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|
{-# LANGUAGE RecordWildCards #-}
{-# LANGUAGE TypeFamilies #-}
-----------------------------------------------------------------------------
-- |
-- Module : Aws.DynamoDb.Commands.Scan
-- Copyright : Soostone Inc
-- License : BSD3
--
-- Maintainer : Ozgun Ataman <ozgun.ataman@soostone.com>
-- Stability : experimental
--
-- Implementation of Amazon DynamoDb Scan command.
--
-- See: @http:\/\/docs.aws.amazon.com\/amazondynamodb\/latest\/APIReference\/API_Scan.html@
----------------------------------------------------------------------------
module Aws.DynamoDb.Commands.Scan
( Scan (..)
, scan
, ScanResponse (..)
) where
-------------------------------------------------------------------------------
import Control.Applicative
import Data.Aeson
import Data.Default
import Data.Maybe
import qualified Data.Text as T
import Data.Typeable
import qualified Data.Vector as V
-------------------------------------------------------------------------------
import Aws.Core
import Aws.DynamoDb.Core
-------------------------------------------------------------------------------
-- | A Scan command that uses primary keys for an expedient scan.
data Scan = Scan {
sTableName :: T.Text
-- ^ Required.
, sConsistentRead :: Bool
-- ^ Whether to require a consistent read
, sFilter :: Conditions
-- ^ Whether to filter results before returning to client
, sStartKey :: Maybe [Attribute]
-- ^ Exclusive start key to resume a previous query.
, sLimit :: Maybe Int
-- ^ Whether to limit result set size
, sIndex :: Maybe T.Text
-- ^ Optional. Index to 'Scan'
, sSelect :: QuerySelect
-- ^ What to return from 'Scan'
, sRetCons :: ReturnConsumption
, sSegment :: Int
-- ^ Segment number, starting at 0, for parallel queries.
, sTotalSegments :: Int
-- ^ Total number of parallel segments. 1 means sequential scan.
} deriving (Eq,Show,Read,Ord,Typeable)
-- | Construct a minimal 'Scan' request.
scan :: T.Text -- ^ Table name
-> Scan
scan tn = Scan tn False def Nothing Nothing Nothing def def 0 1
-- | Response to a 'Scan' query.
data ScanResponse = ScanResponse {
srItems :: V.Vector Item
, srLastKey :: Maybe [Attribute]
, srCount :: Int
, srScanned :: Int
, srConsumed :: Maybe ConsumedCapacity
} deriving (Eq,Show,Read,Ord)
-------------------------------------------------------------------------------
instance ToJSON Scan where
toJSON Scan{..} = object $
catMaybes
[ (("ExclusiveStartKey" .= ) . attributesJson) <$> sStartKey
, ("Limit" .= ) <$> sLimit
, ("IndexName" .= ) <$> sIndex
] ++
conditionsJson "ScanFilter" sFilter ++
querySelectJson sSelect ++
[ "TableName".= sTableName
, "ReturnConsumedCapacity" .= sRetCons
, "Segment" .= sSegment
, "TotalSegments" .= sTotalSegments
, "ConsistentRead" .= sConsistentRead
]
instance FromJSON ScanResponse where
parseJSON (Object v) = ScanResponse
<$> v .:? "Items" .!= V.empty
<*> ((do o <- v .: "LastEvaluatedKey"
Just <$> parseAttributeJson o)
<|> pure Nothing)
<*> v .: "Count"
<*> v .: "ScannedCount"
<*> v .:? "ConsumedCapacity"
parseJSON _ = fail "ScanResponse must be an object."
instance Transaction Scan ScanResponse
instance SignQuery Scan where
type ServiceConfiguration Scan = DdbConfiguration
signQuery gi = ddbSignQuery "Scan" gi
instance ResponseConsumer r ScanResponse where
type ResponseMetadata ScanResponse = DdbResponse
responseConsumer _ _ ref resp = ddbResponseConsumer ref resp
instance AsMemoryResponse ScanResponse where
type MemoryResponse ScanResponse = ScanResponse
loadToMemory = return
instance ListResponse ScanResponse Item where
listResponse = V.toList . srItems
instance IteratedTransaction Scan ScanResponse where
nextIteratedRequest request response =
case srLastKey response of
Nothing -> Nothing
key -> Just request { sStartKey = key }
|
