I need to do some actions on all collections. I list them with some simple code like that:
for collection_name in db.list_collection_names():
# do something that work only on collection that are not a view
I get all collections including the views. Which is not working with what I want. So:
How can I check a collection is a view?
How can I filter out the views when getting the list of collections?
You can use list_collections() and filter out items that are not collections. Creating a view adds a system.views collection, the example below filters that out too.
from pymongo import MongoClient
db = MongoClient()['mydatabase']
for collection_name in db.list_collections(filter={'type': 'collection', 'name': {'$ne': 'system.views'}}):
print(collection_name)
Related
I need to call a collection consisting of objects that have an un-empty array in the items (array) field, I filter collection like this:
filter:
conditions:[
{
property: "items",
operator: "notEmpty",
value:null
}]
but this solution doesn't work, 500 error is returned, how to implement it?
CUBA Platform REST API doesn't support filtration by collections (#OneToMany and #ManyToMany relations).
To implement such functionality you need to create and expose predefined JPQL query on back end.
There is similar discussion on CUBA Platform forum.
I have 2 tables, evenements and participants, represented by 2 models Evenement and Participant.
Those entities are belongsToMany related, so I have a third table evenement_participant following Laravel's naming conventions, and inside are foreign evenement_id and participant_id columns.
I'm able to retrieve the relationship and I can
dd($evenement->participants)
which gives me a collection of participants.
In my controller, I have this db call:
$evenements = Evenement::withCount(['participants' => function($query) {
$query->where('is_active', 1);
}])
This withCount generates a participants_count attribute for each evenement.
In my blade view, there is a for-each loop on the evenements collection, and somewhere I do this:
$evenement->participants_count
and I face this error:
Property [participants_count] does not exist on this collection
instance.
However, if instead I do the following in the same blade view
#dd($evenement->participants_count)
it dumps me the count.
I dropped all the evenements to keep just one for testing, and I still have the same error.
Sorry, made a typo in a condition inside my blade loop
I have a document in RavenDB that looks looks like:
{
"ItemId": 1,
"Title": "Villa
}
With the following metadata:
Raven-Clr-Type: MyNamespace.Item, MyNamespace
Raven-Entity-Name: Doelkaarten
So I serialized with a type MyNamespace.Item, but gave it my own Raven-Entity-Name, so it get its own collection.
In my code I define an index:
public class DoelkaartenIndex : AbstractIndexCreationTask<Item>
{
public DoelkaartenIndex()
{
// MetadataFor(doc)["Raven-Entity-Name"].ToString() == "Doelkaarten"
Map = items => from item in items
where MetadataFor(item)["Raven-Entity-Name"].ToString() == "Doelkaarten"
select new {Id = item.ItemId, Name = item.Title};
}
}
In the Index it is translated in the "Maps" field to:
docs.Items
.Where(item => item["#metadata"]["Raven-Entity-Name"].ToString() == "Doelkaarten")
.Select(item => new {Id = item.ItemId, Name = item.Title})
A query on the index never gives results.
If the Maps field is manually changed to the code below it works...
from doc in docs
where doc["#metadata"]["Raven-Entity-Name"] == "Doelkaarten"
select new { Id = doc.ItemId, Name=doc.Title };
How is it possible to define in code the index that gives the required result?
RavenDB used: RavenHQ, Build #961
UPDATE:
What I'm doing is the following: I want to use SharePoint as a CMS, and use RavenDB as a ready-only replication of the SharePoint list data. I created a tool to sync from SharePoint lists to RavenDB. I have a generic type Item that I create from a SharePoint list item and that I serialize into RavenDB. So all my docs are of type Item. But they come from different lists with different properties, so I want to be able to differentiate. You propose to differentiate on an additional property, this would perfectly work. But then I will see all list items from all lists in one big Items collection... What would you think to be the best approach to this problem? Or just live with it? I want to use the indexes to create projections from all data in an Item to the actual data that I need.
You can't easily change the name of a collection this way. The server-side will use the Raven-Entity-Name metadata, but the client side will determine the collection name via the conventions registered with the document store. The default convention being to use the type name of the entity.
You can provide your own custom convention by assigning a new function to DocumentStore.Conventions.FindTypeTagName - but it would probably be cumbersome to do that for every entity. You could create a custom attribute to apply to your entities and then write the function to look for and understand that attribute.
Really the simplest way is just to call your entity Doelkaarten instead of Item.
Regarding why the change in indexing works - it's not because of the switch in linq syntax. It's because you said from doc in docs instead of from doc in docs.Items. You probably could have done from doc in docs.Doelkaartens instead of using the where clause. They are equivalent. See this page in the docs for further examples.
Lets say I have a model, Foo, which is big and has lots of components. For a given Ajax query I'm only interested in one particular attribute, bar, which is a column in the foos table.
Is there a simple way I could load just that attribute, and not bother with retrieving the rest of the record? For instance if all I want to know is the bar for Foo with id#__, how could I retrieve that?
You can return only specific columns by calling the select method with a string containing the attributes you want to return. For your example:
Foo.select('bar').first #<Foo bar: 1>
Keep in mind that these objects will act like normal ActiveRecord objects but return nil for any field you did not select, so take care using this functionality.
You can call select on the class name itself or any Relation, so you can chain together the ActiveRecord calls you usually use like where, etc.
I prefer this
User.where(:id => user_id).pluck(:user_name).first #'tom'
Foo.where(:age => 23).pluck(:user_name) #['tom', 'jerry', ...]
Foo.where(<condition>).select('fieldname')
Example
results = Foo.where('is_active = ?', true).select('bar')
Access the selected fields as:
results.map {|res| res.bar} returns an array of bar's
pluck(*column_names)
doc: http://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-pluck
e.g. Foo.pluck(:bar)
pick(*column_names) select just one top row's columns, docs
Similar to pluck but fetch only one row
NHibernate allows me to query a database and get an IList of objects in return. Suppose I get a list of a couple of dozen objects and modify a half-dozen or so. Does NHibernate have a way to persist changes to the collection, or do I have to persist each object as I change it?
Here's an example. Suppose I run the following code:
var hql = "from Project";
var query = session.CreateQuery(hql);
var myProjectList = query.List<Project>();
I will get back an IList that contains all projects. Now suppose I execute the following code:
var myNewProject = new Project("My New Project");
myProjectList .Add(myNewProject);
And let's say I do this several times, adding several new projects to the list. Now I'm ready to persist the changes to the collection.
I'd like to persist the changes by simply passing myProjectList to the current ISession for updating. But ISession.SaveOrUpdate() appears to take only individual objects, not collections like myProjectList. Is there a way that I can persist changes to myProjectList, or do I have to persist each new object as I create it? Thanks for your help.
David Veeneman
Foresight Systems
If you load objects like in your example - then yes you have to persist them one by one.
However, if you make a small design change, and load something like : Account that has an IList<Project> - if you specify cascade "what_cascade_you_need" in the mapping , then when you change the projects on Account , you only have to save Account and everything will get saved.