I have Migrator.net implemented in my project and I am removing a table from the current schema. My Up() simply contains Database.RemoveTable("FooTable"). But now I'm at a bit of a loss as to what I'm supposed to do for my Down(). Do I need to manually parse all past migrations for modifications on FooTable? Is there a way to run all previous migrations on FooTable in Down()?
What about the data? If there were 50,000 rows, recreating an empty table doesn't rollback to the previous state.
To enable database downgrades with data you need to:
In Up(), detach the table from your data model (e.g. drop FKs) and rename it to something like DeleteMe_FooTable. Do not actually drop it however.
In Down(), reattach it to your data model - rename it to its original name and restore FKs.
A few days/weeks after the deployment, when you know you are 100% guaranteed never to rollback, a DBA can manually delete the table.
The idea of Down() is that it would reverse the effects of you Up() method, so technically if you ran Up() and then Down() right after your database schema would be back where you started.
in your case you would have to recreate the Table in your Down()
Related
I have got a web service which is looking for the last create table
[name_YYYYMMddHHmmss]
I have a persister job that creates and loads a table (insert or bulk)
Is there something that hides a table until it is fully loaded ?
First, I have created a technical table, it works but I will need one by keyspace (using cassandraAuth). I don’t like this.
I was thinking about tags, but it doesn’t seem to exist.
- create a table with tag and modify or remove it when the table is loaded.
There is also the table comment option.
Any ideas?
Table comment is a good option. We use it for some service information about the table, e.g. table versions tracking.
I want to store information in some activities that are modified versions of activities imported from an existing database (ecoinvent).
I know we can add fields to activities created from scratch (example). (I guess this is because the structure of the database has not yet been defined...) but is there a way of adding it to activities of an already defined database without breaking it?
The way around I found is to add entries to the author dict, which I can easily access later on. e.g.
act['author']['scenario']='myscenario'
but I admit it is not a very elegant solution.
You can just add whatever data you want. Brightway is a (semi-)schemaless database for exactly this reason.
act['foo'] = 'bar'
act.save()
I re-created my database on one of my dev environment and now when I run the migration via sequelize db:migrate, it tries to run the migrations from the first.
I don't want to re-sync/re-create the database since running migrations on the dev environment ensures that the migrations are correctly written.
Is there a way to force-mark some migrations as 'done'?
Sequelize-cli stores the migration data on a table called SequelizeMeta.
You can copy the migration filename from your existing DB and insert into the above mentioned table in new environment's DB.
All the migrations recorded would be considered as they have already ran.
Though this would stop selected migrations from running, it's not the best approach to be taken.
This metadata could also be stored in a json, though I am not very aware of the structure for it.
You can dig through the docs here
The actual way of doing is as follow,
There are two tables sequelizemeta and SequelizeMeta(Hidden)
And for skip or say migration already ran is enter value in both table like
INSERT INTO sequelizemeta (name) VALUES
('20181019072815-roles.js'),
('20181019093229-users.js')
INSERT INTO SequelizeMeta (name) VALUES
('20181019072815-roles.js'),
('20181019093229-users.js')
Note- SequelizeMeta is hidden table but we can query it.
SELECT * from seerportal.SequelizeMeta
With Entity Framework it is possible to enable migrations and create migration steps. But is there an intermediate way where it is possible to change the models, and take care of database schema changes yourself? I don't want to drop the database, because there are future production schenario's.
Now - without enable migrations - I use a code first, and when I create another property in a DbSet - lets assume for example in table 'ExistingTable' int NewField {get; set;}
And when in SQL I update my schema with
Alter table ExistingTable add column NewField int not null
the database knows existence of the new field, the Entity Framework / C# knows the property, but when running, there is some hidden check that still want's to drop my database because of the model change.
Question: can I overwrite a certain setting, in such a way that intial 'Code First' can be transformed to database first?
Removing the __MigrationHistory table from the database (Azure) did work fine for me. I made my (simple) database changes myself and published the code. It all runs fine. There is an alternative see EF Code First Migrations Deployment to an Azure Cloud Service. For a simple one-way patch (and no change history needed) removing the __MigrationHistory works fine.
This question covncerns my lack of understanding of how to use the core data undo manager and how to restore a NSManagedObject to its state before editing was done.
I am just learning my way around Core Data. I have my NSManagedObject classes set up with their dynamic accessors. I perform a fetch that returns several NSManagedObject entity results. Content from each of these entity results (first name, last name) get put into a table view, and then the user picks one out of the table for detailed view and then editing.
The detail view controller receives a pointer to the selected NSManagedObject entity. As the user edits the fields, the corresponding property value in the NSManagedObject entity is updated. This seemed like the cleanest way to manage these changes.
Now, rather than committing the changes using save, I want to provide a cancel-editing feature that rolls back to what is in the data base for that entity. I really only want to restore the one entity and not perform the entire refetch.
I tried rollback and I tried NSUndoManager (with beginUndoGrouping and endUndoGrouping), and that is not working. I don't think I understand what rollback is really supposed to do.
But in any case, I still want to restore the property values in just that single entity (taking the lazy approach to only fetch what is needed, which is the one entity) so that my detail view controller can refill its view with the correct information. Right now it is using the NSManagedObject entity values, which contain the edited values, which were cancelled.
I suppose I could just start the edit process by creating a copy of the NSManagedObject. If the cancel-editing button is pressed, I could copy it back into the original. (I might even be able to just replace the original with the copy by moving the pointer. But since the pointer has actually been passed through several objects, I'm not sure how to manage the retain number on the copy.)
Does anyone have any other suggestions?
Thanks
Using rollback should accomplish what you want and I'm not sure what it doesn't. It is probably an implementation detail error.
You can find the specific managed object/s that were updated but not yet saved by calling the context's updatedObjects.