SqlDataReader 在访问值方面的性能差异？

发布于 2024-07-12 12:01:09 字数 442 浏览 6 评论 0原文

当从 SqlDataReader 访问值时，这两者之间是否存在性能差异：

string key = reader.GetString("Key");

或者

string key = reader["Key"].ToString();

在此代码示例中：

string key;

using (SqlDataReader reader = cmd.ExecuteReader())
{
    while (reader.Read())
    {
        key = reader.GetString("Key");
        // or
        key = reader["Key"].ToString();
    }
}

原文

When accessing values from an SqlDataReader is there a performance difference between these two:

string key = reader.GetString("Key");

string key = reader["Key"].ToString();

In this code sample:

string key;

using (SqlDataReader reader = cmd.ExecuteReader())
{
    while (reader.Read())
    {
        key = reader.GetString("Key");
        // or
        key = reader["Key"].ToString();
    }
}

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幽梦紫曦～ 2024-07-19 12:01:09

我刚刚查看了.NET源代码，两种访问方法本质上是相同的。唯一的区别是第二个进行了额外的拳击。因此，第一个对应于类似的内容（在基本类型的情况下）：

int key = GetInternalSQLDataAsInt32("Key");

而第二个对应的是：

int key = (int)(object)GetInternalSQLDataAsInt32("Key");

GetInternalSQLDataAsInt32(...) 函数表示将数据从 SQL 编组到 .NET 的 SQL 数据库机制。

但如上所述，基于字符串的键和基于序数的键之间预计会有更显着的差异。

I’ve just peeked into the .NET source code, and the two access methods are essentially the same. The only difference is that the second does an additional boxing. So the first one corresponds to something like (in case of elementary types):

int key = GetInternalSQLDataAsInt32("Key");

while the second one would be:

int key = (int)(object)GetInternalSQLDataAsInt32("Key");

The GetInternalSQLDataAsInt32(...) function represents the SQL data library machinery of marshalling data from SQL to .NET.

But as pointed above, a more significant difference can be expected between string-based keys and ordinal-based keys.

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猫瑾少女 2024-07-19 12:01:09

一位 Microsoft MVP 就此撰写了一篇博客文章：
http://jeffbarnes. net/portal/blogs/jeff_barnes/archive/2006/08/09/Maximize-Performance-with-SqlDataReader.aspx

这是他的结论：

                                    .NET 1.1    .NET 2.0
Ordinal Position:                   8.47        9.33
Get Methods:                        11.36       8.07
Case Sensitive:                     14.51       12.53
Case Insensitive (All Upper):       13.93   12.23
Case Insensitive (All Lower):       14.47   12.48
Case Insensitive (Mixed):           14.48   12.57

但实际上，除非您正在处理大量的行，否则它不是不值得担心。

A Microsoft MVP wrote a blog entry about this:
http://jeffbarnes.net/portal/blogs/jeff_barnes/archive/2006/08/09/Maximize-Performance-with-SqlDataReader.aspx

Here are his conclusions:

                                    .NET 1.1    .NET 2.0
Ordinal Position:                   8.47        9.33
Get Methods:                        11.36       8.07
Case Sensitive:                     14.51       12.53
Case Insensitive (All Upper):       13.93   12.23
Case Insensitive (All Lower):       14.47   12.48
Case Insensitive (Mixed):           14.48   12.57

But really, unless you are dealing with a significant number of rows, it isn't worth worrying about.

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