2:17 a.m.
Steve,
Thank you for your reply - I figure this may turn into a feature request
rather than a bug per-se.
Here is the Hibernate Doco I was referring to:
http://www.hibernate.org/hib_docs/v3/reference/en/html/filters.html#obje
ctstate-filters
I am storing a copy of the pretty much the entire database with
effective date filters as per the example.
The basic problem is that effective date filters (asOfDate in the
example) work fine if you get everything in one query - the association
between the entities becomes One-To-One, Many-To-One or whatever ONCE
the filters have been applied. In the example you may have many
different versions of the same department and many different versions of
the same employee - but for a given asOfDate there is only one
department record that links to a given employee.
BUT if you attempt to lazy load the properties - it fails because the
SQL generated from the load in EntityJoinWalker explicitly excludes
filters - even if they are active.
With relatively simple changes to EntityJoinWalker (to generate the
correct SQL) and QueryParameters (to set the filter parameters) I have
been able to remedy the problem for us - albeit with explicit
assumptions that are only valid for our database. It would be fantastic
if Hibernate supported historical data - with effective dates not just
on rows but across associations - as this is a common use case for
historical data - and I don't believe it would be difficult to implement
- all it needs is to include filters when processing unique keys (as
opposed to IDs). The historical associations are then based on these
unique keys. (Unique keys here - in the sense that they are unique
for a given point in time)
Thank you for your time - would you like me to raise this as a feature
request?
Alex
-----Original Message-----
From: Steve Ebersole [mailto:steve.ebersole@jboss.com]
Sent: Saturday, 9 September 2006 12:25 AM
To: Alex Bacon
Cc: hibernate-dev(a)lists.jboss.org
Subject: RE: Major issue with Hibernate Filters
You need to point me to where we ever created an example of filter usage
"in order to achieve uniqueness". That is expressly *not* a usage of
filters; filters by definition cannot change the multiplicity of an
association.
-----Original Message-----
From: hibernate-dev-bounces(a)lists.jboss.org
[mailto:hibernate-dev-bounces@lists.jboss.org] On Behalf Of Alex Bacon
Sent: Friday, September 08, 2006 4:51 AM
To: hibernate-dev(a)lists.jboss.org
Subject: Major issue with Hibernate Filters
Hibernate developers,
I'm afraid the forums had nothing about this issue - and I believe I
have found the bit of Hibernate coding causing the problem:
I have spent the last few weeks trying to get the Filters to work as per
the example in the Hibernate reference manual - the problem is that
filters are only currently applied for queries - they are not applied
when lazy loading entities - this causes major errors when using the
historical filters as per your example that need the filters in order to
achieve uniqueness. (I cannot realistically eager load everything in
the database!
Here is the bit of code from AbstractEntityLoader that appears to be
causing the problem:
public void processFilters(String sql, SessionImplementor session) {
if ( session.getEnabledFilters().size()==0 ||
sql.indexOf(ParserHelper.HQL_VARIABLE_PREFIX)<0 ) {
// HELLA IMPORTANT OPTIMIZATION!!!
processedPositionalParameterValues =
getPositionalParameterValues();
processedPositionalParameterTypes =
getPositionalParameterTypes();
processedSQL = sql;
}
else {
Do you agree this is an issue - and if so - I take it I should raise it
as a JIRA issue. If not - can you suggest a workaround?
Alex
-----Original Message-----
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