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Sql.cs
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Sql.cs
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using System;
using System.Collections.Generic;
using System.Data;
using System.Diagnostics;
using System.Threading;
using MySql.Data.MySqlClient;
namespace EpidemicManager
{
public static class Sql
{
/// <exception cref="MySqlException" />
public static void Execute(string sql, params object[] args)
{
var command = CreateCommand(sql, args);
Sleep();
using var transaction = command.Connection.BeginTransaction();
try
{
command.ExecuteNonQuery();
}
catch (MySqlException)
{
transaction.Rollback();
throw;
}
transaction.Commit();
ReleaseCommand(command);
}
/// <exception cref="MySqlException" />
public static DataRowCollection Read(string sql, params object[] args)
{
var command = CreateCommand(sql, args);
Sleep();
using var reader = new MySqlDataAdapter(command);
using var table = new DataTable();
reader.Fill(table);
ReleaseCommand(command);
return table.Rows;
}
private const int MinConnections = 5;
private const int MaxConnections = 10;
private static readonly List<MySqlConnection> freeConnections;
private static readonly LinkedList<MySqlCommand> waitingCommands;
private static int connectionsCount;
static Sql()
{
freeConnections = new List<MySqlConnection>(MinConnections);
waitingCommands = new LinkedList<MySqlCommand>();
for (var i = 0; i < MinConnections; i++)
{
var connection = CreateConnection();
freeConnections.Add(connection);
}
}
[Conditional("DebugSql")]
private static void Log(string message)
{
var threadId = Thread.CurrentThread.ManagedThreadId;
Console.WriteLine(threadId + ":\t" + message);
}
private static MySqlConnection CreateConnection()
{
const string ConnectionString = "server=localhost;database=infectious_disease;uid=root;pwd=123456";
var connection = new MySqlConnection(ConnectionString);
try
{
connection.Open();
}
catch (MySqlException)
{
connection.Close();
connection.Dispose();
throw;
}
connectionsCount++;
return connection;
}
private static MySqlCommand CreateCommand(string sql, params object[] args)
{
var command = new MySqlCommand
{
CommandText = sql,
};
for (var i = 0; i < args.Length; i++)
{
var name = $"@{i}";
var value = args[i];
var parameter = new MySqlParameter(name, value);
var parameters = command.Parameters;
parameters.Add(parameter);
}
lock (freeConnections)
{
if (freeConnections.Count > 0)
{
Log("use free connection");
var index = freeConnections.Count - 1;
command.Connection = freeConnections[index];
freeConnections.RemoveAt(index);
}
else
{
if (connectionsCount < MaxConnections)
{
Log("use new connection");
command.Connection = CreateConnection();
}
else
{
Log("wait connection");
waitingCommands.AddLast(command);
}
}
}
while (command.Connection == null) ;
return command;
}
private static void ReleaseCommand(MySqlCommand command)
{
var connection = command.Connection;
command.Dispose();
lock (freeConnections)
{
if (freeConnections.Count < MinConnections)
{
if (waitingCommands.Count > 0)
{
Log("put connection to wating command.");
var waitingCommand = waitingCommands.First.Value;
waitingCommands.RemoveFirst();
waitingCommand.Connection = connection;
}
else
{
Log("put connection to free.");
freeConnections.Add(connection);
}
}
else
{
Log("release connection");
connection.Dispose();
connectionsCount--;
}
}
}
[Conditional("DebugSql")]
private static void Sleep()
{
Thread.Sleep(50);
}
}
}