Why execute query twice?

Question

I write a jsf page.there is a find botten,i drop and drag it from data control palette.then i modify it's ADFBinding method,like this:
public void find_action(ActionEvent actionEvent) {
BindingContainer bc = getBindings();
DCIteratorBinding db =
(DCIteratorBinding)bc.get("findBasRolesIter");
OperationBinding op = bc.getOperationBinding("findBasRoles");
Object ob = op.execute();
if (ob!=null){
RowImpl row = (RowImpl)db.getCurrentRow();
BasRoles role = (BasRoles)row.getDataProvider();
op = bc.getOperationBinding("findBasRoleHolders");
Map para = op.getParamsMap();
para.put("role_id", role.getRoleId().intValue());
ob = op.execute();
if (ob!=null){
op = bc.getOperationBinding("findBasRoleHrcNode");
para = op.getParamsMap();
para.put("role_id", role.getRoleId().intValue());
ob = op.execute();
the pageDEF like this
<executables>
<variableIterator id="variables"
RefreshCondition="${adfFacesContext.postback}"
Refresh="prepareModelIfNeeded">
<variable Type="java.lang.String" Name="findBasRoles_role_code"
IsQueriable="false"/>
<variable Type="java.lang.String" Name="findBasRoles_role_name"
IsQueriable="false"/>
</variableIterator>
<methodIterator id="findBasRolesIter" Binds="findBasRoles.result"
DataControl="BASjsdyFacadeLocal" RangeSize="10"
BeanClass="bas.entities.table.BasRoles"
Refresh="prepareModelIfNeeded"
RefreshCondition="${adfFacesContext.postback}"/>
<methodIterator id="findBasRoleHoldersIter"
Binds="findBasRoleHolders.result"
DataControl="BASjsdyFacadeLocal" RangeSize="10"
BeanClass="bas.entities.table.BasRoleHolders"
Refresh="prepareModelIfNeeded"
RefreshCondition="${adfFacesContext.postback}"/>
<methodIterator id="findBasRoleHrcNodeIter"
Binds="findBasRoleHrcNode.result"
DataControl="BASjsdyFacadeLocal" RangeSize="10"
BeanClass="bas.entities.table.BasRoleHrcNode"
Refresh="prepareModelIfNeeded"
RefreshCondition="${adfFacesContext.postback}"/>
</executables>
then ,when this page is running,i look the debug message from OC4J console like this
Thread(Thread[ApplicationServerThread-0,5,RequestThreadGroup])--client acquired
Thread(Thread[ApplicationServerThread-0,5,RequestThreadGroup])--SELECT ROLE_HOLDER_ID, LAST_UPDATED_BY, CREATED_BY, LAST_UPDATE_LOGIN, ENABLED_FLAG, PERSON_ID, CREATION_DATE, LAST_UPDATE_DATE, ROLE_ID FROM BAS_ROLE_HOLDERS
Thread(Thread[ApplicationServerThread-0,5,RequestThreadGroup])--client acquired
Thread(Thread[ApplicationServerThread-0,5,RequestThreadGroup])--SELECT ROLE_HRC_NODE_ID, LAST_UPDATED_BY, CREATED_BY, LAST_UPDATE_LOGIN, ENABLED_FLAG, NODE_ID, CREATION_DATE, LAST_UPDATE_DATE, ROLE_ID FROM BAS_ROLE_HRC_NODE
Thread(Thread[ApplicationServerThread-0,5,RequestThreadGroup])--client acquired
Thread(Thread[ApplicationServerThread-0,5,RequestThreadGroup])--SELECT ROLE_ID, LAST_UPDATED_BY, CREATED_BY, LAST_UPDATE_LOGIN, ENABLED_FLAG, ROLE_CODE, CREATION_DATE, LAST_UPDATE_DATE, ROLE_NAME FROM BAS_ROLES WHERE (UPPER(ROLE_NAME) LIKE '%abc')
Thread(Thread[ApplicationServerThread-0,5,RequestThreadGroup])--client acquired
Thread(Thread[ApplicationServerThread-0,5,RequestThreadGroup])--SELECT ROLE_HOLDER_ID, LAST_UPDATED_BY, CREATED_BY, LAST_UPDATE_LOGIN, ENABLED_FLAG, PERSON_ID, CREATION_DATE, LAST_UPDATE_DATE, ROLE_ID FROM BAS_ROLE_HOLDERS WHERE (ROLE_ID = 401.0)
Thread(Thread[ApplicationServerThread-0,5,RequestThreadGroup])--client acquired
Thread(Thread[ApplicationServerThread-0,5,RequestThreadGroup])--SELECT ROLE_HRC_NODE_ID, LAST_UPDATED_BY, CREATED_BY, LAST_UPDATE_LOGIN, ENABLED_FLAG, NODE_ID, CREATION_DATE, LAST_UPDATE_DATE, ROLE_ID FROM BAS_ROLE_HRC_NODE WHERE (ROLE_ID = 401.0)
the table BAS_ROLE_HRC_NODE ,BAS_ROLE_HOLDERS execute twice,
the BAS_ROLES execute once, why??

Answer 1

does anybody help?