Question

我有一个应用程序从数据库中获取大量数据，填充程序的内部结构。问题是需要花费很多时间。由于在嵌套结构的迭代期间有多个选择查询，因此该过程非常长。现在我正在考虑用很多JOINS进行更大的查询。

在此示例中，我收集了EventDefinitions。

的集合

EventDefinitions表已加入

EventMonitorTags - 一个Tag到多个EventDefinitions
EventRecipients - 一个Recipient到多个EventDefinitions
EventReports - 一个Report到多个EventDefinitions

让我向您展示一些需要优化的代码：

public static List<DatabaseStructures.EventDefinition> GetEventDefinitionCollection(bool getReportsAndRecipients, int plcNumber, bool onlyActiveEvents)
    {
        List<DatabaseStructures.EventDefinition> eventDefinitionCollection = new List<DatabaseStructures.EventDefinition>();

        string dbQuery = "SELECT * FROM EventDefinitions ed LEFT JOIN Tags t ON ed.triggerTagId = t.tagId";


        using (MySqlConnection dbConnection = new MySqlConnection(Connection.DbConnectionString))
        {
            dbConnection.Open();

            using (MySqlCommand dbCommand = new MySqlCommand(dbQuery, dbConnection))
            {
                using (MySqlDataReader dbReader = dbCommand.ExecuteReader())
                {
                    while (dbReader.Read())
                    {
                        DatabaseStructures.EventDefinition eventDefinition = FillEventDefinition(dbReader);

                        if (eventDefinition.EventActive | !onlyActiveEvents)
                        {
                            GetEventMonitorTags(ref eventDefinition);

                            if (getReportsAndRecipients)
                            {
                                GetEventReports(ref eventDefinition);
                                GetEventRecipients(ref eventDefinition);
                            }

                            eventDefinitionCollection.Add(eventDefinition);
                        }
                    }
                }
            }
        }

        return eventDefinitionCollection;
    }

然后有一个代码来为每个EventDefinition结构获取嵌套结构：

private static void GetEventMonitorTags(ref DatabaseStructures.EventDefinition eventDefinition)
    {
        MySqlConnection dbConnection = new MySqlConnection(Connection.DbConnectionString);
        using (dbConnection)
        {
            dbConnection.Open();

            string dbQuery = "SELECT tagId FROM EventMonitorTags WHERE eventDefinitionId = " + eventDefinition.Id;
            eventDefinition.MonitorTags = new ArrayList();

            using (MySqlCommand dbCommand = new MySqlCommand(dbQuery, dbConnection))
            {
                using (MySqlDataReader dbReader = dbCommand.ExecuteReader())
                {
                    while (dbReader.Read())
                    {
                        int monitorTagId = (int)dbReader["tagId"];
                        DatabaseStructures.Tag tag = Tags.Get(monitorTagId);

                        eventDefinition.MonitorTags.Add(tag);
                    }
                }
            }
        }
    }

    private static void GetEventReports(ref DatabaseStructures.EventDefinition eventDefinition)
    {
        MySqlConnection dbConnection = new MySqlConnection(Connection.DbConnectionString);
        using (dbConnection)
        {
            dbConnection.Open();

            string dbQuery = "SELECT * FROM EventReports WHERE eventDefinitionId = " + eventDefinition.Id;
            eventDefinition.ReportDefinitions = new ArrayList();

            using (MySqlCommand dbCommand = new MySqlCommand(dbQuery, dbConnection))
            {
                using (MySqlDataReader dbReader = dbCommand.ExecuteReader())
                {
                    while (dbReader.Read())
                    {
                        int reportDefinitionId = (int)dbReader["reportDefinitionId"];
                        DatabaseStructures.ReportDefinition reportDefinition = ReportsDefinition.Get(reportDefinitionId);

                        eventDefinition.ReportDefinitions.Add(reportDefinition);
                    }
                }
            }
        }
    }

    private static void GetEventRecipients(ref DatabaseStructures.EventDefinition eventDefinition)
    {
        MySqlConnection dbConnection = new MySqlConnection(Connection.DbConnectionString);
        using (dbConnection)
        {
            dbConnection.Open();

            string dbQuery = "SELECT * FROM EventRecipients WHERE eventDefinitionId = " + eventDefinition.Id;
            eventDefinition.Recipients = new ArrayList();

            using (MySqlCommand dbCommand = new MySqlCommand(dbQuery, dbConnection))
            {
                using (MySqlDataReader dbReader = dbCommand.ExecuteReader())
                {
                    while (dbReader.Read())
                    {
                        int recipientId = (int)dbReader["recipientId"];
                        DatabaseStructures.Recipient recipient = Recipients.Get(recipientId);

                        eventDefinition.Recipients.Add(recipient);
                    }
                }
            }
        }
    }

在每种方法中，都会调用另一个方法来获取正确的对象。在这种情况下，我只展示一个：

public static DatabaseStructures.Tag Get(int tagId)
    {
        DatabaseStructures.Tag tag = new DatabaseStructures.Tag();
        string dbQuery = "SELECT * FROM Tags WHERE tagId = " + tagId;

        MySqlConnection dbConnection = new MySqlConnection(Connection.DbConnectionString);
        using (dbConnection)
        {
            dbConnection.Open();

            using (MySqlCommand dbCommand = new MySqlCommand(dbQuery, dbConnection))
            {
                using (MySqlDataReader dbReader = dbCommand.ExecuteReader())
                {
                    while (dbReader.Read())
                    {
                        tag = FillTag(dbReader);
                    }
                }
            }
        }

        return tag;
    }

在这种情况下，最佳做法是什么？

更快地获取大量数据库链接对象

0 个答案: