In EF 6 we used database initializers for the following reasons:
Seeding data
Using seeding to define indices
Using seeding to define the database collation
Using seeindg to set "sparse"
Deciding on the action if the database model does not match (e.g., drop-and-recreate or create-if-not-exists)
Seeding and indices can now be defined in OnModelCreating, however, I still need a hook to execute raw SQL commands to define the database collation and set "sparse" - how to do that in EF Core?
What decides in EF Core which "initialization strategy" (e.g., drop-and-recreate) is performed when connection to the database? There does not seem to be a replacement for this at all?
Related
In one of my projects, I am using an existing SQL Server database. All the database scripts are managed using DBUp and SQL script migrations.
In my application, I am using Entity Framework Core to communicate with this database. When I configure my entities in EF configurations, should I still define functions like IsRequired(), HasMaxLenth() etc.?
I am not using these EF configurations to generate migration scripts; all the migration is outside of EF. I am just using these configurations to communicate with the database.
When I configure my Entities in EF configurations, should I still define functions like IsRequired(), HasMaxLenth() etc.?
Other than table and column name mapping and data type mapping, it's not required, but additional model metadata might be used by front-end components for validation.
In general, yes, you should keep them. Many of these configurations are used throughout EF to make decisions at runtime. For example, some queries can be further optimized if EF knows that a column is never NULL, the max length is used to configure the SQL parameters it sends to the database, and unique constraints are used to sort SQL statements during SaveChanges.
While a few things like constraint names, non-unique indexes, index filters, and sequences aren't currently used at runtime, it's hard to know which ones EF will and won't use, so it's best just to keep them all.
And sometimes, database features like always encrypted on SQL Server, will fail entirely if the mappings aren't precise.
When defining a index manually in SQL Server (via CREATE INDEX statement) and not specifying this index in the EFCore DBContext (we're using v2.2 and the Fluent API), will the index be considered anyway or what effect does specifying the index in EF Core have when generating SQL queries etc.? I'm not really sure what the real effect is from a technical point of view.
Thanks in advance
Indexes in general are just part of the physical database (store) model and do no affect the runtime behavior of EF Core (except of course the PK, but it is special anyway and unique index/constraint is assumed regardless of whether it actually exists). The primary (and only) case for having index related fluent API/data annotations currently is to be able to generate physical database schema with migrations.
It's partially mentioned in the Indexes part of the Performance topic of the official EF Core documentation:
As a general rule, there isn't any special EF knowledge to using indexes or diagnosing performance issues related to them; general database knowledge related to indexes is just as relevant to EF applications as to applications not using EF.
Our team is thinking of utilizing Entity Framework Core code-first to help model the database. We can have both DB projects and EF models, as per article here Database Projects vs. Entity Framework Database Migrations utilizing schema compares, just trying to figure out what will be the source of truth?
Does Entity Framework support all features in SQL Server SSDT Database Projects?
What features does EF Core 2 not support? (eg, does it not support any of following: triggers, views, functions, stored procedures, encryption keys, certificates, db properties (ansi null, quoted identifier), partitions)
I am trying to locate the Microsoft Resource.
tl;dr Database Projects are feature-rich, but database-first. Migrations is code-first, but has a very limited built-in set of database features.
For many people it won't be relevant to compare Database Projects and Migrations. They represent two different modes of working with Entity Framework. Migrations is code-first, DP is database-first. Sure, you can use migrations to control the database schema and besides that keep a DP in sync with the generated database to satisfy DBAs (as the link suggests). But both lead their own separate lives and there's no Single Source Of Truth.
So comparing them is useful if you're not sure yet wich working mode you're going to choose.
For me the most important difference is that DP will cover all database objects and detect all changes between them when comparing databases. Migrations only detect changes between a database and the mapped model. And the set of options for generating database objects is very limited. For everything you need additionally you have to inject SQL statements into the migration code. These statements are your own responsibility. You have to figure out yourself if a migration needs an ALTER PROCEDURE statement or not (for example). EF won't complain if the script and the database differ in this respect.
This is the main reason why I've never been a great fan of migrations. It's virtually impossible to maintain a mature database schema including storage, file groups, privileges, collations, and what have you.
Another advantage of DP is that they're great in combination with source control. Each database object has its own file and it's very easy to check the change history of each individual object. That's not possible with generated migrations. Indeed, many intermediate changes may never make it to a generated migration.
Of course the obvious advantage of migrations is the possibility to do a runtime check (albeit incomplete) whether the code and the database match. In database-first projects you need to create your own mechanism for that.
EF Core is only ORM.
1) You should be ready to create all DB objects except tables manually. What I create manually: constrates (defaults as well as conditions). Since this is code first - there is no need in SP, functions and so on. If you use ORM - DB is only storage. Of course practice is important. For me default constraints adds comfort on tables where I create test data manually. And conditions also are usefull in situations when you do not trust your (team) code.
2) you will do creation (and dropping) of views, triggers, sp and so on to the "migration" code (there is such concept in EF) in plain sql:
migrationBuilder.Sql("CREATE VIEW ...");
As a result you could have a separate "migration" program (e.g. command line tool) that install or remove both Ef Core tables and your manually created objects, do and revert the data migrations.
"EF Core migrations" is quite complex api (reserve a week for learning). Interesting topics: managing several dbcontexts in one db, createing db object during migration from model annotations, unistall. Or find a freelancer for it (this part of project is good for outsourcing).
I don't want to give my sql user the permissions to create databases.
Is there any way to create the database manually and then have entity framework create the tables inside it?
I'm certain EF Core is smart enough to handle this case. Just create the database, set your permissions and run the command dotnet ef update-database (assuming you have a valid migration).
Usually, an application (or multiple applications) use the same database from separate DbContext classes, which handle their own bounded context (a logical piece of the whole). That would require being able to recognize that Databases and Tables have already been created, and issue appropriate add and alter commands to the schema.
At my client site the database user has permissions to execute stored procedures only.
Database user doesn’t have permissions to execute queries directly.
But I have used Entity Framework, and no stored procedures used.
What can I do?
In such scenario it is better to use native SQL + ADO.NET directly. The main power of EF is in mapping, linq / ESQL querying and loading strategies. Once you are limited to stored procedures you will lose support for latter two = no querying and no loading strategies. You will still have support for mapping but it will come with performance costs and it will demand strict limitations on your stored procedures.
The Entity Framework allows you to map each entity to a set of stored procedures that will execute the insert, delete and update.
That way the user won't have to execute queries directly when modifying the data in your database.
If the user also doesn't have Select permissions, you need stored procedures to access the data. The Entity Framework can help you because you can import Stored Procedures in the SSDL part of your EDMX and then you can map those stored procedures to functions on your ObjectContext.