Database.HaskellDB.FieldType

Defines the types of database columns, and functions for converting these between HSQL and internal formats

Documentation

type FieldDesc = (FieldType, Bool)

The type and nullable flag of a database column

data FieldType

A database column type

Constructors

StringT

IntT

IntegerT

DoubleT

BoolT

CalendarTimeT

LocalTimeT

BStrT Int

Instances

Eq FieldType

Ord FieldType

Read FieldType

Show FieldType

toHaskellType :: FieldType -> String

class ExprType e where

Class which retrieves a field description from a given type. Instances are provided for most concrete types. Instances for Maybe automatically make the field nullable, and instances for all (Expr a) types where a has an ExprType instance allows type information to be recovered from a given column expression.

Methods

fromHaskellType :: e -> FieldDesc

Instances

ExprType Bool

ExprType Double

ExprType Int

ExprType Integer

ExprType String

ExprType CalendarTime

ExprType LocalTime

ExprType a => ExprType (Maybe a)

Size n => ExprType (BoundedString n)

ExprType a => ExprType (Expr a)

ExprType a => ExprType (Rel a)

class ExprTypes r where

Class which returns a list of field descriptions. Gets the descriptions of all columns in a Record/query. Most useful when the columns associated with each field in a (Rel r) type must be recovered. Note that this occurs at the type level only and no values are inspected.

Methods

fromHaskellTypes :: r -> [FieldDesc]

Instances

ExprTypes RecNil

ExprTypes r => ExprTypes (Record r)

ExprTypes r => ExprTypes (Rel r)

(ExprType e, ExprTypes r) => ExprTypes (RecCons f e r)

queryFields :: (ShowLabels r, ExprTypes r) => Query (Rel r) -> [(String, FieldDesc)]

Given a query, returns a list of the field names and their types used by the query. Useful for recovering field information once a query has been built up.