C#、SQlite：opening/closing 次后无法打开 SQLite 数据库文件

Question

public long getCntFriend()
{
    long numOfFriend = 0;
    // Construct SQL connection
    SqliteConnectionStringBuilder connBuilder = new SqliteConnectionStringBuilder();
    connBuilder.DataSource = this.dbPath;
    connBuilder.Version = 3;
    connBuilder.JournalMode = SQLiteJournalModeEnum.Delete;
    SqliteConnection connection = new SqliteConnection(connBuilder.ToString());
    SqliteCommand cmd = new SqliteCommand(connection);

    try 
    {
        connection.Open();
        cmd.CommandText = "SELECT COUNT(*) FROM user, follow WHERE target = " + egoID + " AND source = id " +
        " AND isProtected = 0 AND followingsCount < " + followingsCountConstraint +
        " AND followersCount < " + followerCountConstraint +
        " AND tweetsCount >= " + tweetCountConstraint;
        numOfFriend = (long)cmd.ExecuteScalar();
        cmd.Dispose ();
    }
    catch (SqliteException sqlError)
    {
        Console.WriteLine(sqlError.Message);
        Environment.Exit (-1);
    }
    finally 
    {
        connection.Close();
        connection.Dispose();
        cmd.Dispose();
        connection = null;
        cmd = null;
    }

    return numOfFriend;
}

你好

我的 C# 项目需要重复访问许多 SQLite 数据库文件。我已确保遵循 'try'、'catch' 和 'finally' 程序并正确关闭 Sqlite 数据库连接。

我遇到的一个问题是，在我的 C# 项目 opens/closes 数据库文件大约 120 次 之后，SQLite 给出了 "Unable to open database file" 的错误。（请见附件截图文件）

我的环境：Mac、Xamarin Studio、C#、Mono.Sqlite

我应该怎么做才能解决这个问题？

提前致谢。

Answer 1

好的，我在 Xamarin 的 iOS 项目中使用 Sqlite.net 库。

我创建了一个名为 'sqlite-test.db3' 的快速而肮脏的 sqlite 数据库和一个名为 'users' 的 table 并添加了 3 个用户和一些代码来测试，也许它有帮助，也许没有，但我让函数在 for 循环中执行 120 次没有问题。

我在主代码中的测试循环是

int friendCount = 0;

for(int x = 0; x < 120; x++){
    friendCount = getCntFriend ();

    Console.WriteLine (@"friendCount after opening database " + x + " times: " + friendCount);
}

我的 getCntFriend 方法版本和获取连接的辅助函数

public SQLite.SQLiteConnection GetConnection ()
    {
        var sqliteFilename = "/Users/my_user_name_on_imac_machine/dev_projects/OpenSqlLiteTest/OpenSqlLiteTest/sqlite-test.db3";
        var conn = new SQLite.SQLiteConnection(sqliteFilename);
        // Return the database connection
        return conn;
    }

    public int getCntFriend()
    {
        int numOfFriend = 0;
        SQLite.SQLiteConnection sqliteConn = null;
        SQLite.SQLiteCommand sqliteCommand = null;

        // Construct SQL connection

        try{
            sqliteConn = GetConnection ();
        }catch(Exception ex){
            Console.WriteLine ("SqliteConnection exception: " + ex.Message);
        }

        if(sqliteConn != null){
            using(sqliteConn){
                sqliteCommand = new SQLite.SQLiteCommand (sqliteConn);
                sqliteCommand.CommandText = "SELECT count(*) FROM 'users';";

                try{
                    numOfFriend = sqliteCommand.ExecuteScalar<int>();
                }catch(Exception exCmd){
                    Console.WriteLine ("Exception on Command execution: " + exCmd.Message);
                }
            }   
        }

        return numOfFriend;
    }

我在调试器中的测试输出

2015-12-01 12:44:46.087 OpenSqlLiteTest[11149:474199] friendCount after opening database 0 times: 3
2015-12-01 12:44:46.088 OpenSqlLiteTest[11149:474199] friendCount after opening database 1 times: 3
2015-12-01 12:44:46.088 OpenSqlLiteTest[11149:474199] friendCount after opening database 2 times: 3
2015-12-01 12:44:46.089 OpenSqlLiteTest[11149:474199] friendCount after opening database 3 times: 3
2015-12-01 12:44:46.089 OpenSqlLiteTest[11149:474199] friendCount after opening database 4 times: 3
2015-12-01 12:44:46.089 OpenSqlLiteTest[11149:474199] friendCount after opening database 5 times: 3
2015-12-01 12:44:46.090 OpenSqlLiteTest[11149:474199] friendCount after opening database 6 times: 3
2015-12-01 12:44:46.090 OpenSqlLiteTest[11149:474199] friendCount after opening database 7 times: 3
2015-12-01 12:44:46.090 OpenSqlLiteTest[11149:474199] friendCount after opening database 8 times: 3
2015-12-01 12:44:46.091 OpenSqlLiteTest[11149:474199] friendCount after opening database 9 times: 3
2015-12-01 12:44:46.091 OpenSqlLiteTest[11149:474199] friendCount after opening database 10 times: 3
2015-12-01 12:44:46.091 OpenSqlLiteTest[11149:474199] friendCount after opening database 11 times: 3
2015-12-01 12:44:46.092 OpenSqlLiteTest[11149:474199] friendCount after opening database 12 times: 3
2015-12-01 12:44:46.092 OpenSqlLiteTest[11149:474199] friendCount after opening database 13 times: 3
2015-12-01 12:44:46.092 OpenSqlLiteTest[11149:474199] friendCount after opening database 14 times: 3
2015-12-01 12:44:46.093 OpenSqlLiteTest[11149:474199] friendCount after opening database 15 times: 3
2015-12-01 12:44:46.093 OpenSqlLiteTest[11149:474199] friendCount after opening database 16 times: 3
2015-12-01 12:44:46.093 OpenSqlLiteTest[11149:474199] friendCount after opening database 17 times: 3
2015-12-01 12:44:46.094 OpenSqlLiteTest[11149:474199] friendCount after opening database 18 times: 3
2015-12-01 12:44:46.094 OpenSqlLiteTest[11149:474199] friendCount after opening database 19 times: 3
2015-12-01 12:44:46.095 OpenSqlLiteTest[11149:474199] friendCount after opening database 20 times: 3
2015-12-01 12:44:46.095 OpenSqlLiteTest[11149:474199] friendCount after opening database 21 times: 3
2015-12-01 12:44:46.095 OpenSqlLiteTest[11149:474199] friendCount after opening database 22 times: 3
2015-12-01 12:44:46.096 OpenSqlLiteTest[11149:474199] friendCount after opening database 23 times: 3
2015-12-01 12:44:46.096 OpenSqlLiteTest[11149:474199] friendCount after opening database 24 times: 3
2015-12-01 12:44:46.096 OpenSqlLiteTest[11149:474199] friendCount after opening database 25 times: 3
2015-12-01 12:44:46.096 OpenSqlLiteTest[11149:474199] friendCount after opening database 26 times: 3
2015-12-01 12:44:46.097 OpenSqlLiteTest[11149:474199] friendCount after opening database 27 times: 3
2015-12-01 12:44:46.097 OpenSqlLiteTest[11149:474199] friendCount after opening database 28 times: 3
2015-12-01 12:44:46.097 OpenSqlLiteTest[11149:474199] friendCount after opening database 29 times: 3
2015-12-01 12:44:46.098 OpenSqlLiteTest[11149:474199] friendCount after opening database 30 times: 3
2015-12-01 12:44:46.098 OpenSqlLiteTest[11149:474199] friendCount after opening database 31 times: 3
2015-12-01 12:44:46.098 OpenSqlLiteTest[11149:474199] friendCount after opening database 32 times: 3
2015-12-01 12:44:46.099 OpenSqlLiteTest[11149:474199] friendCount after opening database 33 times: 3
2015-12-01 12:44:46.099 OpenSqlLiteTest[11149:474199] friendCount after opening database 34 times: 3
2015-12-01 12:44:46.100 OpenSqlLiteTest[11149:474199] friendCount after opening database 35 times: 3
2015-12-01 12:44:46.100 OpenSqlLiteTest[11149:474199] friendCount after opening database 36 times: 3
2015-12-01 12:44:46.101 OpenSqlLiteTest[11149:474199] friendCount after opening database 37 times: 3
2015-12-01 12:44:46.101 OpenSqlLiteTest[11149:474199] friendCount after opening database 38 times: 3
2015-12-01 12:44:46.102 OpenSqlLiteTest[11149:474199] friendCount after opening database 39 times: 3
2015-12-01 12:44:46.102 OpenSqlLiteTest[11149:474199] friendCount after opening database 40 times: 3
2015-12-01 12:44:46.102 OpenSqlLiteTest[11149:474199] friendCount after opening database 41 times: 3
2015-12-01 12:44:46.103 OpenSqlLiteTest[11149:474199] friendCount after opening database 42 times: 3
2015-12-01 12:44:46.103 OpenSqlLiteTest[11149:474199] friendCount after opening database 43 times: 3
2015-12-01 12:44:46.103 OpenSqlLiteTest[11149:474199] friendCount after opening database 44 times: 3
2015-12-01 12:44:46.104 OpenSqlLiteTest[11149:474199] friendCount after opening database 45 times: 3
2015-12-01 12:44:46.104 OpenSqlLiteTest[11149:474199] friendCount after opening database 46 times: 3
2015-12-01 12:44:46.104 OpenSqlLiteTest[11149:474199] friendCount after opening database 47 times: 3
2015-12-01 12:44:46.104 OpenSqlLiteTest[11149:474199] friendCount after opening database 48 times: 3
2015-12-01 12:44:46.105 OpenSqlLiteTest[11149:474199] friendCount after opening database 49 times: 3
2015-12-01 12:44:46.105 OpenSqlLiteTest[11149:474199] friendCount after opening database 50 times: 3
2015-12-01 12:44:46.105 OpenSqlLiteTest[11149:474199] friendCount after opening database 51 times: 3
2015-12-01 12:44:46.106 OpenSqlLiteTest[11149:474199] friendCount after opening database 52 times: 3
2015-12-01 12:44:46.106 OpenSqlLiteTest[11149:474199] friendCount after opening database 53 times: 3
2015-12-01 12:44:46.106 OpenSqlLiteTest[11149:474199] friendCount after opening database 54 times: 3
2015-12-01 12:44:46.106 OpenSqlLiteTest[11149:474199] friendCount after opening database 55 times: 3
2015-12-01 12:44:46.107 OpenSqlLiteTest[11149:474199] friendCount after opening database 56 times: 3
2015-12-01 12:44:46.107 OpenSqlLiteTest[11149:474199] friendCount after opening database 57 times: 3
2015-12-01 12:44:46.107 OpenSqlLiteTest[11149:474199] friendCount after opening database 58 times: 3
2015-12-01 12:44:46.108 OpenSqlLiteTest[11149:474199] friendCount after opening database 59 times: 3
2015-12-01 12:44:46.108 OpenSqlLiteTest[11149:474199] friendCount after opening database 60 times: 3
2015-12-01 12:44:46.108 OpenSqlLiteTest[11149:474199] friendCount after opening database 61 times: 3
2015-12-01 12:44:46.108 OpenSqlLiteTest[11149:474199] friendCount after opening database 62 times: 3
2015-12-01 12:44:46.109 OpenSqlLiteTest[11149:474199] friendCount after opening database 63 times: 3
2015-12-01 12:44:46.109 OpenSqlLiteTest[11149:474199] friendCount after opening database 64 times: 3
2015-12-01 12:44:46.109 OpenSqlLiteTest[11149:474199] friendCount after opening database 65 times: 3
2015-12-01 12:44:46.109 OpenSqlLiteTest[11149:474199] friendCount after opening database 66 times: 3
2015-12-01 12:44:46.110 OpenSqlLiteTest[11149:474199] friendCount after opening database 67 times: 3
2015-12-01 12:44:46.110 OpenSqlLiteTest[11149:474199] friendCount after opening database 68 times: 3
2015-12-01 12:44:46.110 OpenSqlLiteTest[11149:474199] friendCount after opening database 69 times: 3
2015-12-01 12:44:46.111 OpenSqlLiteTest[11149:474199] friendCount after opening database 70 times: 3
2015-12-01 12:44:46.111 OpenSqlLiteTest[11149:474199] friendCount after opening database 71 times: 3
2015-12-01 12:44:46.111 OpenSqlLiteTest[11149:474199] friendCount after opening database 72 times: 3
2015-12-01 12:44:46.111 OpenSqlLiteTest[11149:474199] friendCount after opening database 73 times: 3
2015-12-01 12:44:46.112 OpenSqlLiteTest[11149:474199] friendCount after opening database 74 times: 3
2015-12-01 12:44:46.112 OpenSqlLiteTest[11149:474199] friendCount after opening database 75 times: 3
2015-12-01 12:44:46.112 OpenSqlLiteTest[11149:474199] friendCount after opening database 76 times: 3
2015-12-01 12:44:46.113 OpenSqlLiteTest[11149:474199] friendCount after opening database 77 times: 3
2015-12-01 12:44:46.113 OpenSqlLiteTest[11149:474199] friendCount after opening database 78 times: 3
2015-12-01 12:44:46.113 OpenSqlLiteTest[11149:474199] friendCount after opening database 79 times: 3
2015-12-01 12:44:46.113 OpenSqlLiteTest[11149:474199] friendCount after opening database 80 times: 3
2015-12-01 12:44:46.114 OpenSqlLiteTest[11149:474199] friendCount after opening database 81 times: 3
2015-12-01 12:44:46.114 OpenSqlLiteTest[11149:474199] friendCount after opening database 82 times: 3
2015-12-01 12:44:46.114 OpenSqlLiteTest[11149:474199] friendCount after opening database 83 times: 3
2015-12-01 12:44:46.114 OpenSqlLiteTest[11149:474199] friendCount after opening database 84 times: 3
2015-12-01 12:44:46.115 OpenSqlLiteTest[11149:474199] friendCount after opening database 85 times: 3
2015-12-01 12:44:46.115 OpenSqlLiteTest[11149:474199] friendCount after opening database 86 times: 3
2015-12-01 12:44:46.115 OpenSqlLiteTest[11149:474199] friendCount after opening database 87 times: 3
2015-12-01 12:44:46.116 OpenSqlLiteTest[11149:474199] friendCount after opening database 88 times: 3
2015-12-01 12:44:46.116 OpenSqlLiteTest[11149:474199] friendCount after opening database 89 times: 3
2015-12-01 12:44:46.116 OpenSqlLiteTest[11149:474199] friendCount after opening database 90 times: 3
2015-12-01 12:44:46.116 OpenSqlLiteTest[11149:474199] friendCount after opening database 91 times: 3
2015-12-01 12:44:46.117 OpenSqlLiteTest[11149:474199] friendCount after opening database 92 times: 3
2015-12-01 12:44:46.117 OpenSqlLiteTest[11149:474199] friendCount after opening database 93 times: 3
2015-12-01 12:44:46.117 OpenSqlLiteTest[11149:474199] friendCount after opening database 94 times: 3
2015-12-01 12:44:46.118 OpenSqlLiteTest[11149:474199] friendCount after opening database 95 times: 3
2015-12-01 12:44:46.118 OpenSqlLiteTest[11149:474199] friendCount after opening database 96 times: 3
2015-12-01 12:44:46.118 OpenSqlLiteTest[11149:474199] friendCount after opening database 97 times: 3
2015-12-01 12:44:46.118 OpenSqlLiteTest[11149:474199] friendCount after opening database 98 times: 3
2015-12-01 12:44:46.119 OpenSqlLiteTest[11149:474199] friendCount after opening database 99 times: 3
2015-12-01 12:44:46.119 OpenSqlLiteTest[11149:474199] friendCount after opening database 100 times: 3
2015-12-01 12:44:46.119 OpenSqlLiteTest[11149:474199] friendCount after opening database 101 times: 3
2015-12-01 12:44:46.120 OpenSqlLiteTest[11149:474199] friendCount after opening database 102 times: 3
2015-12-01 12:44:46.120 OpenSqlLiteTest[11149:474199] friendCount after opening database 103 times: 3
2015-12-01 12:44:46.120 OpenSqlLiteTest[11149:474199] friendCount after opening database 104 times: 3
2015-12-01 12:44:46.120 OpenSqlLiteTest[11149:474199] friendCount after opening database 105 times: 3
2015-12-01 12:44:46.121 OpenSqlLiteTest[11149:474199] friendCount after opening database 106 times: 3
2015-12-01 12:44:46.121 OpenSqlLiteTest[11149:474199] friendCount after opening database 107 times: 3
2015-12-01 12:44:46.121 OpenSqlLiteTest[11149:474199] friendCount after opening database 108 times: 3
2015-12-01 12:44:46.122 OpenSqlLiteTest[11149:474199] friendCount after opening database 109 times: 3
2015-12-01 12:44:46.122 OpenSqlLiteTest[11149:474199] friendCount after opening database 110 times: 3
2015-12-01 12:44:46.122 OpenSqlLiteTest[11149:474199] friendCount after opening database 111 times: 3
2015-12-01 12:44:46.122 OpenSqlLiteTest[11149:474199] friendCount after opening database 112 times: 3
2015-12-01 12:44:46.123 OpenSqlLiteTest[11149:474199] friendCount after opening database 113 times: 3
2015-12-01 12:44:46.123 OpenSqlLiteTest[11149:474199] friendCount after opening database 114 times: 3
2015-12-01 12:44:46.123 OpenSqlLiteTest[11149:474199] friendCount after opening database 115 times: 3
2015-12-01 12:44:46.124 OpenSqlLiteTest[11149:474199] friendCount after opening database 116 times: 3
2015-12-01 12:44:46.124 OpenSqlLiteTest[11149:474199] friendCount after opening database 117 times: 3
2015-12-01 12:44:46.124 OpenSqlLiteTest[11149:474199] friendCount after opening database 118 times: 3
2015-12-01 12:44:46.124 OpenSqlLiteTest[11149:474199] friendCount after opening database 119 times: 3

C#、SQlite：opening/closing 次后无法打开 SQLite 数据库文件

C#, SQlite: Unable to open SQLite database files after opening/closing them many times

c#

sqlite

mono

xamarin