I am getting data from two tables using join and putting setIntegrityCheck(false) in my model. Now I need to call save() on that object. I know when you put setIntegrityCheck(false), you cannot call save(), delete() or update() to this object. I have seen this question, but it doesn't address the answer.
So any way around?
ZF supports only Table data gateway and row data gateway pattern. AFAIK setIntegrityCheck() will only allow you to join tables within Db_Table_Select which will help you to build SQL query. Anyway you can not hydrate custom SQL results to Db_Table_Row objects - which supports save(). You have to simply update each row separatly. For more sofisticated approach you will have to use data mapper pattern - like Doctrine.
Related
Is there a way using Entity Framework Core to get nested data without having to iterate through it? like a simple SQL select with joins i would like to show all data on the same table
Sounds like you know the SQL you need to get the data you want. So I suggest you create a database view and then map your ef entity to that. As long as you are just reading ef will treat the view just like it would any other table.
I think youre looking for .Include() and .ThenInclude() methods that allow you to load related data in a eager way.
More on that topic on the official entity framework documentation at MSDN
I am trying to profile EF to understand more of its inner workings, I have tried to add two entities using the Add method and the AddRange method, then of course committing with the SaveChanges method. And here is what I got on the profiler in both cases.
Does this mean that EF actually makes two trips to the database one per insert? which means that if I am trying to insert 100 entities for example this will mean 100 trips to the database? which will greatly impact performance. or am I missing something here?
Yes, that is correct, it will issue one database call per item attempting to be added, as it is using the standard SQL INSERT command in this case.
The alternatives would be to use BULKINSERT, such as using a stored procedure that takes in an object such as a DataTable.
I am developing a SPA using Angular-Breeze-WebAPI-EntityFramework.
Now Breeze uses the Entity Framework metadata information to create it's own Breeze models. We use this in our application for Breeze validation.
So far, it's all been nice and easy. Now we are having to create a search page (say for querying customers). The search can be by Customer.Name or by Product.Id (which would return a list of customers who have bought that product). The result is a ng-repeater, which displays Customer.Name, Order.LastPlaced etc.
if you are getting confused by the tables and columns, forget that. What I am only trying to get to is that, both the search object and the result object are not 1:1 with Entity tables (or objects). So obviously I feel the need to create a custom object (one for the search and one for the results). My question primarily is where and how do I create that object?
If I create it at the data layer, Breeze would have no idea of the metadata for each of the properties (since it uses EF for that).
I obviously can't create just a JavaScript object, since I will have to query the database (using EF) to search and populate the object.
So where does one create such a custom object (traversing multiple tables) such that Breeze still can figure out the metadata and perform validation and such when the need arises?
Thank you all.
You can create metadata on the client for types that the server either doesn't know about or doesn't have the schema for. See http://www.breezejs.com/documentation/metadata-by-hand.
We are using DTOs server side, and have configured a dbcontext using fluent api in order to give breeze the metadata it needs. We map 1:1 to our real database entities, and each DTO contains a simple subset of the real database entity properties.
This works great, but now I need to figure out a way to make queries efficient - i.e. if the Breeze client queries for a single item I don't want to have to create a whole set of DTO objects before I can filter. i.e. I want to figure out a way to execute the filter/sort on the actual entities, but still return DTO objects.
I guess I need to figure out a way to intercept the query execution in order to query my real database entities and return a DTO instead of the real database entity.
Any ideas for how to best approach this?
Turns out that if you use projection in a link statement, e.g.
From PossibleCustomer As Customer
In Customers
Select New CustomerDto With {.Id = PossibleCustomer.Id,
.Name = PossibleCustomer.Name,
.Email = PossibleCustomer.Email}
.. then linq is smart enough to still optimize any queries to the database - i.e. if I query on the linq statement above to filter for a single item by Id, the database is hit with that query for just a single item and a single DTO is created. Pretty clever stuff. This only works if you do a direct projection in the linq statement - if you call off to a function to create your DTO then this won't work.
Just in case others are facing the same scenario, you might want to look at AutoMapper - it can create these projections for you using a model you create just once - avoids all those huge linq statements that are hard to read and validate. The automapper projections (assuming you stick to the simple stuff) still allow the linq to entities magic that ensures you don't have to do table scans when you create your DTOs.
Is it possible to do any type of programmatic data transformation in Entity Framework 5 Code First migrations?
There is an Sql() method to execute queries, but it has return type void and I don't see any way to get the results of the queries I perform.
Example
I have table Recipe with one-to-many relationship to Ingredient. For various reasons I want to convert this to a Ingredients JSON string property instead. The only approach I can think of is something like this:
Create new column IngredientsJson
For each recipe, query its ingredients, construct a JSON string programmatically and insert into the new column.
Drop the old table Ingredient.
You should use db 'initializer' for what you want - and/ore 'Seed' of a sort (as to where to inject into the EF flow).
You can > take a look at this post with a customized < initializer - that performas both Db Create... and Migrate. It's not cut and paste solution, but mostly works (it was just a fast go at the problem, you'd need to adjust a bit, it has couple fixes below).
MigrateDatabaseToLatestVersion dose only the migration part - and you need seed-ing exposed - or manually wrap that part (the main point is in 'checks' done for different situations - i.e. when to 'engage' into migration - or seeding).
Migration should go first, and db 'creation' kind of doesn't make much sense, except for seeding.
You override Seed (you created) to put any db handling there - you have the DbContext exposed - and you can also call SqlQuery if needed.
How to create initializer to create and migrate mysql database?