vacuumdb: enable parallel mode

This mode allows vacuumdb to open several server connections to vacuum
or analyze several tables simultaneously.

Author: Dilip Kumar.  Some reworking by Álvaro Herrera
Reviewed by: Jeff Janes, Amit Kapila, Magnus Hagander, Andres Freund

doc/src/sgml/ref/vacuumdb.sgml

@@ -203,6 +203,30 @@ PostgreSQL documentation
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><option>-j <replaceable class="parameter">njobs</replaceable></option></term>
+      <term><option>--jobs=<replaceable class="parameter">njobs</replaceable></option></term>
+      <listitem>
+       <para>
+        Execute the vacuum or analyze commands in parallel by running
+        <replaceable class="parameter">njobs</replaceable>
+        commands simultaneously.  This option reduces the time of the
+        processing but it also increases the load on the database server.
+       </para>
+       <para>
+        <application>vacuumdb</application> will open
+        <replaceable class="parameter">njobs</replaceable> connections to the
+        database, so make sure your <xref linkend="guc-max-connections">
+        setting is high enough to accommodate all connections.
+       </para>
+       <para>
+        Note that using this mode together with the <option>-f</option>
+        (<literal>FULL</literal>) option might cause deadlock failures if
+        certain system catalogs are processed in parallel.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><option>--analyze-in-stages</option></term>
       <listitem>

src/bin/pg_dump/parallel.c

@@ -1160,7 +1160,7 @@ select_loop(int maxFd, fd_set *workerset)
 		i = select(maxFd + 1, workerset, NULL, NULL, NULL);
 
 		/*
-		 * If we Ctrl-C the master process , it's likely that we interrupt
+		 * If we Ctrl-C the master process, it's likely that we interrupt
 		 * select() here. The signal handler will set wantAbort == true and
 		 * the shutdown journey starts from here. Note that we'll come back
 		 * here later when we tell all workers to terminate and read their

src/bin/scripts/common.c

@@ -19,10 +19,9 @@
 
 #include "common.h"
 
-static void SetCancelConn(PGconn *conn);
-static void ResetCancelConn(void);
 
 static PGcancel *volatile cancelConn = NULL;
+bool CancelRequested = false;
 
 #ifdef WIN32
 static CRITICAL_SECTION cancelConnLock;
@@ -291,7 +290,7 @@ yesno_prompt(const char *question)
  *
  * Set cancelConn to point to the current database connection.
  */
-static void
+void
 SetCancelConn(PGconn *conn)
 {
 	PGcancel   *oldCancelConn;
@@ -321,7 +320,7 @@ SetCancelConn(PGconn *conn)
  *
  * Free the current cancel connection, if any, and set to NULL.
  */
-static void
+void
 ResetCancelConn(void)
 {
 	PGcancel   *oldCancelConn;
@@ -345,9 +344,8 @@ ResetCancelConn(void)
 
 #ifndef WIN32
 /*
- * Handle interrupt signals by canceling the current command,
- * if it's being executed through executeMaintenanceCommand(),
- * and thus has a cancelConn set.
+ * Handle interrupt signals by canceling the current command, if a cancelConn
+ * is set.
  */
 static void
 handle_sigint(SIGNAL_ARGS)
@@ -359,10 +357,15 @@ handle_sigint(SIGNAL_ARGS)
 	if (cancelConn != NULL)
 	{
 		if (PQcancel(cancelConn, errbuf, sizeof(errbuf)))
+		{
+			CancelRequested = true;
 			fprintf(stderr, _("Cancel request sent\n"));
+		}
 		else
 			fprintf(stderr, _("Could not send cancel request: %s"), errbuf);
 	}
+	else
+		CancelRequested = true;
 
 	errno = save_errno;			/* just in case the write changed it */
 }
@@ -392,10 +395,16 @@ consoleHandler(DWORD dwCtrlType)
 		if (cancelConn != NULL)
 		{
 			if (PQcancel(cancelConn, errbuf, sizeof(errbuf)))
+			{
 				fprintf(stderr, _("Cancel request sent\n"));
+				CancelRequested = true;
+			}
 			else
 				fprintf(stderr, _("Could not send cancel request: %s"), errbuf);
 		}
+		else
+			CancelRequested = true;
+
 		LeaveCriticalSection(&cancelConnLock);
 
 		return TRUE;

src/bin/scripts/common.h

@@ -21,6 +21,8 @@ enum trivalue
 	TRI_YES
 };
 
+extern bool CancelRequested;
+
 typedef void (*help_handler) (const char *progname);
 
 extern void handle_help_version_opts(int argc, char *argv[],
@@ -49,4 +51,8 @@ extern bool yesno_prompt(const char *question);
 
 extern void setup_cancel_handler(void);
 
+extern void SetCancelConn(PGconn *conn);
+extern void ResetCancelConn(void);
+
+
 #endif   /* COMMON_H */