Before anything, i must say this first: This table design is not my decision. We protest but to no avail, so please don't tell me, don't create a table like that.
We have a database with each table have a flag. This flag used to indicate which environment this row belong to, production or test data.
For server side, we have one variable which currently stored in ThreadLocal to indicate which environment this request belong to, same value as the flag in database.
Our requirement is that if my request belong to test environment then we must select only record belong to this environment. We would need to add a condition to every query we made to database, something like:
SELECT t FROM TABLE t WHERE t.flag = :environment
But we have to update every single query, update every object to set this flag before insert/update into database. This will require a lot of effort as our system already built long ago, not on progress. Also this will bring a lots of risk if someone forgot to add this to any new query.
So is there anyway to insert a condition to check this flag value for every query without have to manually edit the query string? Like an interceptor or something to put this condition in?
Which JPA provider?
With Hibernate, you could try using a #Filter.
Multitenancy could be another option, but probably an overkill in your scenario.
Finally, since you flagged the question with Oracle, perhaps the easiest approach would be to provide dedicated schemas (per environment) with views for every single table in your db, filtered by the flag column. Not sure if you're allowed to do that, though.
With some of the above, you would need a global entity listener to populate the flag field of your entities before they are persisted.
Related
I'm trying to find some nice work arounds for the issues of computed columns in code first. Specifically, I have a number of CreatedAt datetime columns that need to be set to getdate().
I've looked at doing this via the POCO constructors, but to do that I must remove the Computed option (or it won't persist the data), however, there is no easy to way ensure the column is only set if we are inserting a record. So this would overwrite the CreatedAt each time we update.
I'm looking to create an alter script that can be called after the DropCreate that would go through and alter various columns to include the default value of getdate().
Is there an event to hook into something like OnDropCreateCompleted where I could then run additional SQL
What would be the best way handle the alter script? I am thinking just sending raw sql to the server that would run.
Is there another way to handle the getdate() issue that might be more graceful and more inline with code first that I'm missing?
Thanks
You can just make custom initializer derived from your desired one and override Seed method where you can execute any SQL you want to use - here is some example for creating such initializer.
If you are using migrations you can just the custom SQL to Up method.
I have an entity with several fields, but on one view i want to only edit one of the fields. for example... I have a user entity, user has, id, name, address, username, pwd, and so on. on one of the views i want to be able to change the pwd(and only the pwd). so the view only knows of the id and sends the pwd. I want to update my entity without loading the rest of the fields(there are many many more) and changing the one pwd field and then saving them ALL back to the database. has anyone tried this. or know where i can look. all help is greatly appreciated.
Thx in advance.
PS
i should have given more detail. im using hibernate, roo is creating my entities. I agree that each view should have its own entity, problem is, im only building controllers, everything was done before. we were finders from the service layer, but we wanted to use some other finders, they seemed to not be accessible through the service layer, the decision was made to blow away the service layer and just interact with the entities directly (through the finders), the UserService.update(user) is no longer an option. i have recently found a User.persist() and a User.merge(), does the merge update all the fields on the object or only the ones that are not null, or if i want one to now be null how would it know the difference?
Which technologies except Spring are you using?
First of all have separate DTOs for every view, stripped only to what's needed. One DTO for id+password, another for address data, etc. Remember that DTOs can inherit from each other, so you can avoid duplication. And never pass business/ORM entities directly to view. It is too risky, leaks in some frameworks might allow users to modify fields which you haven't intended.
After the DTO comes back from the view (most web frameworks work like this) simply load the whole entity and fill only the fields that are present in the DTO.
But it seems like it's the persistence that is troubling you. Assuming you are using Hibernate, you can take advantage of dynamic-update setting:
dynamic-update (optional - defaults to false): specifies that UPDATE SQL should be generated at runtime and can contain only those columns whose values have changed.
In this case you are still loading the whole entity into memory, but Hibernate will generate as small UPDATE as possible, including only modified (dirty) fields.
Another approach is to have separate entities for each use-case/view. So you'll have an entity with only id and password, entity with only address data, etc. All of them are mapped to the same table, but to different subset of columns. This easily becomes a mess and should be treated as a last resort.
See the hibernate reference here
For persist()
persist() makes a transient instance persistent. However, it does not guarantee that the
identifier value will be assigned to the persistent instance immediately, the assignment
might happen at flush time. persist() also guarantees that it will not execute an INSERT
statement if it is called outside of transaction boundaries. This is useful in long-running
conversations with an extended Session/persistence context.
For merge
if there is a persistent instance with the same identifier currently associated with the session, copy the state of the given object onto the persistent instance
if there is no persistent instance currently associated with the session, try to load it from the database, or create a new persistent instance
the persistent instance is returned
the given instance does not become associated with the session, it remains detached
persist() and merge() has nothing to do with the fact that the columns are modified or not .Use dynamic-update as #Tomasz Nurkiewicz has suggested for saving only the modified columns .Use dynamic-insert for inserting not null columns .
Some JPA providers such as EclipseLink support fetch groups. So you can load a partial instance and update it.
See,
http://wiki.eclipse.org/EclipseLink/Examples/JPA/AttributeGroup
I'm building a multi-tenant app with a shared database using .NET MVC 3 and PetaPoco.
The tenant id (along with other info) is saved in a FormsAuth cookie on login and is available to all controllers via a BaseController property. Most tables, (i.e. apart from apart the main 'Tenants' table) include a TenantId column.
Instead of manually adding a 'WHERE TenantId = X' to all CRUD on the feature tables, is there a way I can dynamically add this to the query just before its executed? In other words, maybe maintain a list of tables, and if the query is for one of those tables, then dynamically add in the TenantId filter?
The benefit of course is that it removes the need to add in the filter manually thus reducing the chances its left out. I did find an example using NHibernate, which I doubt can be repurposed. I am using Ninject in case that makes a difference.
There is an OnCommandExecuting method on the Database class which you can override in your own sub class, and modify the sql as you wish just before it gets executed. We use this feature for converting isnull/nvl between Sql Server and Oracle.
You could just leave a marker in your sql and replace it here.
I have an custom entity which needs to have a case number for an XRM Application, can I generate a case number from the Service -> Case.
If this is not possible, how can I do this with a plugin, I've looked at the crmnumbering.codeplex.com but this doesn't support 2011, anybody outthere have a solution or should I rewrite it myself?
thanks
I've ran into this same type of issue (I need a custom # for an entity). Here's how you can do it:
Create an Entity called "Counter"
Add a field called "new_customnumber", make it a string or a number depending on what you want
Create a new record for that entity with whatever you want in the new_customnumber field (let's say "10000")
Create a plugin (EntityNumberGenerator) that goes out and grabs that record (you'll probably want to set the security on this record/entity really tight so no one can mess with the numbers)
On Create of the "custom entity" fire the plugin. Grab the value in new_customnumber save it to the "custom entity" (let's say in a "case" field) increment the new_customnumber and save it to the Counter entity.
Warning, I'm not sure how this is with concurrency. Meaning I'm not sure if 2 custom entities being created at the same time can grab the same number (I haven't ran into an issue yet). I haven't figured out a way to "lock" a field I've retrieved in a plugin (I'm not sure it's possible).
You will be unable to create a custom number for custom entities from the normal area you set a case number.
Look at the CRM2011sdk\sdk\samplecode\cs\plug-ins\accountnumberplugin.cs plugin. It's really similar to what you want.
Ry
I haven't seen one for 2011 yet. Probably easiest to write it yourself.
I've always created a database with a table with a single column which is an IDENTITY column. Write an SP to insert, save the IDENTITY value to a variable, and DELETE the row all within a transaction. Return the variable. Makes for a quick and easy plug-in and this takes care of any concurrency issues.
The performance is fast and the impact to your SQL server is minimal.
I am using Sql tables without rowversion or timestamp. However, I need to use Linq to update certain values in the table. Since Linq cannot know which values to update, I am using a second DataContext to retrieve the current object from database and use both the database and the actual object as Input for the Attach method like so:
Public Sub SaveCustomer(ByVal cust As Customer)
Using dc As New AppDataContext()
If (cust.Id > 0) Then
Dim tempCust As Customer = Nothing
Using dc2 As New AppDataContext()
tempCust = dc2.Customers.Single(Function(c) c.Id = cust.Id)
End Using
dc.Customers.Attach(cust, tempCust)
Else
dc.Customers.InsertOnSubmit(cust)
End If
dc.SubmitChanges()
End Using
End Sub
While this does work, I have a problem though: I am also using StoredProcedures to update some fields of Customer at certain times. Now imagine the following workflow:
Get customer from database
Set a customer field to a new value
Use a stored procedure to update another customer field
Call SaveCustomer
What happens now, is, that the SaveCustomer method retrieves the current object from the database which does not contain the value set in code, but DOES contain the value set by the stored procedure. When attaching this with the actual object and then submit, it will update the value set in code also in the database and ... tadaaaa... set the other one to NULL, since the actual object does not contain the changed made by the stored procedure.
Was that understandable?
Is there any best practice to solve this problem?
If you make changes behind the back of the ORM, and don't use concurrency checking - then you are going to have problems. You don't show what you did in step "3", but IMO you should update the object model to reflect these changes, perhaps using OUTPUT TSQL paramaters. Or; stick to object-oriented.
Of course, doing anything without concurrency checking is a good way to lose data - so my preferred option is simply "add a rowversion". Otherwise, you could perhaps read the updated object out and merge things... somehow guessing what the right data is...
If you're going to disconnect your object from one context and use another one for the update, you need to either retain the original object, use a row version, or implement some sort of hashing routine in your database and retain the hash as part of your object. Of these, I highly recommend the Rowversion option as well. Using the current value as the original value like you are trying to do is only asking for concurrency problems.