I want separate environments on a single MongoDB database.
How can I prefix my collections dynamically?
For example, something with an option on MongoClient:
client = pymongo.MongoClient(MONGO_URI, prefix="devenv1")
db = client[DB_NAME]
db.users.find() # -> would transparently run db.devenv1_users.find()
db.users.find()
is synonymous with
db['users'].find()
and also:
collection = 'users'
db[collection].find()
So now you can control the collection name through a variable and set it to whatever prefix you like.
Related
I have:
class MyUser(Model):
today_ref_viewed_ips = ManyToManyField(
UniqAddress,
related_name='today_viewed_users',
verbose_name="Adresses visited referal link today")
...
On some croned daily request I do:
for u in MyUser.objects.all():
u.today_ref_viewed_ips.clear()
Can it be done on DB server with update?
MyUser.objects.all().update(...)
Ok, I can't update, thanks. But only thing I need is to TRUNCATE m2m internal table, is it possible to perform from django? How to know it's name whithout mysql's console "SHOW TABLES"?
If you want to update the m2m fields only and do not want to delete the m2m objects you can use the following:
#if you have **list of pk** for new m2m objects
today_ref_pk = [1,2,3]
u = MyUser.objects.get(pk=1)
u.today_ref_viewed_ips.clear()
u.today_ref_viewed_ips.add(*today_ref_pk)
for django >=1.11 documentation:
# if you have the **list of objects** for new m2m and you dont have the
# issue of race condition, you can do the following:
today_ref_objs = [obj1, obj2, obj3]
u = MyUser.objects.get(pk=1)
u.today_ref_viewed_ips.set(today_ref_objs, clear=True)
Query-1:
No, you cannot use .update() method to update a ManyToManyField.
Django's .update() method does not support ManyToManyField.
As per the docs from the section on updating multiple objects at once:
You can only set non-relation fields and ForeignKey fields using this
method. To update a non-relation field, provide the new value as a
constant. To update ForeignKey fields, set the new value to be the new
model instance you want to point to.
Query-2:
If you want to delete all the objects of m2m table, you can use .delete() queryset method.
MyModel.objects.all().delete() # deletes all the objects
Another method is to execute the raw SQL directly. This method is faster than the previous one.
from django.db import connection
cursor = connection.cursor()
cursor.execute("TRUNCATE TABLE table_name")
Query-3:
To get the table name of a model, you can use db_table model Meta option.
my_model_object._meta.db_table # gives the db table name
For my current project I need to load a dataset and different ontologies and expose everything as linked data using Fuseki with TDB and Pubby. Pubby will take a data set from a single location and create URIs based on that location, therefore if we need multiple different locations (as in the case with 2–3 separate ontologies), that would be easy to do with Pubby by adding another data set.
The concept of dataset seems to also apply to Fuseki.
Essentially I will need to expose three types of URIs:
www.mywebsite.com/project/data
www.mywebsite.com/project/data/structure
www.mywebsite.com/project/ontology
In order to create such URIs with Pubby 0.3.3. you will have to specify lines like these:
conf:dataset [
conf:sparqlEndpoint <sparql_endpoint_url_ONE>;
conf:sparqlDefaultGraph <sparql_default_graph_name_ONE>;
conf:datasetBase <http://mywebsite.com/project/>;
conf:datasetURIPattern "(data)/.*";
(...)
]
Each data set specified in Pubby will take its data from a certain URL (typically a SPARQL endpoint).
For ontologies you will have a dataset that uses the second a datasetURIPattern like this one:
conf:dataset [
conf:sparqlEndpoint <sparql_endpoint_url_TWO>;
conf:sparqlDefaultGraph <sparql_default_graph_name_TWO>;
conf:datasetBase <http://mywebsite.com/project/>;
conf:datasetURIPattern "(ontology)/.*";
(...)
]
As you can see the differences would be at the following: conf:sparqlEndpoint (the SPARQL endpoint), conf:sparqlDefaultGraph (the default Graph), conf:datasetURIPattern (needed for creating the actual URIs with Pubby).
It is not however clear to me how can I have separate URIs for the data sets when using Fuseki. When using Sesame, for example, I just create two different repositories and this trick works like charm when publishing data with Pubby. Not immediately clear with
The examples from the official Fuseki documentation present a single dataset (read-only or not, etc), but none of them seem to present such a scenario. There is no immediate example where there is a clear separation between the TBox and the ABox, even though this is a fundamental principle of Linked Data (see Keeping ABox and TBox Split).
As far as I understand this should be possible, but how? Also is it correct that the TBox and ABox can be reunited under a single SPARQL endpoint later by using (tdb:unionDefaultGraph true ;).
The dataset concept is not unique to Jena Fuseki; it's quite central in SPARQL. A dataset is a collection of named graphs and a default graph. The prefix of a URI has nothing to do with where triples about it are stored (whether in a named graph or in the default graph).
It sounds like you want to keep your ABox triples in one named graph and your TBox triples in another. Then, if the default graph is the union of the named graphs, you'll see the contents of both in the default graph. You can do that in Fuseki.
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.
In a webapp, I use Hibernate's #SQLDelete annotation in order to "soft-delete" entities (i.e. set a status column to a value that denotes their "deleted" status instead of actually deleting them from the table).
The entity code looks like this :
#Entity
#SQLDelete(sql="update pizza set status = 2 where id = ?")
public class Pizza { ... }
Now, my problem is that the web application doesn't use the owner of the schema to which the tables belong to connect to the DB. E.g. the schema (in Oracle) is called pizza, and the db user the webapp uses to connect is pizza_webapp. This is for security reasons. The pizza_webapp user only has select/update/delete rights, it can't modify the structure of the DB itself. I don't have any choice here, it is a policy that I can't change.
I specify the name of the schema where the tables actually are with the hibernate-default_schema parameter in hibernate config :
<property name="hibernate.default_schema">pizza</property>
This works fine for everything that goes through mapped entities, Hibernate knows how to add the schema name in front of the table name in the SQL it generates. But not for raw SQL, and the #SQLDelete contains raw SQL. This is executed 'as is' and results in a "table or view not found error".
So far we worked around the issue by adding synonyms to the pizza_webapp schema, pointing to the pizza schema. It works, but it is not fun to maintain across multiple DBs when entities are added.
So, is it possible to make #SQLDelete take the hibernate.default_schema parameter into account ?
(NB: Obviously I don't want to hard-code the schema name in the SQL either...)
Yes, it is possible:
#SQLDelete(sql="update {h-schema}pizza set status = 2 where id = ?")
I could not find any Hibernate solution to this problem. However I found a work-around based on an Oracle feature. I do this in to my session before using it :
//set the default schema at DB session level for raw SQL queries (see #SQLDelete)
HibernateUtil.currentSession().doWork(new Work() {
#Override
public void execute(Connection connection) throws SQLException {
connection.createStatement().execute("ALTER SESSION SET CURRENT_SCHEMA="+HibernateUtil.getDefaultSchema());
}
});
I works fine, but unfortunately only on Oracle (which is fine for us for now at least). Maybe there are different ways to achieve the same thing on other RDBMS as well ?
Edit: the the getDefaultSchema() method in my HibernateUtil class does this to get the default schema from Hibernate's config :
defaultSchema = config.getProperty("hibernate.default_schema");
where config is my org.hibernate.cfg.Configuration object.
I'm using NHibernate to connect to an ERP database on our DB2 server. We have a test schema and a production schema. Both schemas have the same table structure underneath. For testing, I would like to use the same mapping classes but point NHibernate to the test environment when needed and then back when in production. Please keep in mind that we have many production schemas and each production schema has an equivalent test schema.
I know that my XML mapping file has a schema property inside it, but since it's in XML, it's not like I can change it via a compiler directive or change the schema property based on a config file.
Any ideas?
Thank You.
No need to specify schema in the mappings: there's a SessionFactory-level setting called default_schema. However, you can't change it at runtime, as NHibernate pregenerates and/or caches SQL queries, including the schema part.
To get what I wanted, I had to use NHibernate.Mapping.Attributes.
[NHibernate.Mapping.Attributes.Class(0, Table = “MyTable”, Schema = MySchemaConfiguration.MySchema)]
In this way, I can create a class like MySchemaConfiguration and have a property inside of it like MySchema. I can either set the property's value via a compiler directive or get it through a configuration file. This way I only have to change the schema in one place and it will be reflected throughout all of the other mappings.
I have found following link that actually fixes the problem.
How to set database schema for namespace in nhibernate
The sample code could be
cfg.ClassMappings.Where(cm => cm.Table.Schema == "SchemaName")
.ForEach(cm => cm.Table.Schema = "AnotherSchemaName");
This should happen before you initialize your own data service class.
#Brian, I tried NHibernate.Mapping.Attributes, the attribute value you put inside should be a constant. So it could not be updated during run time. How could you have set the property's value using a parameter value in configuration file?
The code to fix HBM XML resources.
// This is how you get all the hbm resource names.
private static IList<string> GetAllHbmXmlResourceNames(Assembly assembly)
{
var result = new List<string>();
foreach (var resource in assembly.GetManifestResourceNames())
{
if (resource.EndsWith(".hbm.xml"))
{
result.Add(resource);
}
}
return result;
}
// This is how you get the stream for each resource.
Assembly.Load(assembly).GetManifestResourceStream(name)
// What you need to do next is to fix schema name in this stream
// Replacing schema name.
private Stream FixSchemaNameInStream(Stream stream)
{
StreamReader strStream = new StreamReader(stream);
string strCfg = strStream.ReadToEnd();
strCfg = strCfg.Replace(string.Format("schema=\"{0}\"" , originalSchemaName), string.Format("schema=\"{0}\"" , newSchemaName));
return new MemoryStream(Encoding.ASCII.GetBytes(strCfg));
}
Take a look at SchemaUpdate.
http://blogs.hibernatingrhinos.com/nhibernate/archive/2008/04/28/create-and-update-database-schema.aspx