (name >$< param (nonNullable text)) <>
  (gender >$< param (nonNullable genderValue)) <>
  (fromIntegral . age >$< param (nonNullable int8))

genderValue :: Value Gender
genderValue = enum genderText text where
  genderText gender = case gender of
    Male -> "male"
    Female -> "female"

No parameters. Same as mempty and conquered.

Lift a single parameter encoder, with its nullability specified, associating it with a single placeholder.

Extensional specification of nullability over a generic encoder.

Specify that an encoder produces a non-nullable value.

Specify that an encoder produces a nullable value.

Value encoder.

Encoder of BOOL values.

Encoder of INT2 values.

Encoder of INT4 values.

Encoder of INT8 values.

Encoder of FLOAT4 values.

Encoder of FLOAT8 values.

Encoder of NUMERIC values.

Encoder of CHAR values.

Note that it supports Unicode values and identifies itself under the TEXT OID because of that.

Encoder of TEXT values.

Encoder of BYTEA values.

Encoder of DATE values.

Encoder of TIMESTAMP values.

Encoder of TIMESTAMPTZ values.

Encoder of TIME values.

Encoder of TIMETZ values.

Encoder of INTERVAL values.

Encoder of UUID values.

Encoder of INET values.

Encoder of JSON values from JSON AST.

Encoder of JSON values from raw JSON.

Encoder of JSONB values from JSON AST.

Encoder of JSONB values from raw JSON.

Given a function, which maps a value into a textual enum label used on the DB side, produces an encoder of that value.

Identifies the value with the PostgreSQL's "unknown" type, thus leaving it up to Postgres to infer the actual type of the value.

The value transimitted is any value encoded in the Postgres' Text data format. For reference, see the Formats and Format Codes section of the Postgres' documentation.

Lift an array encoder into a parameter encoder.

Lift a value encoder of element into a unidimensional array encoder of a foldable value.

This function is merely a shortcut to the following expression:

(array . dimension foldl' . element)

You can use it like this:

vectorOfInts :: Value (Vector Int64)
vectorOfInts = foldableArray (nonNullable int8)

Please notice that in case of multidimensional arrays nesting foldableArray encoder won't work. You have to explicitly construct the array encoder using array.

Generic array encoder.

Here's an example of its usage:

someParamsEncoder :: Params [[Int64]]
someParamsEncoder = param (nonNullable (array (dimension foldl' (dimension foldl' (element (nonNullable int8))))))

Please note that the PostgreSQL IN keyword does not accept an array, but rather a syntactical list of values, thus this encoder is not suited for that. Use a value = ANY($1) condition instead.

Lifts a Value encoder into an Array encoder.

Encoder of an array dimension, which thus provides support for multidimensional arrays.

Accepts:

• An implementation of the left-fold operation, such as Data.Foldable.foldl', which determines the input value.
• A component encoder, which can be either another dimension or element.