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ChenHuajunChenHuajun
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Merge pull request #199 from zuyue/master
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‎postgresql/doc/src/sgml/bgworker.sgml

Lines changed: 16 additions & 38 deletions
Original file line numberDiff line numberDiff line change
@@ -79,9 +79,8 @@ typedef struct BackgroundWorker
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int bgw_flags;
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BgWorkerStartTime bgw_start_time;
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int bgw_restart_time; /* in seconds, or BGW_NEVER_RESTART */
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bgworker_main_type bgw_main;
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char bgw_library_name[BGW_MAXLEN]; /* only if bgw_main is NULL */
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char bgw_function_name[BGW_MAXLEN]; /* only if bgw_main is NULL */
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char bgw_library_name[BGW_MAXLEN];
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char bgw_function_name[BGW_MAXLEN];
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Datum bgw_main_arg;
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char bgw_extra[BGW_EXTRALEN];
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int bgw_notify_pid;
@@ -98,9 +97,8 @@ typedef struct BackgroundWorker
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int bgw_flags;
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BgWorkerStartTime bgw_start_time;
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int bgw_restart_time; /* in seconds, or BGW_NEVER_RESTART */
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bgworker_main_type bgw_main;
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char bgw_library_name[BGW_MAXLEN]; /* only if bgw_main is NULL */
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char bgw_function_name[BGW_MAXLEN]; /* only if bgw_main is NULL */
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char bgw_library_name[BGW_MAXLEN];
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char bgw_function_name[BGW_MAXLEN];
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Datum bgw_main_arg;
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char bgw_extra[BGW_EXTRALEN];
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int bgw_notify_pid;
@@ -218,37 +216,20 @@ ____________________________________________________________________________-->
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<structfield>bgw_restart_time</structfield>是在崩溃情况下<command>postgres</command>启动进程之前等待的时间间隔，以秒计。它可以是任何正值，或者<literal>BGW_NEVER_RESTART</literal>，表示在出现崩溃后不重启进程。
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</para>
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<!--==========================orignal english content==========================
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<para>
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<structfield>bgw_main</structfield> is a pointer to the function to run when
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the process is started. This field can only safely be used to launch
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functions within the core server, because shared libraries may be loaded
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at different starting addresses in different backend processes. This will
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happen on all platforms when the library is loaded using any mechanism
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other than <xref linkend="guc-shared-preload-libraries">. Even when that
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mechanism is used, address space layout variations will still occur on
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Windows, and when <literal>EXEC_BACKEND</> is used. Therefore, most users
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of this API should set this field to NULL. If it is non-NULL, it takes
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precedence over <structfield>bgw_library_name</> and
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<structfield>bgw_function_name</>.
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</para>
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____________________________________________________________________________-->
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<para>
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<structfield>bgw_main</structfield>是进程被启动后要运行的函数指针。这个域只有在核心服务器中被用来执行函数时才是安全的，因为共享库在不同的后端进程中可能被载入到不同的起始地址。当使用除<xref linkend="guc-shared-preload-libraries">之外的任何机制载入共享库时，这种情况会在所有的平台上发生。即便是使用<xref linkend="guc-shared-preload-libraries">机制，在 Windows 上使用了<literal>EXEC_BACKEND</>的情况下，地址空间布局变化也仍然会发生。因此，这个 API 的大部分使用者应该把这个域设置为 NULL。如果这个域为非 NULL，它会优先于<structfield>bgw_library_name</>和<structfield>bgw_function_name</>。
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</para>
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<!--==========================orignal english content==========================
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<para>
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<structfield>bgw_library_name</structfield> is the name of a library in
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which the initial entry point for the background worker should be sought.
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The named library will be dynamically loaded by the worker process and
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<structfield>bgw_function_name</structfield> will be used to identify the
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function to be called. If loading a function from the core code,
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<structfield>bgw_main</> should be set instead.
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function to be called. If loading a function from the core code, this must
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be set to "postgres".
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</para>
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____________________________________________________________________________-->
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<para>
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<structfield>bgw_library_name</structfield>是应该在其中定位后台工作者初始入口点的库名称。所指的库将被工作者进程动态载入并且<structfield>bgw_function_name</structfield>将被用来标识要调用的函数。如果从核心代码载入一个函数，应该设置<structfield>bgw_main</>。
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<structfield>bgw_library_name</structfield>是应该在其中定位后台工作者初始入口点的库名称。
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所指的库将被工作者进程动态载入并且<structfield>bgw_function_name</structfield>将被用来标识要调用的函数。
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如果从核心代码载入一个函数，则必须设置为"postgres"。
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</para>
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<!--==========================orignal english content==========================
@@ -265,20 +246,17 @@ ____________________________________________________________________________-->
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<!--==========================orignal english content==========================
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<para>
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<structfield>bgw_main_arg</structfield> is the <type>Datum</> argument
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to the background worker main function. Regardless of whether that
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function is specified via <structfield>bgw_main</> or via the combination
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of <function>bgw_library_name</> and <function>bgw_function_name</>,
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this main function should take a single argument of type <type>Datum</>
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and return <type>void</>. <structfield>bgw_main_arg</structfield> will be
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passed as the argument. In addition, the global variable
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<literal>MyBgworkerEntry</literal>
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to the background worker main function. This main function should take a
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single argument of type <type>Datum</> and return <type>void</>.
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<structfield>bgw_main_arg</structfield> will be passed as the argument.
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In addition, the global variable <literal>MyBgworkerEntry</literal>
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points to a copy of the <structname>BackgroundWorker</structname> structure
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passed at registration time; the worker may find it helpful to examine
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this structure.
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</para>
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____________________________________________________________________________-->
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<para>
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<structfield>bgw_main_arg</structfield>是后台工作者主函数的<type>Datum</>参数。不管是通过<structfield>bgw_main</>还是通过<function>bgw_library_name</>和<function>bgw_function_name</>的组合指定这个函数，这个主函数应该有一个单一的<type>Datum</>类型的参数，并且返回<type>void</>。<structfield>bgw_main_arg</structfield>将被作为参数传递。此外，全局变量<literal>MyBgworkerEntry</literal>指向注册时传入的<structname>BackgroundWorker</structname>结构的一份拷贝，工作者会发现检查这个结构会很有用。
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<structfield>bgw_main_arg</structfield>是后台工作者主函数的<type>Datum</>参数。这个主函数应该有一个单一的<type>Datum</>类型的参数，并且返回<type>void</>。<structfield>bgw_main_arg</structfield>将被作为参数传递。此外，全局变量<literal>MyBgworkerEntry</literal>指向注册时传入的<structname>BackgroundWorker</structname>结构的一份拷贝，工作者会发现检查这个结构会很有用。
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</para>
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<!--==========================orignal english content==========================
@@ -348,15 +326,15 @@ ____________________________________________________________________________-->
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<!--==========================orignal english content==========================
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<para>
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Signals are initially blocked when control reaches the
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<structfield>bgw_main</> function, and must be unblocked by it; this is to
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background worker's main function, and must be unblocked by it; this is to
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allow the process to customize its signal handlers, if necessary.
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Signals can be unblocked in the new process by calling
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<function>BackgroundWorkerUnblockSignals</> and blocked by calling
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<function>BackgroundWorkerBlockSignals</>.
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</para>
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____________________________________________________________________________-->
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<para>
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当控制到达<structfield>bgw_main</>函数时，信号初始会被阻塞，并且必须被它解除阻塞。这是为了允许进程自定义它的信号处理器。在新进程中可以通过调用<function>BackgroundWorkerUnblockSignals</>来解除对信号的阻塞，还可以通过调用<function>BackgroundWorkerBlockSignals</>来阻塞信号。
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当控制到达后台进程的主函数时，信号初始会被阻塞，并且必须被它解除阻塞。这是为了允许进程自定义它的信号处理器。在新进程中可以通过调用<function>BackgroundWorkerUnblockSignals</>来解除对信号的阻塞，还可以通过调用<function>BackgroundWorkerBlockSignals</>来阻塞信号。
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</para>
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<!--==========================orignal english content==========================

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