| layout | title | categories | parent | weight |
|---|---|---|---|---|
post |
Parent Child Relationship |
SBP |
modeling-your-data.html |
100 |
{% summary %}Constructing Parent-Child Relationships with GigaSpaces Data-Grid{% endsummary %}
In some cases, you might want to store objects within the space that include references to other space objects -- i.e. an object graph. With such object relationships, you might want to fetch a parent object that is associated with a child object(s) holds a specific data (join).
{% tip %} See the Modeling your data section for details about when you should construct strong relationship between parent-child objects (embed) and when you should not embed child objects within their parent but have the ID of child objects placed within the parent object. {% endtip %}
The example below demonstrates how ID operations handle relationships between objects. This example using the readByIds batch operation to retrieve multiple space objects using on their ID:
{% highlight java %} ReadByIdsResult childrenObjResult = space.readByIds(Child.class,childrenIDs); {% endhighlight %}
The example writes 10000 parent-child graphs into the space. Two types of graphs will be created with this example:
- 5 graphs with the following values for the child objects:
0,1,2,3,4,5,6,7,8,9. - 9955 graphs with the following values for the child objects:
0,10,20,30,40,50,60,70,80,90.
The example demonstrates a simple approach locating all the parent objects that have two child objects with values of 1 and 2 -- effectively a join operation using ID operations. This will return 5 matching graphs.
{% tip %} The full example source code can be downloaded here. {% endtip %}
{% inittab Space-Level Storage Type|top %} {% tabcontent Child Class %} {% highlight java %} package com.j_spaces.examples.parentchild;
import com.gigaspaces.annotation.pojo.SpaceClass; import com.gigaspaces.annotation.pojo.SpaceId; import com.gigaspaces.annotation.pojo.SpaceIndex; import com.gigaspaces.annotation.pojo.SpaceRouting; import com.gigaspaces.metadata.index.SpaceIndexType; ;
@SpaceClass public class Child {
private String parentID;
private Long data;
private String id;
public Child(){}
public Child(String id, String _parentID)
{
this.parentID = _parentID;
this.id = id;
}
public String toString()
{
return "ID:" + id + " data:" + data;
}
@SpaceIndex(type=SpaceIndexType.BASIC)
public Long getData() {
return data;
}
public void setData(Long data) {
this.data= data;
}
@SpaceId (autoGenerate = false)
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
@SpaceIndex(type=SpaceIndexType.BASIC)
@SpaceRouting
public String getParentID() {
return parentID;
}
public void setParentID(String parentID) {
this.parentID = parentID;
}
} {% endhighlight %} {%endtabcontent%}
{% tabcontent Parent class %}
{% highlight java %} package com.j_spaces.examples.parentchild;
import java.rmi.RemoteException;
import org.openspaces.core.GigaSpace;
import net.jini.core.entry.UnusableEntryException; import net.jini.core.transaction.TransactionException;
import com.gigaspaces.annotation.pojo.SpaceClass; import com.gigaspaces.annotation.pojo.SpaceId; import com.gigaspaces.annotation.pojo.SpaceIndex; import com.gigaspaces.annotation.pojo.SpaceRouting; import com.gigaspaces.client.ReadByIdsResult; import com.gigaspaces.metadata.index.SpaceIndexType;
@SpaceClass public class Parent {
private String childrenIDs[];
private transient Child children[];
private Long data;
private String id;
static final String ChildClassName = Child.class.getName();
public Parent() {
}
public Parent(String id) {
this.id = id;
}
public String _getChildrenDetails(GigaSpace space) throws
RemoteException,
TransactionException,
UnusableEntryException
{
String ret="";
Child[] childs = _getChildren(space);
for (int i=0;i<childs.length ; i++)
{
ret = ret + childs[i].toString() + " | ";
}
return ret;
}
public Child[] _getChildren(GigaSpace space) throws
RemoteException,
TransactionException,
UnusableEntryException
{
if (children == null)
{
ReadByIdsResult<Child> childrenObjResult = space.readByIds(Child.class,childrenIDs);
children = childrenObjResult.getResultsArray();
}
return children;
}
public String _getChildrenIDs()
{
String res ="";
for (int i=0 ; i< childrenIDs.length; i++)
{
res =res +childrenIDs[i] + "\n";
}
return res;
}
@SpaceIndex(type=SpaceIndexType.BASIC)
public Long getData() {
return data;
}
public void setData(Long data) {
this.data = data;
}
public String[] getChildrenIDs() {
return childrenIDs;
}
public void setChildrenIDs(String[] _childrenIDs ) {
this.childrenIDs = _childrenIDs ;
}
@SpaceId(autoGenerate=false)
@SpaceRouting
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
} {% endhighlight %}
{%endtabcontent%}
{% tabcontent Application %}
{% highlight java %} package com.j_spaces.examples.parentchild;
import java.rmi.RemoteException; import java.util.HashSet; import java.util.Set;
import org.openspaces.core.GigaSpace; import org.openspaces.core.GigaSpaceConfigurer; import org.openspaces.core.space.UrlSpaceConfigurer; import net.jini.core.entry.UnusableEntryException; import net.jini.core.transaction.TransactionException; import com.gigaspaces.client.ReadByIdsResult;
public class ParentChildMain {
static GigaSpace space;
static int max_graphs = 10000;
static int matching_graphs = 5;
public static void main(String[] args) {
try {
UrlSpaceConfigurer urlSpaceConfigurer = new UrlSpaceConfigurer("/./mySpace");
space = new GigaSpaceConfigurer(urlSpaceConfigurer.space()).gigaSpace();
System.out.println("Write " + max_graphs+ " parent/child graphs.\nWe will have 2 types of graphs:" +
"\n" + matching_graphs+
" graphs that got the following values for the child objects:0,1,2,3,4,5,6,7,8,9" +
"\nand another " +(max_graphs - matching_graphs) +
" graphs with the following values for the child objects:0,10,20,30,40,50,60,70,80,90");
go();
} catch (Exception e) {
e.printStackTrace();
} }
static public void go() throws Exception
{
for (int i = 0; i < max_graphs; i++) {
Parent parent = new Parent(i +"");
Child _children[] = new Child[10];
String _childrenIDs[] = new String[10];
for (int j = 0; j < 10; j++) {
_children[j] = new Child(i + "_" + j,parent.getId());
if (i% (max_graphs/matching_graphs) ==0)
_children[j].setData(new Long(j));
else
_children[j].setData (new Long(j * 10));
_childrenIDs[j] = _children[j].getId();
}
parent.setChildrenIDs (_childrenIDs);
space.write(parent);
space.writeMultiple(_children);
}
findMatchingGraph(1,2);
findMatchingGraph(3,4);
findMatchingGraph(5,6);
findMatchingGraph(7,8);
}
static void findMatchingGraph(long value1, long value2) throws Exception
{
System.out.println("-----------------------------------------------------------------");
System.out.println("Find all the parent objects that got 2 child objects with values " +
value1 +" and " + value2+ "");
System.out.println("Both child objects have the same parent object");
Long startTime = System.nanoTime();
Object childrenResults1[] = findChildrenByValue(new Long(value1));
Set<String> parentIDs1 = getParentIDsSet(childrenResults1);
Object childrenResults2[] = findChildrenByValue(new Long(value2));
Set<String> parentIDs2 = getParentIDsSet(childrenResults2);
Set<String> resultSet = AND(parentIDs1, parentIDs2);
Parent parents[] = getParentsfromIDs(resultSet);
Long endTime = System.nanoTime();
System.out.println(" --->> Found " + parents.length +
" matching Parent objects in " + (double)(((double)endTime - (double)startTime)/1000) + " micro second");
for (int i = 0; i < parents.length; i++) {
System.out.println("Found Parent Object:" + parents[i]
+ " - ID:" + parents[i].getId() + " - His children objects are:\n\t"
+ parents[i]._getChildrenDetails(space));
}
}
static public Object[] findChildrenByValue(Long value) throws
RemoteException,
TransactionException,
UnusableEntryException {
Child childTemplate = new Child();
childTemplate.setData(value);
return space.readMultiple(childTemplate , Integer.MAX_VALUE);
}
static public Set<String> getParentIDsSet(Object entries[]) {
HashSet<String> result = new HashSet<String>();
for (int i = 0; i < entries.length; i++) {
result.add(((Child) entries[i]).getParentID());
}
return result;
}
static public Parent[] getParentsfromIDs(Set ids) throws
UnusableEntryException,
RemoteException,
TransactionException
{
ReadByIdsResult<Parent> parentObjResult = space.readByIds(Parent.class,ids.toArray());
return parentObjResult.getResultsArray();
}
// find union between set1 and set2
static public Set<String> AND(Set<String> set1, Set<String> set2) {
HashSet<String> result = new HashSet<String>(set1);
result.retainAll(set2);
return result;
}
} {% endhighlight %}
{%endtabcontent%}
{%endinittab%}
{% highlight java %} Write 10000 parent/child graphs. We will have 2 types of graphs: 5 graphs that got the following values for the child objects:0,1,2,3,4,5,6,7,8,9 and another 9995 graphs with the following values for the child objects:0,10,20,30,40,50,60,70,80,90
Find all the parent objects that got 2 child objects with values 1 and 2 Both child objects have the same parent object --->> Found 5 matching Parent objects in 623.38 micro second Found Parent Object:com.j_spaces.examples.parentchild.Parent@335053 - ID:8000 - His children objects are: ID:8000_0 data:0 | ID:8000_1 data:1 | ID:8000_2 data:2 | .... Found Parent Object:com.j_spaces.examples.parentchild.Parent@1c0cd80 - ID:0 - His children objects are: ID:0_0 data:0 | ID:0_1 data:1 | ID:0_2 data:2 | ... Found Parent Object:com.j_spaces.examples.parentchild.Parent@f3c5c4 - ID:6000 - His children objects are: ID:6000_0 data:0 | ID:6000_1 data:1 | ID:6000_2 data:2 | ... Found Parent Object:com.j_spaces.examples.parentchild.Parent@3ce725 - ID:4000 - His children objects are: ID:4000_0 data:0 | ID:4000_1 data:1 | ID:4000_2 data:2 | ... Found Parent Object:com.j_spaces.examples.parentchild.Parent@6b6ac8 - ID:2000 - His children objects are: ID:2000_0 data:0 | ID:2000_1 data:1 | ID:2000_2 data:2 | ... {% endhighlight %}