微软建议的ASP性能优化28条守则(1)
)
End Function
'' Periodically update the cached data
Sub UpdateEmploymentStatusList
Dim d, strLastUpdate
strLastUpdate = Application(?LastUpdate?)
If (strLastUpdate = ??) Or _
(UPDATE_INTERVAL < DateDiff(?s?, strLastUpdate, Now)) Then
'' Note: two or more calls might get in here. This is okay and will simply
'' result in a few unnecessary fetches (there is a workaround for this)
'' FetchEmploymentStatusList function (not shown)
'' fetches data from DB, returns an Array
d = FetchEmploymentStatusList()
'' Update the Application object. Use Application.Lock()
'' to ensure consistent data
Application.Lock
Application(?EmploymentStatusList?) = Events
Application(?LastUpdate?) = CStr(Now)
Application.Unlock
End If
End Sub
End Function
'' Periodically update the cached data
Sub UpdateEmploymentStatusList
Dim d, strLastUpdate
strLastUpdate = Application(?LastUpdate?)
If (strLastUpdate = ??) Or _
(UPDATE_INTERVAL < DateDiff(?s?, strLastUpdate, Now)) Then
'' Note: two or more calls might get in here. This is okay and will simply
'' result in a few unnecessary fetches (there is a workaround for this)
'' FetchEmploymentStatusList function (not shown)
'' fetches data from DB, returns an Array
d = FetchEmploymentStatusList()
'' Update the Application object. Use Application.Lock()
'' to ensure consistent data
Application.Lock
Application(?EmploymentStatusList?) = Events
Application(?LastUpdate?) = CStr(Now)
Application.Unlock
End If
End Sub
请参见 World''s Fastest ListBox with Application Data，上面还有一个例子。
要知道在 Session 或 Application 对象中缓存大的数组不是一个好的做法。在访问数组的任何元素之前，脚本语言的语法要求必须临时复制整个数组。例如，如果将由字符串组成的有 100,000 个元素的数组（该数组将美国邮政编码映射到当地的气象站）缓存在 Application 对象中，ASP 必须先将所有的 100,000 个气象站复制到临时数组中，然后才能提取一个字符串。在这种情况下，用自定义方法建立一个自定义组件来存储气象站 - 或使用一个词典组件会更好。
再警告大家一下，不要将婴儿与洗澡水一起倒掉：数组能快速查寻和存储在内存中是邻近的关键数据对。索引一个词典比索引一个数组要慢得多。应针对您的实际情况，选择提供最佳性能的数据结构。