Hi all,

I use an in memory datagrid (Coherence) as a second level cache (with hibernate 3.6 JPA)

I did a simple test on table Departments + Employees (Department load the collection of employees using Lazy loading, Employee load the department with the eager loading).

1) I did a "select * from departments"

In the log of hibernate I got

Hibernate: select department0_.DEPARTMENT_ID as DEPARTMENT1_1_, department0_.DEPARTMENT_NAME as DEPARTMENT2_1_ from DEPARTMENTS department0_
4.626: [GC [PSYoungGen: 131072K->10186K(152896K)] 131072K->10186K(502464K), 0.0181553 secs] [Times: user=0.08 sys=0.00, real=0.03 secs]
**********************************
Statistics For : model.Department
ElementCountInMemory : 28
ElementCountOnDisk : -1
Entries : {70={_version=null, _lazyPropertiesUnfetched=true, employees=70, _subclass=model.Department, name=Public Relations}, 200={_version=null, _lazyPropertiesUnfetched=true, employees=200, _subclass=model.Department, name=Operations}, 140={_version=null, _lazyPropertiesUnfetched=true, employees=140, _subclass=model.Department, name=Control And Credit}, 10={_version=null, _lazyPropertiesUnfetched=true, employees=10, _subclass=model.Department, name=Administration}, 400={_version=null, _lazyPropertiesUnfetched=true, employees=400, _subclass=model.Department, name=Stock}, 130={_version=null, _lazyPropertiesUnfetched=true, employees=130, _subclass=model.Department, name=Corporate Tax}, 220={_version=null, _lazyPropertiesUnfetched=true, employees=220, _subclass=model.Department, name=NOC}, 20={_version=null, _lazyPropertiesUnfetched=true, employees=20, _subclass=model.Department, name=Marketing}, 80={_version=null, _lazyPropertiesUnfetched=true, employees=80, _subclass=model.Department, name=Sales}, 260={_version=null, _lazyPropertiesUnfetched=true, employees=260, _subclass=model.Department, name=Recruiting}, 270={_version=null, _lazyPropertiesUnfetched=true, employees=270, _subclass=model.Department, name=Payroll}, 210={_version=null, _lazyPropertiesUnfetched=true, employees=210, _subclass=model.Department, name=IT Support}, 150={_version=null, _lazyPropertiesUnfetched=true, employees=150, _subclass=model.Department, name=Shareholder Services}, 30={_version=null, _lazyPropertiesUnfetched=true, employees=30, _subclass=model.Department, name=Purchasing}, 90={_version=null, _lazyPropertiesUnfetched=true, employees=90, _subclass=model.Department, name=Executive}, 170={_version=null, _lazyPropertiesUnfetched=true, employees=170, _subclass=model.Department, name=Manufacturing}, 100={_version=null, _lazyPropertiesUnfetched=true, employees=100, _subclass=model.Department, name=Finance}, 110={_version=null, _lazyPropertiesUnfetched=true, employees=110, _subclass=model.Department, name=Accounting}, 230={_version=null, _lazyPropertiesUnfetched=true, employees=230, _subclass=model.Department, name=IT Helpdesk}, 40={_version=null, _lazyPropertiesUnfetched=true, employees=40, _subclass=model.Department, name=Human Resources}, 160={_version=null, _lazyPropertiesUnfetched=true, employees=160, _subclass=model.Department, name=Benefits}, 50={_version=null, _lazyPropertiesUnfetched=true, employees=50, _subclass=model.Department, name=Shipping}, 250={_version=null, _lazyPropertiesUnfetched=true, employees=250, _subclass=model.Department, name=Retail Sales}, 190={_version=null, _lazyPropertiesUnfetched=true, employees=190, _subclass=model.Department, name=Contracting}, 240={_version=null, _lazyPropertiesUnfetched=true, employees=240, _subclass=model.Department, name=Government Sales}, 180={_version=null, _lazyPropertiesUnfetched=true, employees=180, _subclass=model.Department, name=Construction}, 120={_version=null, _lazyPropertiesUnfetched=true, employees=120, _subclass=model.Department, name=Treasury}, 60={_version=null, _lazyPropertiesUnfetched=true, employees=60, _subclass=model.Department, name=IT}}
HitCount : 0
MissCount : 0
PutCount : 28
SizeInMemory : -1
**********************************
**********************************
Statistics For : model.Employee
ElementCountInMemory : 0
ElementCountOnDisk : -1
Entries : {}
HitCount : 0
MissCount : 0
PutCount : 0
SizeInMemory : -1
**********************************
NB Dept : 28
**********************************

On Coherence Datagrid I saw 28 put --> OK but 56 get ? so why 2 get on each department here instead of 1 ?

2) I did a "select * from employees where employee_id = 100"

The log in hibernate

Hibernate: select employee0_.EMPLOYEE_ID as EMPLOYEE1_0_0_, employee0_.DEPARTMENT_ID as DEPARTMENT4_0_0_, employee0_.FIRST_NAME as FIRST2_0_0_, employee0_.LAST_NAME as LAST3_0_0_ from EMPLOYEES employee0_ where employee0_.EMPLOYEE_ID=?
4.356: [GC [PSYoungGen: 131072K->10608K(152896K)] 131072K->10608K(502464K), 0.0350694 secs] [Times: user=0.09 sys=0.02, real=0.05 secs]
**********************************
Statistics For : model.Department
ElementCountInMemory : 28
ElementCountOnDisk : -1
Entries : {70={_version=null, _lazyPropertiesUnfetched=true, employees=70, _subclass=model.Department, name=Public Relations}, 200={_version=null, _lazyPropertiesUnfetched=true, employees=200, _subclass=model.Department, name=Operations}, 140={_version=null, _lazyPropertiesUnfetched=true, employees=140, _subclass=model.Department, name=Control And Credit}, 10={_version=null, _lazyPropertiesUnfetched=true, employees=10, _subclass=model.Department, name=Administration}, 400={_version=null, _lazyPropertiesUnfetched=true, employees=400, _subclass=model.Department, name=Stock}, 130={_version=null, _lazyPropertiesUnfetched=true, employees=130, _subclass=model.Department, name=Corporate Tax}, 220={_version=null, _lazyPropertiesUnfetched=true, employees=220, _subclass=model.Department, name=NOC}, 20={_version=null, _lazyPropertiesUnfetched=true, employees=20, _subclass=model.Department, name=Marketing}, 80={_version=null, _lazyPropertiesUnfetched=true, employees=80, _subclass=model.Department, name=Sales}, 260={_version=null, _lazyPropertiesUnfetched=true, employees=260, _subclass=model.Department, name=Recruiting}, 270={_version=null, _lazyPropertiesUnfetched=true, employees=270, _subclass=model.Department, name=Payroll}, 210={_version=null, _lazyPropertiesUnfetched=true, employees=210, _subclass=model.Department, name=IT Support}, 150={_version=null, _lazyPropertiesUnfetched=true, employees=150, _subclass=model.Department, name=Shareholder Services}, 30={_version=null, _lazyPropertiesUnfetched=true, employees=30, _subclass=model.Department, name=Purchasing}, 90={_version=null, _lazyPropertiesUnfetched=true, employees=90, _subclass=model.Department, name=Executive}, 170={_version=null, _lazyPropertiesUnfetched=true, employees=170, _subclass=model.Department, name=Manufacturing}, 100={_version=null, _lazyPropertiesUnfetched=true, employees=100, _subclass=model.Department, name=Finance}, 110={_version=null, _lazyPropertiesUnfetched=true, employees=110, _subclass=model.Department, name=Accounting}, 230={_version=null, _lazyPropertiesUnfetched=true, employees=230, _subclass=model.Department, name=IT Helpdesk}, 40={_version=null, _lazyPropertiesUnfetched=true, employees=40, _subclass=model.Department, name=Human Resources}, 160={_version=null, _lazyPropertiesUnfetched=true, employees=160, _subclass=model.Department, name=Benefits}, 50={_version=null, _lazyPropertiesUnfetched=true, employees=50, _subclass=model.Department, name=Shipping}, 250={_version=null, _lazyPropertiesUnfetched=true, employees=250, _subclass=model.Department, name=Retail Sales}, 190={_version=null, _lazyPropertiesUnfetched=true, employees=190, _subclass=model.Department, name=Contracting}, 240={_version=null, _lazyPropertiesUnfetched=true, employees=240, _subclass=model.Department, name=Government Sales}, 180={_version=null, _lazyPropertiesUnfetched=true, employees=180, _subclass=model.Department, name=Construction}, 120={_version=null, _lazyPropertiesUnfetched=true, employees=120, _subclass=model.Department, name=Treasury}, 60={_version=null, _lazyPropertiesUnfetched=true, employees=60, _subclass=model.Department, name=IT}}
HitCount : 1
MissCount : 0
PutCount : 0
SizeInMemory : -1
**********************************
**********************************
Statistics For : model.Employee
ElementCountInMemory : 1
ElementCountOnDisk : -1
Entries : {100={lastname=King, _version=null, _lazyPropertiesUnfetched=true, firstname=Steven, department=90, _subclass=model.Employee}}
HitCount : 0
MissCount : 1
PutCount : 1
SizeInMemory : -1
**********************************
Employee [id=100, firstname=Steven, lastname=King, department Id=90]

Nice I have a hit on the department !!!

But in Coherence I saw :

On employee : 1 put (OK) but 3 get ? why 3 instead of 1 ?

On department : 0 put (OK) but 29 (28 + 1) get ? why not just 1 ?

Thank you for all...

PB