I have a habit of keeping a separate Migration Class for every custom Type or Part. A lot of the time I want to attach a Taxonomy Field for the same Taxonomy to several custom Parts. Since I'm not sure which migration will run first, I have to check if the Taxonomy already exists in each migration and create it if it doesn't, leading to a lot of duplicate code. I could move my code into a service for the sake of re-usability/maintainability but it would be easier still if I knew for sure which migration was going to get executed first.
They should be running in order of dependency, starting with the dependency, ending with the module depending on it.
However, for this sort of thing, you might want to try recipes rather than migrations.
Related
I am working on a project built by some people before me, when I was creating some new tables using sqlalchemy I figured out that the method which creates tables were removed. So, I had to put it in code again to create tables. What I am wondering is if it doesn't need to stay in code after creating tables. is there any problem with keeping it there?
Here is the line code that I am talking about:
models.Base.metadata.create_all(bind=engine)
Metadata.create_all takes a checkfirst keyword argument which determines whether SQLAlchemy should check whether a table already exists before trying to create it. The default value of this argument is True, so once the tables have been created future invocations will have no effect, beyond emitting a few queries.
You can leave the code in place - it will be useful when a developer needs to create a fresh environment.
Is it possible to create a model where the relationships are dynamically generated by the application?
I saw the KeystoneJS project that does a nice job of defining the model (see: http://keystonejs.com/docs/database/#relationship-definitions)
But these need to be defined by node, I'm interested in creating these within the application. Are there any ORMs or framework projects that already do that? I I've seen frameworks like the MODxCMS that allow users to create additional fields, by putting everything from the custom (templatevar) values into one table. think mongodb would be great for setting this up without this single table approach.
Any idea how to go about setting this kind of system up? I'm not sure where to start.
I guess mongoose might help you here. And you may want to have a look at mongo-relation too.
I'm adding 4 new checkboxes to an entity and its form. There are already instances of this entity created in production. I need to have these checkboxes defaulted to checked on these existing entity instances. I set the default value of the field but apparently this only gets used when a new instance of the entity is created. Is there an easy way to set these on all the existing instances?
I could use a one-off workflow, but I don't know how many instances of this entity there are and due to auditing requirements I can't access the production environment.
You could create execute some JavaScript on the load of the form. Of course, this wouldn't update all of the values in the database, but it would update it before a user is able to view it. Do you need all the values in the database defaulted, or will java script work?
Edit
Your best options are either an update multiple ( you can increase the number of records an advanced find returns to 250 records per page) and continue to update all records manually, or perform a batch update. See this related SO question.
There's another way, too. You could write a console application that connects to your server (not that hard if you've done it before and don't have to make it general). Then, you simply execute an update on the service fetching all the existing entities and updating them after the change is made.
As #Daryl says, there's probably a way to do that from the GUI too, but real programmers do it the hard way. :)
Of course I'm kidding. I just love to type code, hehe. Never the less - once you start coding, you have full freedom to affect the data any way you need, forever.
You can do this by exporting the records and change the value for the field and then re-import back it.
I am wondering about the model-first approach. I wish to design a new database using the model designer in VS2012. The new features of the model designer such as coloring and splitting up model sections are wonderful. Hopefully there will be purpose for using the model designer beyond initially creating a new database.
I would like to perform the following steps...
using the model designer, visually design and push the model to create the initial database and a table
add data to the table
make a change to the table in the model designer (e.g. add a field)
push the changes to the database (i.e. update the database)
NOT LOSE MY DATA FROM STEP 2. Also, just to clear any confusion... did I mention that I DON'T WISH TO LOSE THE DATA?
Please, please tell me this obvious need (i.e. the need to evolve the the tables and their fields without losing data, starting from scratch) has not been overlooked in iteration FIVE of EF.
This page on EF (http://msdn.microsoft.com/en-us/data/ee712907.aspx) makes things sound that the developer has equal choices between coding first and modeling first. To me, the intro video on the page creates a similar impression.
It would be nice if there were a simple menu option or better yet just a way to establish "automatic pushes to DB" upon changes to the model. That way whenever changes are made and the SAVE button is clicked, a dialog could appear "Update database?".
I see that using code-first there is a migrations option. I cannot seem to find the same for model-first. And I don't understand why this wouldn't be possible... after all the code that I would have written in code-first does indeed exist - it was created by the model-first code generation.
I'm keeping my fingers crossed in hopes someone will have a simple solution, perhaps something I've just overlooked and all this rambling/venting is in vain. :-)
You really have to use code-first if you want to modify your database when the model changes. Even then it's not some magical automated process but you'll have to script the changes.
With model first your best option is to generate a new database each time and create a change script (DDL) by using a tool like Redgate's SQL Compare or a Visual Studio Sql Server Database Project.
I'd like to add that it is virtually impossible to synchronize a database automatically with a model. Some changes require manual intervention, e.g. removing a field and adding another field cannot be distinguished from renaming/retyping a field. Some changed can easily be done in a model, but would require a table rebuild script in Sql Server (e.g. changing field order), or a combination of modified content and structure (e.g. making a field not null, adding a foreign key).
At the moment the only thing to do is:
Copy your database file... (backup)
Allow EF to recreate the database according to model
Per table copy-paste your records from backup to your new db.
This is not that easy as you need to copy paste in a specific order because of relations and it will only be good for minor changes such as adding columns and new tables or removing scalar columns or removing tables.
But I am certain that this is the begining of a correct approach to deal with the problem which later on can be automated by writing a more generic migration app between two databases which share same table names and relations.
Deeper problems begin when the relations are not the same / table names changed / column names changed.
I have certain objects in my domain which are not aggregate roots/entities, yet I still need to retrieve them from a database. I don't want to confuse things by creating repositories for these things. So, what are alternative data access patterns? Would you simply create a DAO for them, while still of course separating the interface?
Edit:
Some more detail on what I'm doing. I need to create a code. This code has certain rules as to its format. One of the rules is that the final character must be a unique number incremented by one from the last code generated. For example:
ABCD1
ABCD2
ABCD3
So, I'm keeping a table with one row, one column to store the number in question. Now, I don't want to consider this number an entity and create a repository for it - that's overkill. I just need a way of retrieving the number, adding 1 to it, and saving it. I know there are myriad ways I could do it, but I'm wondering if there's an customary way.
There are several data access patterns that could apply, in theory. You'd need to provide more detail though if you want us to suggest a specific pattern.
Without more detail, all I can suggest is to consider looking into Martin Fowler's Patterns of Enterprise Application Architecture book.
Edit: Customary way? No, not that I can think of - it really depends on where and how you're using this unique code in your domain. If I were doing this, I'd probably create a small service that speaks directly to the database to perform this function - not as heavy-weight as a repository, and very focused on the problem at hand.
Based on the edit: I would look first at the context in which you need to create that code. Perhaps there are some related entities or something that you are missing.
btw, I find the question really interesting as it comes up from time to time while coding specific features. I usually end up finding I was missing something on the scenario and it ends up fitting well with the normal repository pattern.
After surveying the options I'm going with the Table Gateway pattern.