Using the Neo4j.Driver (4.1.0) I am unable to connect a session to server's configured fabric database. It works fine in the Neo4j Browser. Is there a trick to setting the context to a fabric database?
This times out:
var session = driver.AsyncSession(o => o.WithDatabase("fabric"));
Actual database names work fine.
Does the c# driver not support setting the Session context to a fabric database?
I'm trying to execute something like the following:
use fabric.graph(0)
match ...
set...
I found a workaround by co-opting a sub-query as follows, but it seems that setting the session context would make more sense.
use fabric
call {
use fabric.graph(0)
match ...
set ...
return 0
}
return 0
I've not yet worked with fabric. But I have worked with clusters. You can only add nodes/edges to the one Neo4j database that has a WRITE role. To do this you need a small function to query the routing table and determine the write database. Here's the key query:
CALL dbms.cluster.routing.getRoutingTable({}) YIELD ttl, servers UNWIND servers as server with server where server.role='WRITE' RETURN server.addresses
You then address your write query to that specific database.
Related
In our app, we need to switch to read replica database and read from it for some read-only APIs.
We decided to use the around_action filter for that:
Switch DB to read_replica before the action
Yield
Switching back to master.
We decided to use establish_connection for switching, which did the job but later we noticed that it's not thread-safe i.e it causes our other threads to face "#<ActiveRecord::ConnectionNotEstablished: No connection pool with 'primary' found.>" issue. So this solution would have worked in the case of single-threaded servers.
Later we tried to create a new connection pool, as below which is thread-safe:
databases = Rails.configuration.database_configuration
resolver = ActiveRecord::ConnectionAdapters::ConnectionSpecification::Resolver.new(databases)
spec = resolver.spec(:read_replica)
pool = ActiveRecord::ConnectionAdapters::ConnectionPool.new(spec)
pool.with_connection { |conn|
execute SQL query here.
}
The only problem with the above approach is, we can only execute queries using execute method like conn.execute(sql_query) any AR ORM query we execute inside this with_connection block run on the original DB and not read_replica.
Seems like ActiveRecord do have its default connection and it's using it when we run AR ORM queries.
Not sure how can we execute the AR ORM query inside the with_connection block as User.where(id: 1..10).
Please note:
I am aware that we can do this natively in rails 6, need to skip that for now.
I am also aware of the Octopus gem, again need to skip on that.
Appreciate any help, Thanks.
I'm trying to create a query like this
User.find_each(created_at: [1.day.ago.utc, Date.now]) do |user|
but that didn't worked. Always return 0 users, but I do have users created in the 1 day timeframe. I believe I'm doing this query wrong, but the mongo mapper documentation says nothing about this.
Any ideas?
Activate the profiling with db.setProfilingLevel(2).
Rerun your code.
Get the query you sent to MongoDB in the system.profile collection.
Run this query in the mongoshell to check what's wrong.
Update your code to send the command you want.
Recently I was tasked with creating a SQL Server Job to automate the creation of a CSV file. There was existing code, which was using an assortment of #temp tables.
When I set up the job to execute using BCP calling the existing code (converted into a procedure), I kept getting errors:
SQLState = S0002, NativeError = 208
Error = [Microsoft][SQL Native Client][SQL Server]Invalid object name #xyz
As described in other post(s), to resolve the problem lots of people recommend converting all the #tempTables to #tableVariables.
However, I would like to understand WHY BCP doesn't seem to be able to use #tempTables?
When I execute the same procedure from within SSMS it works though!? Why?
I did do a quick and simple test using global temp tables within a procedure and that seemed to succeed via a job using BCP, so I am assuming it is related to the scope of the #tempTables!?
Thanks in advance for your responses/clarifications.
DTML
You are correct in guessing that it's a scope issue for the #temp tables.
BCP is spawned as a separate process, so the tables are no longer in scope for the new processes. SSMS likely uses sub-processes, so they would still have access to the #temp tables.
I am using django multiple DB router concepts, having multiple sites with different db's. Base database user will login with all other sub sites.
When i try syncdb in base site its worked properly(at any time), but trying syncdb with other sites works first time only, if we try next time on-wards it throws integiry error like below
django.db.utils.IntegrityError: (1062, "Duplicate entry
'22-add_somesame' for key 'content_type_id'")
Once i removed multiple DB router settings in that project means syncdb works properly(at any time).
So is this relates to multiple db router? or what else?
Please anyone advise on this, thanks.
The problem here is with the db router and django system objects. I've experienced the same issue with multiple DBs and routers. As I remember the problem here is with the auth.permission content types, which get mixed in between databases. The syncdb script otherwise tries to create these in all databases, and theb it creates permission content type for some object, which id is already reserved for a local model.
I have the following
BASE_DB_TYPES = (
'auth.user',
'auth.group',
'auth.permission',
'sessions.session',
)
and then in the db router:
def db_for_read(self, model, **hints):
if hasattr(model, '_meta') and str(model._meta) in BASE_DB_TYPES:
return 'base_db' # the alias of base db that will store users
return None # the default database, or some custom mapping
EDIT:
Also, the exception might say that you're declaring a permission 'add_somesame' for your model 'somesame', while Django automatically creates add_, delete_, edit_ permissions for all objects.
I am using rails application, my rails applications logs are should be stroed in mongoDB.
I am logging each and every controller's method call and its params its date of call etc.
Here is my code in my application controller, to log the information
db = Mongo::ReplSetConnection.new([MONGODB_PROP['host'],MONGODB_PROP['port']],:refresh_mode => :sync).db(MONGODB_PROP['database'])
au = db.authenticate(MONGODB_PROP['username'],MONGODB_PROP['password'])
if au
coll = db.collection("log_info")
doc = { :tab_name => "#{params[:controller}",:date =>"#{Time.now}"}
coll.insert(doc)
end
Obviously, my code has need some standard issues. From my implementation each time the method called happend the mongoDB connection is established .So automatically connection object is increased & it will become performance issue. i want the Single DB connection whenever it requires i need to get the connection object and perform the insert operation. How can i do this.
Please help me on this.
The easiest way is to use Mongoid and create a LogInfo class. Let mongoid handle your database connections, and you simply call:
LogInfo.create(:tab_name => "#{params[:controller}",:date =>"#{Time.now}")