3.6 Group Aggregation Question

Question

I am trying to achieve a sql group by sort of behavior with coherence 3.6. I have achieved some success by using the following code.
public InvocableMap.EntryAggregator getAggregationCriteria()
BigDecimalSum agg1 = new BigDecimalSum("getTradeDateMVLocal");
BigDecimalSum agg2 = new BigDecimalSum("getTradeDateCashLocal");
BigDecimalSum agg3 = new BigDecimalSum("getCostLocal");
BigDecimalSum agg4 = new BigDecimalSum("getInterestUnrealizedLocal");
CompositeAggregator compAgg =
CompositeAggregator.createInstance(new InvocableMap.EntryAggregator[]
{agg1, agg2, agg3, agg4});
ChainedExtractor cr1 = new ChainedExtractor("getKey.getAccountName");
ChainedExtractor cr2 = new ChainedExtractor("getKey.getCurrency");
ValueExtractor[] extractors = new ValueExtractor[2];
extractors[0] = cr1;
extractors[1] = cr2;
MultiExtractor multiEx = new MultiExtractor(extractors);
GroupAggregator gpa = GroupAggregator.createInstance(multiEx, compAgg);
return gpa;
once the GroupAggregator is constructed I pass it to the namedcache.aggregate method using the following wrapper method.
public LiteMap aggregate(NamedCache cache, Filter filter, InvocableMap.EntryAggregator aggregationCriteria)
LiteMap map = (LiteMap) cache.aggregate(filter, aggregationCriteria);
return map;
the issue is that in a multi-node environment not all the data is aggregated.
for example if i have a single node and i run my aggregation code just in that node i get the expected number of grouped items. in a multi node scenario it ends up with lesser items. now the columns that i am grouping by are part of my composite key for the cache. the implementation of my key class is as follows.
package com.sac.dream.model;
import com.sac.dream.core.model.GridEntityKey;
import com.sac.dream.util.externalization.ObjectReader;
import com.sac.dream.util.externalization.ObjectWriter;
import com.tangosol.net.cache.KeyAssociation;
import javax.persistence.Embeddable;
import javax.persistence.Transient;
import java.io.IOException;
* Created by IntelliJ IDEA.
* User: ahmads
* Date: Jul 28, 2010
* Time: 1:54:45 PM
* To change this template use File | Settings | File Templates.
@Embeddable
public class GenevaValuationKey extends GridEntityKey implements KeyAssociation
private static final long serialVersionUID = 1L;
private String accountName;
private String currency;
private Long uid;
public GenevaValuationKey(Long uid)
this.uid = uid;
public GenevaValuationKey()
@Transient
public Object getAssociatedKey()
int hash = 1;
hash = hash * 31 + getAccountName().hashCode();
hash = hash * 31 + getCurrency().hashCode();
return hash;
public void setAssociatedKey(Object value)
public Long getUid() {
return uid;
public void setUid(Long uid) {
this.uid = uid;
@Override
public String toString()
return "GenevaValuationKey::uid:" + this.uid;
@Override
public boolean equals(Object o)
//if(this == o) return true;
//if (o == null || getClass() != o.getClass()) return false;
GenevaValuationKey that = (GenevaValuationKey) o;
if(this.getAccountName().equals(that.getAccountName()) && this.getCurrency().equals(that.getCurrency()) && this.uid == that.uid)
return true;
else
return false;
@Override
public int hashCode()
int hash = 1;
hash = hash * 31 + getAccountName().hashCode();
hash = hash * 31 + getCurrency().hashCode();
hash = hash * 31 + uid.hashCode();
return hash;
@Override
     public int compareTo(GridEntityKey o)
return this.uid.compareTo(((GenevaValuationKey) o).getUid());
@Override
public final void readObject(ObjectReader reader) throws IOException
try
this.setAccountName(reader.readString());
this.setCurrency(reader.readString());
     this.uid = reader.readLong();
catch(IOException e)
throw new RuntimeException(e);
@Override
     public final void writeObject(ObjectWriter writer) throws IOException
try
writer.writeString(this.getAccountName());
writer.writeString(this.getCurrency());
     writer.writeLong(this.uid);
catch(IOException e)
throw new RuntimeException(e);
public String getAccountName() {
return accountName;
public void setAccountName(String accountName) {
this.accountName = accountName;
public String getCurrency() {
return currency;
public void setCurrency(String currency) {
this.currency = currency;
i implemented the keyassociation assuming that i need to make sure that for a certain group all the rows within that group need to exist on the same node. there might be something wrong with that implementation.
thanks

Answer 1

rehevkor5 wrote:
Yeah apparently you're not supposed to call readRemainder or writeRemainder from within the PortableObject methods, too bad the documentation does not mention this.
Here is a better idea of what a subclass's PortableObject methods should look like:
@Override
public void readExternal(PofReader in) throws IOException {
super.readExternal(in.createNestedPofReader(0));
myObj = (MyType) in.readObject(1);
@Override
public void writeExternal(PofWriter out) throws IOException {
super.writeExternal(out.createNestedPofWriter(0));
out.writeObject(1, myObj);
}Since you cannot read or write the remainder, the way that you support PortableObjects that need to evolve is by implementing the Evolvable interface. Coherence will detect that your object is an instanceof Evolvable, and will handle reading/writing the remainder/futureData and dataVersion for you.Yep. Otherwise, if you have handled the remainder in a PortableObject, you would not be able to sensibly override that method which handled the remainder.
Best regards,
Robert