下载过程中的事件

下面的伪代码概述了调用下载事件以及调用同名脚本的序列。

这些事件在MobiLink 事件概述中提供的完整事件模型中的下载位置发生。

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prepare_for_download
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modify_last_download_timestamp
fetch the next download timestamp from consolidated
prepare_for_download
if( modify_last_download_timestamp script is defined
    or prepare_for_download script is defined ) {
    COMMIT
}

------------------------------------------------------
download
------------------------------------------------------

begin_download // Connection event.
for each table being synchronized {
   begin_download // Table event.
}
   handle_DownloadData
   for each table being synchronized {
     begin_download_deletes
     for each row in download_delete_cursor {
       if( all primary key columns are NULL ) {
         send TRUNCATE to remote
       } else {
         send DELETE to remote
       }
     }
     end_download_deletes
     begin_download_rows
     for each row in download_cursor {
       send INSERT ON EXISTING UPDATE to remote
     }
     end_download_rows
   }
   modify_next_last_download_timestamp
   for each table being synchronized {
     if( begin_download table script is called ) {
        end_download // Table event
     }
}
if( begin_download connect script is called ) {
   end_download // Connection event
}
   for each table being synchronized {
     download_statistics   // Table event.
   }
     download_statistics   // Connection event.

COMMIT

注意

如果希望得到确认，并且没有从客户端获得下载确认，则整个下载事务将在统一数据库中回退。

有关 SQL Anywhere 远程数据库的信息，请参见SendDownloadACK (sa) 扩展选项。有关 UltraLite 远程数据库的信息，请参见发送下载确认同步参数。
下载流不区分插入操作与更新操作。与 download_cursor 事件关联的脚本是一个 SELECT 语句，该语句定义要下载的行。客户端将检测行是否存在，然后执行适当的插入或更新操作。
下载过程结束时，客户端将自动删除破坏参照完整性的行。

请参见参照完整性与同步。