How to make Execution context in Spring batch Partitioner to run in sequence - spring

Question

I have a requirement where first I have to select no of MasterRecords from table and then for each MasterRecords I will have to fetch no of child rows and for each child rows process and write chunk wise.
To do this I used Partitioner in spring batch and created master and slave steps to achieve this. Now code is working fine if I dont need to run slave step in same sequence it was added to Execution context.
But my requirement is to run slave step for each execution context in same sequence it was added in partitioner. Because until I process parent record I cannot process child records.
Using partitioner slave step is not running in same sequence. Please help me how to maintain same sequence for slave step run ?????
Is there any other way to achieve this using spring batch. any help is welcomed.
<job id="EPICSDBJob" xmlns="http://www.springframework.org/schema/batch">
<!-- Create Order Master Start -->
<step id="populateNewOrdersMasterStep" allow-start-if-complete="false"
next="populateLineItemMasterStep">
<partition step="populateNewOrders" partitioner="pdcReadPartitioner">
<handler grid-size="1" task-executor="taskExecutor" />
</partition>
<batch:listeners>
<batch:listener ref="partitionerStepListner" />
</batch:listeners>
</step>
<!-- Create Order Master End -->
<listeners>
<listener ref="epicsPimsJobListner" />
</listeners>
</job>
<step id="populateNewOrders" xmlns="http://www.springframework.org/schema/batch">
<tasklet allow-start-if-complete="true">
<chunk reader="epicsDBReader" processor="epicsPimsProcessor"
writer="pimsWriter" commit-interval="10">
</chunk>
</tasklet>
<batch:listeners>
<batch:listener ref="stepJobListner" />
</batch:listeners>
</step>
<bean id="epicsDBReader" class="com.cat.epics.sf.batch.reader.EPICSDBReader" scope="step" >
<property name="sfObjName" value="#{stepExecutionContext[sfParentObjNm]}" />
<property name="readChunkCount" value="10" />
<property name="readerDao" ref="readerDao" />
<property name="configDao" ref="configDao" />
<property name="dBReaderService" ref="dBReaderService" />
</bean>
Partitioner Method:
#Override
public Map<String, ExecutionContext> partition(int arg0) {
Map<String, ExecutionContext> result = new LinkedHashMap<String, ExecutionContext>();
List<String> sfMappingObjectNames = configDao.getSFMappingObjNames();
int i=1;
for(String sfMappingObjectName: sfMappingObjectNames){
ExecutionContext value = new ExecutionContext();
value.putString("sfParentObjNm", sfMappingObjectName);
result.put("partition:"+i, value);
i++;
}
return result;
}

Answer 1

There isn't a way to guarantee order within Spring Batch's partitioning model. The fact that the partitions are executed in parallel means that, by definition, there will be no ordering to the records processed. I think this is a case where restructuring the job a bit may help.
If your requirement is to execute the parent then execute the children, using a driving query pattern along with the partitioning would work. You'd partition along the parent records (which it looks like you're doing), then in the worker step, you'd use the parent record to drive queries and processing for the children records. That would guarantee that the child records are processed after the master one.