I was trying dapper orm and recently they added asyncquery support. I googled it about that. It is wonderful if you have heavy traffic on your site. I was trying that with postgressql and dapper. Now, in connection if I am passing simple connection string it works fine. But as per couple of articles it is not true async if I want to use it, I need async connection string.
Now, I don't know how to use with Postgresql and npgsql. Here is complete article for reference where author explains how to do it with Sql Server.
What I need to do if I want same with Postgresql?
Please let me know if any further requirement needed.
The author of this article is somewhat wrong - in .NET 4.5 the AsynchronousProcessing property is ignored because it is no longer required. You can just start calling the Async methods of SqlClient without any special connection strings.
Whether the operations will execute asynchronously, depends on the database provider. For example, the default implementation of DbCommand.ExecuteDbDataReaderAsync actually executes synchronously and blocks the calling thread. SqlCommand overrides this method and executes asynchronously.
Unfortunately, NpgsqlCommand doesn't override this method so you are left with synchronous execution only.
Related
I am designing a set of unit and integration tests with a friend of mine, and we had a doubt. We know the answer, at least, what is more likely to be true. However, we would like to hear your thoughts.
We are designing a test for MongoDB, and we expect that we should receive a promise, after asking to save a document. So far so good.
What about if we change the database??? can we assume for sure that all databases when queried will return a promise??
I guess regarding the _id, it depends from database to database, we are using _id from MongoDB for testing reasons.
We are using the following test using in Jest
create://this method do exist on service, however, at the moment of testing, it is empty, just a placeholder
jest.fn().mockImplementation((cat: CreateCatDto) =>
Promise.resolve({ _id: 'a uuid', ...cat })
)
The idea is to design backends that do not depend on the database, but for testing and developing reasons, we are using MongoDB and PostgreSQL.
Keep in mind the term promise doesn't exist as a concept for all databases, and to provide a conclusive answer to your question for all databases is not possible.
That being said, if by promise you mean the primary key or identity (in general database terms) after inserting new data, then the answer is no, there is no guarantee, not even on PostgreSQL that'll you be able to do that. It's possible for tables, even in PostgreSQL, to exist without those constraints.
Otherwise, if by promise, you mean specifically the concept in a procedural or functional language like JavaScript (as your example code in your update indicates), then yes, you should always receive a promise object if your application code is utilizing asynchronous calls appropriately.
But that would be regardless of what the asynchronous call was to whether it's a database directly (and regardless of what database system that was), an API endpoint, or another piece of application code. Also, in that case, your question (or any follow up questions) would be better suited for StackOverflow.com.
Can I assume that all databases return a promise?
No. Most if not all database wire protocols are synchronous, meaning the client blocks until it gets a response. Even the databases that expose some sort of RESTful APIs are synchronous, because HTTP.
Some client-side drivers may wrap this synchronous logic and exhibit asynchronous behaviour by returning something like JavaScrpt Promises or Java Futures, but it is entirely up to the driver implementation you choose to use.
I am aware of CQRS pattern wherein Query to be used for Reading data and Command to be used for updating the data.
In a peculiar case where the rest api is POST but not updating the data directly rather calling an external POST api of other system and passing the details.
In such case which one holds true - use Query or Command?
*Update *
System involves multiple DB. Not necessarily different DB for query and command however
Super simple. If you know for sure the call will not update or modify state or data, then it's a query, if it does (or might) then it's a command.
However, CQRS is often more about the physical structure of your system. You might have separate command and query databases... and that complicates the answer. It can have both logical and physical aspects.
I had added the Extended event to track sql calls which is slowing down my system leading to Timeout exceptions and other
CREATE EVENT SESSION [longrunning_statements] ON SERVER
ADD EVENT sqlserver.sql_statement_completed(
WHERE ([duration]>(2000000) AND [database_id]=(9)))
ADD TARGET package0.event_file(SET filename=N'c:\capture\xe_longrunning_statement.xel',metadatafile=N'c:\capture\xe_longrunning_statement.xem')
WITH (MAX_MEMORY=4096 KB,EVENT_RETENTION_MODE=ALLOW_SINGLE_EVENT_LOSS,MAX_DISPATCH_LATENCY=30 SECONDS,MAX_EVENT_SIZE=0 KB,MEMORY_PARTITION_MODE=NONE,TRACK_CAUSALITY=OFF,STARTUP_STATE=OFF)
GO
But i noticed it does not register sql server updates/read queries/procedures calls from Entity Framework but only logged my sql queries run using SSMS.
Any ideas are appreciated
UPDATE:
I use EF6.1 which used i think batches to save data.
Instead of trying to capture sqlserver.sql_statement_completed I would capture sqlserver.sql_batch_completed and sqlserver.rpc_completed for application/API issued queries/stored procedures.
If that does not work then removing the filters(or at least the duration filter (as Andrey is suggesting in the comments) would probably give us more insight on why the queries are not being captured.
I need to regularly check the database for updated records. I currently use TimerTask which works fine. However, I've found its efficiency is not good and consumes a lot of server resouces. Is there a solution which can fulfill my requirement but is better?
def checknewmessages() = Action{
request =>
TimerTask(5000){
//code to check database
}
}
I can think of two solutions:
You can use the ReactiveMongo driver for Play which is completely non-blocking and async and capped collection in Mongo DB.
Please see this for an example -
https://github.com/sgodbillon/reactivemongo-tailablecursor-demo
How to listen for changes to a MongoDB collection?
If you are using a database that doesn't support a push mechanisms you can implement that using an Actor by scheduling messages to itself at regular intervals.
If your logic is in your database (stored procedures etc) you could simply create a cron job.
You could also create a command line script that encapsulates the logic and schedule (cron again).
If you have your logic in your web application, you could again create a cron job that simply makes an API call to your app.
I have a complex reporting application that allows clients to login and view reports for their client data. There are several sections of the application where there are database calls, using various controllers. I need to make sure that client A doesn't get client B's information via header manipulation.
The system authenticates, and assignes them a clientID and roleID. If your roleID >1, that means you work for the company hosting the data, and you can see all client info. I want to create a catch-all that basically works like this:
if($roleID > 1) {
...send query to database
}else {
if(...does this query select a record with clientID other than my $auth->clientID){
do not execute query
}else {
execute query
}
}
The problem is, I want this to run for every query that goes to the server... how can I place this code as a "roadblock" between the application and the DB? I already use Zend_Profiler to look at queries, so I know it is somehow possible, but cannot discern this from the Profiler code...
I can always write an authentication function and pass selected queries that way, but this catch-all would be easier to implement across all of the calls and would be future proof. Any help is appreciated.
it's application design fault.
you shoud use 'service architecture' - the only one entry point for queries would be a service. and any checks inside it.
If this is something you want run on every query, I'd suggest extending Zend_Db_Select and overwrite either the query() or assemble() functions to add in your logic. You'll also want to add a way for it to be aware of your $auth object.
Another option is to extend your database adapter so you can intercept the queries directly. IMO, you should try and do this at the application level though.
Depending on your database server, you can put a trace on the DB side.
Here's an example for Oracle:
http://orafaq.com/wiki/SQL_Trace