Jasonnn Comments - Answer Overflow

Jasonnn

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CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

I’ll look for the documentation of SqliteConnection

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

it doesn’t crash.

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

The reason why I thought sqlite was handling it well was that when each thread uses its own connection object,

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

Like the error looks like a GC problem

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

SQLite only sees « one user » right?

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

Because if I only have one connection object

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

Umm I’m not sure, isn’t it a c# problem

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

But then I need to have some sort of « locking » mechanism?

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

Or I have one connection object that all threads use

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

Which I thought was bad

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

Well it was either I spawn one connection per thread

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

Ah I see Edit: but it says « By default, Lazy<T> objects are thread-safe. That is, if the constructor does not specify the kind of thread safety, the Lazy<T> objects it creates are thread-safe. In multi-threaded scenarios, the first thread to access the Value property of a thread-safe Lazy<T> object initializes it for all subsequent accesses on all threads, and all threads share the same data. » in the documentation

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

Thread 10 read 17 rows.
Thread 6 read 17 rows.
Thread 16 read 17 rows.
Thread 10 read 17 rows.
Thread 11 read 17 rows.
Thread 6 read 17 rows.
Thread 12 read 17 rows.
Thread 9 read 17 rows.
Thread 14 read 17 rows.
Thread 15 read 17 rows.
Thread 18 read 17 rows.
Thread 16 read 17 rows.
Thread 7 read 17 rows.
Thread 8 read 17 rows.
Thread 13 read 17 rows.
Thread 18 read 17 rows.
Thread 17 read 17 rows.
Thread 20 read 17 rows.
Thread 19 read 17 rows.
Thread 12 read 17 rows.
Thread 14 read 17 rows.
Thread 11 read 17 rows.
Thread 10 read 17 rows.
Thread 6 read 17 rows.
Thread 9 read 17 rows.
Thread 15 read 17 rows.
Thread 16 read 17 rows.
Thread 8 read 17 rows.
Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.Data.Sqlite.SqliteConnection.RemoveCommand(SqliteCommand command)
   at Microsoft.Data.Sqlite.SqliteCommand.Dispose(Boolean disposing)
   at System.ComponentModel.Component.Dispose()
   at SQLiteMultithreadingExample.SqlDatabase.QueryDatabase() in

Thread 10 read 17 rows.
Thread 6 read 17 rows.
Thread 16 read 17 rows.
Thread 10 read 17 rows.
Thread 11 read 17 rows.
Thread 6 read 17 rows.
Thread 12 read 17 rows.
Thread 9 read 17 rows.
Thread 14 read 17 rows.
Thread 15 read 17 rows.
Thread 18 read 17 rows.
Thread 16 read 17 rows.
Thread 7 read 17 rows.
Thread 8 read 17 rows.
Thread 13 read 17 rows.
Thread 18 read 17 rows.
Thread 17 read 17 rows.
Thread 20 read 17 rows.
Thread 19 read 17 rows.
Thread 12 read 17 rows.
Thread 14 read 17 rows.
Thread 11 read 17 rows.
Thread 10 read 17 rows.
Thread 6 read 17 rows.
Thread 9 read 17 rows.
Thread 15 read 17 rows.
Thread 16 read 17 rows.
Thread 8 read 17 rows.
Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
   at Microsoft.Data.Sqlite.SqliteConnection.RemoveCommand(SqliteCommand command)
   at Microsoft.Data.Sqlite.SqliteCommand.Dispose(Boolean disposing)
   at System.ComponentModel.Component.Dispose()
   at SQLiteMultithreadingExample.SqlDatabase.QueryDatabase() in

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

for some reason (I would assume the query is too fast in my MRE, but since I'm able to reproduce the problem I have that's good enough for me)

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

It’s only using around 15 threads

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

So I'm a bit confused as to what I should be doing, what's good practice, and why I have an error in the first place

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

If I do:

var connection = new SqliteConnection("Data Source=Core.db;Mode=ReadOnly");

var connection = new SqliteConnection("Data Source=Core.db;Mode=ReadOnly");

as a local variable in public static void QueryDatabase() then I don't have any problems anymore (but then I'm opening 100 different connections!) Which is why I'm pretty much convinced the problem comes from the fact that all my threads are using the same object.

25 replies

CC#

•Created by Jasonnn on 11/12/2024 in #help

Threading and Microsoft.Data.Sqlite

Here is a Minimal Reproducible Example:

using System;
using System.Data;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Data.Sqlite;

namespace SQLiteMultithreadingExample
{
    static class SqlDatabase
    {
        private static readonly Lazy<SqliteConnection> LazyConnection = new Lazy<SqliteConnection>(
            () =>
            {
                var connection = new SqliteConnection("Data Source=Core.db;Mode=ReadOnly");
                connection.Open();
                return connection;
            }
        );

        private static SqliteConnection Connection => LazyConnection.Value;
        
        public static void QueryDatabase()
        {
            using (var command = Connection.CreateCommand())
            {
                command.CommandText = "SELECT * FROM KITS";
                
                using (var reader = command.ExecuteReader())
                {
                    int rowCount = 0;

                    while (reader.Read())
                    {
                        rowCount++;
                    }

                    Console.WriteLine($"Row count in KITS table is {rowCount}");
                }
            }
        }
    }
    
    class Program
    {

        static async Task Main(string[] args)
        {
            // Number of threads/tasks
            int numberOfThreads = 100;
            Task[] tasks = new Task[numberOfThreads];

            // Start each task to open the database and query KITS table
            for (int i = 0; i < numberOfThreads; i++)
            {
                tasks[i] = Task.Run(() => SqlDatabase.QueryDatabase());
            }

            // Wait for all tasks to complete
            await Task.WhenAll(tasks);

            Console.WriteLine("All threads have completed their work.");
        }
    }
}

using System;
using System.Data;
using System.Threading;
using System.Threading.Tasks;
using Microsoft.Data.Sqlite;

namespace SQLiteMultithreadingExample
{
    static class SqlDatabase
    {
        private static readonly Lazy<SqliteConnection> LazyConnection = new Lazy<SqliteConnection>(
            () =>
            {
                var connection = new SqliteConnection("Data Source=Core.db;Mode=ReadOnly");
                connection.Open();
                return connection;
            }
        );

        private static SqliteConnection Connection => LazyConnection.Value;
        
        public static void QueryDatabase()
        {
            using (var command = Connection.CreateCommand())
            {
                command.CommandText = "SELECT * FROM KITS";
                
                using (var reader = command.ExecuteReader())
                {
                    int rowCount = 0;

                    while (reader.Read())
                    {
                        rowCount++;
                    }

                    Console.WriteLine($"Row count in KITS table is {rowCount}");
                }
            }
        }
    }
    
    class Program
    {

        static async Task Main(string[] args)
        {
            // Number of threads/tasks
            int numberOfThreads = 100;
            Task[] tasks = new Task[numberOfThreads];

            // Start each task to open the database and query KITS table
            for (int i = 0; i < numberOfThreads; i++)
            {
                tasks[i] = Task.Run(() => SqlDatabase.QueryDatabase());
            }

            // Wait for all tasks to complete
            await Task.WhenAll(tasks);

            Console.WriteLine("All threads have completed their work.");
        }
    }
}

25 replies

CC#

•Created by Jasonnn on 9/9/2024 in #help

✅ Nullable<int> and xUnit

thanks for confirming!

9 replies

CC#

•Created by Jasonnn on 9/9/2024 in #help

✅ Nullable<int> and xUnit

Ok so I definitely got scared because my IDE took time to refresh the warnings

9 replies

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