57 lines
1.7 KiB
Haskell
57 lines
1.7 KiB
Haskell
{-# LANGUAGE DeriveAnyClass #-}
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{-# LANGUAGE DeriveGeneric #-}
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module PostgREST.DbStructure.Relationship
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( Cardinality(..)
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, Relationship(..)
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, Junction(..)
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, RelationshipsMap
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) where
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import qualified Data.Aeson as JSON
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import qualified Data.HashMap.Strict as M
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import PostgREST.DbStructure.Identifiers (FieldName,
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QualifiedIdentifier, Schema)
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import Protolude
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-- | Relationship between two tables.
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data Relationship = Relationship
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{ relTable :: QualifiedIdentifier
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, relForeignTable :: QualifiedIdentifier
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, relIsSelf :: Bool -- ^ Whether is a self relationship
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, relCardinality :: Cardinality
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, relTableIsView :: Bool
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, relFTableIsView :: Bool
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}
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deriving (Eq, Ord, Generic, JSON.ToJSON)
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-- | The relationship cardinality
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-- | https://en.wikipedia.org/wiki/Cardinality_(data_modeling)
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-- TODO: missing one-to-one
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data Cardinality
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= O2M {relCons :: FKConstraint, relColumns :: [(FieldName, FieldName)]}
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-- ^ one-to-many
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| M2O {relCons :: FKConstraint, relColumns :: [(FieldName, FieldName)]}
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-- ^ many-to-one
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| M2M Junction
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-- ^ many-to-many
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deriving (Eq, Ord, Generic, JSON.ToJSON)
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type FKConstraint = Text
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-- | Junction table on an M2M relationship
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data Junction = Junction
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{ junTable :: QualifiedIdentifier
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, junConstraint1 :: FKConstraint
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, junConstraint2 :: FKConstraint
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, junColumns1 :: [(FieldName, FieldName)]
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, junColumns2 :: [(FieldName, FieldName)]
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}
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deriving (Eq, Ord, Generic, JSON.ToJSON)
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-- | Key based on the source table and the foreign table schema
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type RelationshipsMap = M.HashMap (QualifiedIdentifier, Schema) [Relationship]
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