In this scenario, I have an existing database with three models:
Address, which has a 'AddressId', 'ParentId', 'City', 'State', etc
Person, which has a 'PersonId', 'Name', etc.
Company, which has a 'CompanyId', 'Name', etc.
Because Address can contain rows for more models than just one table, there's no foreign key; the Address column 'ParentId' would contain either a 'PersonId' or 'CompanyId'.
To generate my DbContext, I used Entity Framework Power Tools Beta 2. Due to the lack of referential integrity, the classes it generated for Person and Company do not contain a collection of addresses like they should.
How would I go about altering those classes to add in this "Addresses" property, and ensure it's mapped to the Address table correctly?
At the moment I'm doing something like this; I'd rather have the context map it if possible:
public IEnumerable<Address> Addresses
{
get
{
IEnumerable<Address> addresses = null;
using(MyDb db = new MyDb())
{
addresses = db.Addresses.Where(a => a.ParentId == this.PersonId)
}
return addresses;
}
}
Thanks!
If you can, you should add an unique id to the Address table and then store that id with the entity that it belongs to, whether it be a person, company, vendor etc.
If you can't because of the multiple address scenario, then you could create a new table AddressXRef table that stores the GUID's of the entities (vendor, person, company etc), and the GUID of the address; so every entity could have multiple address and EF will be quite happy with this setup as there will be keys all around.
(I'd also want some sort of address type indicator on the Xref table so I knew what kind of address it was, mailing, shipping, etc)
Create partial classes for both Company and Person which have that property you have created in it.
public partial class Company
{
public IEnumerable<Address> Addresses { ... }
}
Related
I would like to know what the best way is to create a custom lookup for a field in my table, my situation is as following:
I have Form A which has a datasource to Table A, a field on that datasource has a lookup method:
public void lookup(FormControl _formControl, str _filterStr)
{
changeCompany(companyInfo.DataArea)
{
super(_formControl, _filterStr);
}
}
The field has an EDT, which has an relation to a Table.
The table has multiple fields, 1 of them is field: GroupType (Enum), with 2 options: Suppliers and Customers.
Form A is showing all records, both with Suppliers and Customers, but i would like to filter on the records with only has the value Suppliers in Column C.
Based on the information above, what is the best way to create this custom lookup?
You can create Related field fixed relation between your tables
TableB = TableB.Id
Enum::Suppliers = TableB.GroupType
Or create a custom lookup
and set a range for field GroupType.
I'm making a web app using angularfire. I have a url for users at 'url.firebaseio.com/users'. I want to make another url to store chat-room type things at 'url.firebaseio.com/rooms'. When I create a new user using the $createUser() method, it stores the user's information under a unique ID created by $createUser() in the '/users' url. I want to do this with the new '/rooms' url, but I can't find a way to generate unique IDs in the same way without $createUser(). I can't use $createUser() because it requires an email address argument, and I just want to take in a name for the room and a password, all in an object under the unique ID for the room.
I can't think of any code to provide, so here's what a user looks like:
users: {
uniqueUserId: {
email: email#email.com,
name: name
}
}
And here's what I'd like a 'room' to look like:
rooms: {
uniqueRoomId: {
roomName: something
}
}
Is there a built-in way to do this? If not would it be best to generate IDs on my own?
I am writing an app using the Realm.io database that will pull data from another, server database. The server database has some tables whose primary keys are composed of more than one field. Right now I can't find a way to specify a multiple column key in realm, since the primaryKey() function only returns a String optional.
This one works:
//index
override static func primaryKey() ->String?
{
return "login"
}
But what I would need looks like this:
//index
override static func primaryKey() ->[String]?
{
return ["key_column1","key_column2"]
}
I can't find anything on the docs on how to do this.
Supplying multiple properties as the primary key isn't possible in Realm. At the moment, you can only specify one.
Could you potentially use the information in those two columns to create a single unique value that you could use instead?
It's not natively supported but there is a decent workaround. You can add another property that holds the compound key and make that property the primary key.
Check out this conversation on github for more details https://github.com/realm/realm-cocoa/issues/1192
You can do this, conceptually, by using hash method drived from two or more fields.
Let's assume that these two fields 'name' and 'lastname' are used as multiple primary keys. Here is a sample pseudo code:
StudentSchema = {
name: 'student',
primaryKey: 'pk',
properties: {
pk: 'string',
name: 'string',
lastname: 'string',
schoolno: 'int'
}
};
...
...
// Create a hash string drived from related fields. Before creating hash combine the fields in order.
myname="Uranus";
mylastname="SUN";
myschoolno=345;
hash_pk = Hash( Concat(myname, mylastname ) ); /* Hash(myname + mylastname) */
// Create a student object
realm.create('student',{pk:hash_pk,name:myname,lastname:mylastname,schoolno: myschoolno});
If ObjectId is necessary then goto Convert string to ObjectID in MongoDB
All,
I have an entity, that has several collections,- each collection is mapped lazily. When I run a criteria query, I get duplicate results for my root entity in the result set. How's that possible when all my collections are mapped lazily!
I verified, my collections, load lazily.
Here's my mapping:
Root entity 'Project':
[Bag(0, Lazy = CollectionLazy.True, Inverse = true, Cascade = "all-delete-orphan")]
[Key(1, Column = "job_id")]
[OneToMany(2, ClassType = typeof(ProjectPlan))]
public virtual IList<ProjectPlan> PlanList
{
get { return _planList; }
set { _planList = value; }
}
The criteria query is:
ICriteria criteria = session.Session.CreateCriteria<Entities.Project>()
.Add(Restrictions.Eq(Entities.Project.PROP_STATUS, !Entities.Project.STATUS_DELETED_FLAG));
.CreateAlias(Entities.Project.PROP_PLANLIST, "p")
.Add(Restrictions.Eq("p.County", 'MIDDLSEX'))
.setFirstResult(start).setMaxResults(pageSize)
.List<Entities.Project>();
I know, I can correct this problem w/ Distinct result transformer, I just want to know if this is normal behavior on lazy collections.
EDIT: I found the cause of this,- when looking at the raw SQL, the join, and where clause are correct but what baffles me is the generated Select clause,- it not only contains columns from the project entity (root entity) but also columns from the project plans entity which causes the issue I described above. I am not at work right now, but I'll try to do this: .SetProjection(Projections.RootEntity()), so I only get Project's columns in the select clause.
One way, how to solve this (I'd say so usual scenario) is: 1) not use fetching collections inside of the query and 2) use batch fetching, as a part of the mapping
So, we will always be querying the root entity. That will give us a flat result set, which can be correctly used for paging.
To get the collection data for each recieved row, and to avoid 1 + N issue (goign for collection of each record) we will use 19.1.5. Using batch fetching
The mapping would be like this
[Bag(0, Lazy = CollectionLazy.True
, Inverse = true
, Cascade = "all-delete-orphan"
, BatchSize = 25)] // Or something similar to batch-size="25"
[Key(1, Column = "job_id")]
[OneToMany(2, ClassType = typeof(ProjectPlan))]
public virtual IList<ProjectPlan> PlanList
{
...
Some other similar QA (with the almost same details)
How to Eager Load Associations without duplication in NHibernate?
NHibernate QueryOver with Fetch resulting multiple sql queries and db hits
Is this the right way to eager load child collections in NHibernate
And we still can filter over the collection items! but we have to use subqueries, an example Query on HasMany reference
In RavenDB I can store objects of type Products and Categories and they will automatically be located in different collections. This is fine.
But what if I have 2 logically completely different types of products but they use the same class? Or instead of 2 I could have a generic number of different types of products. Would it then be possible to tell Raven to split the product documents up in collections, lets say based on a string property available on the Product class?
Thankyou in advance.
EDIT:
I Have created and registered the following StoreListener that changes the collection for the documents to be stored on runtime. This results in the documents correctly being stored in different collections and thus making a nice, logically grouping of the documents.
public class DynamicCollectionDefinerStoreListener : IDocumentStoreListener
{
public bool BeforeStore(string key, object entityInstance, RavenJObject metadata)
{
var entity = entityInstance as EntityData;
if(entity == null)
throw new Exception("Cannot handle object of type " + EntityInstance.GetType());
metadata["Raven-Entity-Name"] = RavenJToken.FromObject(entity.TypeId);
return true;
}
public void AfterStore(string key, object entityInstance, RavenJObject metadata)
{
}
}
However, it seems I have to adjust my queries too in order to be able to get the objects back. My typical query of mine used to look like this:
session => session.Query<EntityData>().Where(e => e.TypeId == typeId)
With the 'typeId' being the name of the new raven collections (and the name of the entity type saved as a seperate field on the EntityData-object too).
How would I go about quering back my objects? I can't find the spot where I can define my collection at runtime prioring to executing my query.
Do I have to execute some raw lucene queries? Or can I maybe implement a query listener?
EDIT:
I found a way of storing, querying and deleting objects using dynamically defined collections, but I'm not sure this is the right way to do it:
Document store listener:
(I use the class defined above)
Method resolving index names:
private string GetIndexName(string typeId)
{
return "dynamic/" + typeId;
}
Store/Query/Delete:
// Storing
session.Store(entity);
// Query
var someResults = session.Query<EntityData>(GetIndexName(entity.TypeId)).Where(e => e.EntityId == entity.EntityId)
var someMoreResults = session.Advanced.LuceneQuery<EntityData>(GetIndexName(entityTypeId)).Where("TypeId:Colors AND Range.Basic.ColorCode:Yellow)
// Deleting
var loadedEntity = session.Query<EntityData>(GetIndexName(entity.TypeId)).Where(e =>
e.EntityId == entity.EntityId).SingleOrDefault();
if (loadedEntity != null)
{
session.Delete<EntityData>(loadedEntity);
}
I have the feeling its getting a little dirty, but is this the way to store/query/delete when specifying the collection names runtime? Or do I trap myself this way?
Stephan,
You can provide the logic for deciding on the collection name using:
store.Conventions.FindTypeTagName
This is handled statically, using the generic type.
If you want to make that decision at runtime, you can provide it using a DocumentStoreListner