API Docs for: 2.2.2
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MapReduce Class

Extends CommandBase
Defined in: lib/commands/mapreduce/mapreduce.js:12
Module: MR

Command used to perform a Map-Reduce query in Riak.

The Riak Map-Reduce API uses JSON for its query.

A typical map-reduce query (JSON) will look like:

{
  "inputs": "goog",
  "query": [
    {
       "map": {
         "language": "javascript",
         "source": "function(value, keyData, arg){ var data = Riak.mapValuesJson(value)[0]; var month = value.key.split('-').slice(0,2).join('-'); var obj = {}; obj[month] = data.High - data.Low; return [ obj ];}"
       }
    },
    {
       "reduce": {
         "language": "javascript",
         "source": "function(values, arg){ return [ values.reduce(function(acc, item){ for(var month in item){ if(acc[month]) { acc[month] = (acc[month] < item[month]) ? item[month] : acc[month]; } else { acc[month] = item[month]; } } return acc;  }) ];}",
         "keep": true
       }
    }
  ]
}

For more info see: Loading Data and Running MapReduce

Constructor

MapReduce

(
  • query
  • callback
  • [stream=true]
)

Defined in lib/commands/mapreduce/mapreduce.js:12

Parameters:

  • query String

    The Map-Reduce query. This is a string containing JSON.

  • callback Function

    The callback to be executed by this command.

    • err String

      An error message. Will be null if no error.

    • response Object

      the response from Riak.

      • done Boolean
        True if the entire response has been received.
      • phase Number
        The phase the response is from.
      • response Object
        The results.
    • data Object

      additional error data. Will be null if no error.

  • [stream=true] Boolean optional

    stream the results or accumulate before calling callback.

Methods

constructPbRequest

() Object protected

Inherited from CommandBase: lib/commands/commandbase.js:128

Construct and return the Riak protocol buffer message for this command. Subclasses must override this method.

Returns:

Object: a protocol buffer message builder

getCallback

() Function private

Inherited from CommandBase: lib/commands/commandbase.js:68

Fires the user's callback with the arguments passed in.

Returns:

Function: the user supplied callback

getExpectedResponseCode

() Number private

Inherited from CommandBase: lib/commands/commandbase.js:78

Returns the expected response code for this command.

Returns:

Number: the expected response code for this command.

getPbReqBuilder

() Object private

Inherited from CommandBase: lib/commands/commandbase.js:111

Returns and instance of the protocol buffer message builder for this command. This is determined via the pbRequestName passed to the constructor.

Returns:

Object: the builder for the protocol buffer message to be sent for this command

getRiakMessage

() Object private

Inherited from CommandBase: lib/commands/commandbase.js:88

Returns the encoded protobuf and message header.

Returns:

Object: object containing the header and encoded protobuf

onError

(
  • msg
  • data
)
protected

Inherited from CommandBase: lib/commands/commandbase.js:164

Called by RiakNode if an error occurs executing the command and all retries are exhausted.

Parameters:

  • msg String
    an error message
  • data Object
    additional error data

onRiakError

(
  • rpbErrorResp
)
protected

Inherited from CommandBase: lib/commands/commandbase.js:151

Called by RiakNode when a RpbErrorResp is received and all retries are exhausted. Commands may override this method.

Parameters:

  • rpbErrorResp Object
    the RpbErrorResp protocol buffer

onSuccess

(
  • pbResponseMessage
)
Boolean protected

Inherited from CommandBase: lib/commands/commandbase.js:139

Called by RiakNode when a response is received. Subclasses must override this method.

Parameters:

  • pbResponseMessage Object
    the protocol buffer received from riak

Returns:

Boolean: true if not streaming or the last response has been received, false otherwise.