-- | Render an action that must be done on a table.
showAlterTable :: DBName -> AlterTable -> String
showAlterTable table (AddUniqueConstraint cname cols) = concat
    [ "ALTER TABLE "
    , escapeDBName table
    , " ADD CONSTRAINT "
    , escapeDBName cname
    , " UNIQUE("
    , intercalate "," $ map escapeDBName' cols
    , ")"
    ]
    where
      escapeDBName' (name, (FTTypeCon _ "Text"      ), maxlen) = escapeDBName name ++ "(" ++ show maxlen ++ ")"
      escapeDBName' (name, (FTTypeCon _ "String"    ), maxlen) = escapeDBName name ++ "(" ++ show maxlen ++ ")"
      escapeDBName' (name, (FTTypeCon _ "ByteString"), maxlen) = escapeDBName name ++ "(" ++ show maxlen ++ ")"
      escapeDBName' (name, _                         , _) = escapeDBName name
showAlterTable :: DBName -> AlterTable -> String
showAlterTable table (AddUniqueConstraint cname cols) = concat
    [ "ALTER TABLE "
    , escapeDBName table
    , " ADD CONSTRAINT "
    , escapeDBName cname
    , " UNIQUE("
    , intercalate "," $ map escapeDBName' cols
    , ")"
    ]
    where
      escapeDBName' (name, (FTTypeCon _ "Text"      ), maxlen) = escapeDBName name ++ "(" ++ show maxlen ++ ")"
      escapeDBName' (name, (FTTypeCon _ "String"    ), maxlen) = escapeDBName name ++ "(" ++ show maxlen ++ ")"
      escapeDBName' (name, (FTTypeCon _ "ByteString"), maxlen) = escapeDBName name ++ "(" ++ show maxlen ++ ")"
      escapeDBName' (name, _                         , _) = escapeDBName name
showAlterTable table (AddUniqueConstraint cname cols) = concat
    [ "ALTER TABLE "
    , escapeDBName table
    , " ADD CONSTRAINT "
    , escapeDBName cname
    , " UNIQUE("
    , intercalate "," $ map escapeDBName' cols
    , ")"
    ]
    where
      escapeDBName' (name, (FTTypeCon _ "Text"      ), maxlen) = escapeDBName name ++ "(" ++ show maxlen ++ ")"
      escapeDBName' (name, (FTTypeCon _ "String"    ), maxlen) = escapeDBName name ++ "(" ++ show maxlen ++ ")"
      escapeDBName' (name, (FTTypeCon _ "ByteString"), maxlen) = escapeDBName name ++ "(" ++ show maxlen ++ ")"
      escapeDBName' (name, _                         , _) = escapeDBName name