co.cask.cdap.etl.api

Interface Joiner<JOIN_KEY,INPUT_RECORD,OUT>

Type Parameters:

JOIN_KEY - type of the join key

INPUT_RECORD - type of input records to be joined

OUT - type of output object

All Known Implementing Classes:

BatchJoiner

@Beta
public interface Joiner<JOIN_KEY,INPUT_RECORD,OUT>

Provides join keys on which join needs to be performed and merges the join results.

Method Summary

Methods

Modifier and Type	Method and Description
JoinConfig	getJoinConfig() Creates join configuration which holds information about required inputs which are needed to decide type of the join and produce join result.
JOIN_KEY	joinOn(String stageName, INPUT_RECORD inputRecord) Return value for the join key on which join will be performed
OUT	merge(JOIN_KEY joinKey, Iterable<JoinElement<INPUT_RECORD>> joinResult) Merges records present in joinResult and returns merged output.

Method Detail

joinOn

JOIN_KEY joinOn(String stageName,
              INPUT_RECORD inputRecord)
                throws Exception

Return value for the join key on which join will be performed

Parameters:

stageName - name of the stage to which records belongs to

inputRecord - input record to be joined

Returns:

returns join key

Throws:

Exception - if there is some error getting the join key

getJoinConfig

JoinConfig getJoinConfig()
                         throws Exception

Creates join configuration which holds information about required inputs which are needed to decide type of the join and produce join result.

Returns:

instance of JoinConfig which includes information about join to be performed

Throws:

Exception - if there is some error getting the join config

merge

OUT merge(JOIN_KEY joinKey,
        Iterable<JoinElement<INPUT_RECORD>> joinResult)
          throws Exception

Merges records present in joinResult and returns merged output.

Parameters:

joinKey - join key on which join needs to be performed

joinResult - list of JoinElement which will be used to create merged output. It will have all the records after performing join operation

Returns:

merged output created from joinResult

Throws:

Exception - if there is some error while creating merged output