Data type to represent each named parameter.

Wrapper over name of the argument.

Operator to create NamedParams.

>>> "foo" =? (1 :: Int)
NamedParam {namedParamName = "foo", namedParamParam = Plain "1"}

So it can be used in creating the list of the named arguments:

queryNamed dbConnection [sql|
    SELECT *
    FROM users
    WHERE foo = ?foo
      AND bar = ?bar
      AND baz = ?foo
|] [ "foo" =? "fooBar"
   , "bar" =? "barVar"
   ]

PostgreSQL error type for named parameters.

Type alias for monads that can throw errors of the PgNamedError type.

This function takes query with named parameters specified like this:

SELECT name, user FROM users WHERE id = ?id

and returns either the error or the query with all names replaced by question marks ? with the list of the names in the order of their appearance.

For example:

>>> extractNames "SELECT * FROM users WHERE foo = ?foo AND bar = ?bar AND baz = ?foo"
Right ("SELECT * FROM users WHERE foo = ? AND bar = ? AND baz = ?","foo" :| ["bar","foo"])

>>> extractNames "SELECT foo FROM my_table WHERE (foo->'bar' ??| ?selectedTags);"
Right ("SELECT foo FROM my_table WHERE (foo->'bar' ?| ?);","selectedTags" :| [])

When the operator is not escaped, it's treated as a named parameter >>> extractNames "SELECT foo FROM my_table WHERE (foo->bar ?| ?selectedTags);" Left PostgreSQL named parameter error: Query contains an empty name: SELECT foo FROM my_table WHERE (foo->bar ?| ?selectedTags);

Returns the list of values to use in query by given list of Names. Throws PgNamedError if any named parameter is not specified.

Queries the database with a given query and named parameters and expects a list of rows in return.

queryNamed dbConnection [sql|
    SELECT id
    FROM table
    WHERE foo = ?foo
|] [ "foo" =? "bar" ]

Queries the database with a given row parser, Query, and named parameters and expects a list of rows in return.

Sometimes there are multiple ways to parse tuples returned by PostgreSQL into the same data type. However, it's not possible to implement multiple instances of the FromRow typeclass (or any other typeclass).

Consider the following data type:

data Person = Person
    { personName :: !Text
    , personAge  :: !(Maybe Int)
    }

We might want to parse values of the Person data type in two ways:

1. Default to parsing all fields.
2. Parse only name and age to Nothing.

If you want to have multiple instances, you need to create newtype for each case. However, in some cases it might not be convenient to deal with newtypes around large data types. So you can implement custom RowParser and use it with queryWithNamed.

queryWithNamed rowParser dbConnection [sql|
    SELECT id
    FROM table
    WHERE foo = ?foo
|] [ "foo" =? "bar" ]

Modifies the database with a given query and named parameters and expects a number of the rows affected.

executeNamed dbConnection [sql|
    UPDATE table
    SET foo = 'bar'
    WHERE id = ?id
|] [ "id" =? someId ]

Same as executeNamed but discard the number of rows affected by the given query. This function is useful when you're not interested in this number.

Helper to use named parameters. Use it to implement named wrappers around functions from postgresql-simple library. If you think that the function is useful, consider opening feature request to the postgresql-simple-named library:

• https://github.com/Holmusk/postgresql-simple-named/issues