Question

以下代码需要2分钟左右的时间才能删除3万条记录，我确信这太长了。我在这里看到的大多数类似问题都可以通过使用SQLiteTransaction对象来解决，但我已经做到了。

private void removeProxiesButton_Click(object sender, EventArgs e)
{
    using (var conn = new SQLiteConnection(Properties.Settings.Default.dbConnectionString))
    {
        conn.Open();

        using (var trans = conn.BeginTransaction())
        {
            using (var cmd = new SQLiteCommand("DELETE FROM Proxy WHERE IP=@ip AND Port=@port", conn, trans))
            {
                foreach (DataGridViewRow row in proxiesDataGridView.SelectedRows)
                {
                    var proxy = proxies[row.Index];
                    cmd.Parameters.AddWithValue("@ip", proxy.IP);
                    cmd.Parameters.AddWithValue("@port", proxy.Port);
                    cmd.ExecuteNonQuery();
                    proxies.Remove(proxy);
                }
            }

            trans.Commit();
        }
    }
}

这是CREATE表的Proxy语句。

CREATE TABLE "Proxy" 
(
     `ProxyID` INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE, 
     `Status` TEXT, 
     `IP` TEXT, 
     `Port` INTEGER, 
     `Country` TEXT, 
     `Speed` INTEGER, 
     `DateAdded` TEXT 
)

Answer 1

使用StringBuilder构建一个长的SQLite语句，并且仅执行一次SQLiteCommand对象会大大加快工作速度。

private void removeProxiesButton_Click(object sender, EventArgs e)
{
    using (var conn = new SQLiteConnection(Properties.Settings.Default.dbConnectionString))
    {
        conn.Open();
        var sb = new StringBuilder();
        sb.Append("DELETE FROM Proxy WHERE ProxyID IN (");

        foreach (DataGridViewRow row in proxiesDataGridView.SelectedRows)
        {
            var proxy = proxies[row.Index];
            sb.Append(proxy.ProxyID + ",");
        }
        sb[sb.Length - 1] = ')';
        using (var cmd = new SQLiteCommand(sb.ToString(), conn))
        {
            cmd.ExecuteNonQuery();
        }
    }
}

即使使用事务，C＃SQLite Bulk参数化DELETE还是很慢？

1 个答案: