Add parallel pg_dump option.

New infrastructure is added which creates a set number of workers
(threads on Windows, forked processes on Unix). Jobs are then
handed out to these workers by the master process as needed.
pg_restore is adjusted to use this new infrastructure in place of the
old setup which created a new worker for each step on the fly. Parallel
dumps acquire a snapshot clone in order to stay consistent, if
available.

The parallel option is selected by the -j / --jobs command line
parameter of pg_dump.

Joachim Wieland, lightly editorialized by Andrew Dunstan.

src/bin/pg_dump/dumputils.c

@@ -38,6 +38,7 @@ static struct
 }	on_exit_nicely_list[MAX_ON_EXIT_NICELY];
 
 static int	on_exit_nicely_index;
+void		(*on_exit_msg_func) (const char *modulename, const char *fmt, va_list ap) = vwrite_msg;
 
 #define supports_grant_options(version) ((version) >= 70400)
 
@@ -48,11 +49,21 @@ static bool parseAclItem(const char *item, const char *type,
 static char *copyAclUserName(PQExpBuffer output, char *input);
 static void AddAcl(PQExpBuffer aclbuf, const char *keyword,
 	   const char *subname);
+static PQExpBuffer getThreadLocalPQExpBuffer(void);
 
 #ifdef WIN32
+static void shutdown_parallel_dump_utils(int code, void *unused);
 static bool parallel_init_done = false;
 static DWORD tls_index;
 static DWORD mainThreadId;
+
+static void
+shutdown_parallel_dump_utils(int code, void *unused)
+{
+	/* Call the cleanup function only from the main thread */
+	if (mainThreadId == GetCurrentThreadId())
+		WSACleanup();
+}
 #endif
 
 void
@@ -61,23 +72,29 @@ init_parallel_dump_utils(void)
 #ifdef WIN32
 	if (!parallel_init_done)
 	{
+		WSADATA		wsaData;
+		int			err;
+
 		tls_index = TlsAlloc();
-		parallel_init_done = true;
 		mainThreadId = GetCurrentThreadId();
+		err = WSAStartup(MAKEWORD(2, 2), &wsaData);
+		if (err != 0)
+		{
+			fprintf(stderr, _("WSAStartup failed: %d\n"), err);
+			exit_nicely(1);
+		}
+		on_exit_nicely(shutdown_parallel_dump_utils, NULL);
+		parallel_init_done = true;
 	}
 #endif
 }
 
 /*
- *	Quotes input string if it's not a legitimate SQL identifier as-is.
- *
- *	Note that the returned string must be used before calling fmtId again,
- *	since we re-use the same return buffer each time.  Non-reentrant but
- *	reduces memory leakage. (On Windows the memory leakage will be one buffer
- *	per thread, which is at least better than one per call).
+ * Non-reentrant but reduces memory leakage. (On Windows the memory leakage
+ * will be one buffer per thread, which is at least better than one per call).
  */
-const char *
-fmtId(const char *rawid)
+static PQExpBuffer
+getThreadLocalPQExpBuffer(void)
 {
 	/*
 	 * The Tls code goes awry if we use a static var, so we provide for both
@@ -86,9 +103,6 @@ fmtId(const char *rawid)
 	static PQExpBuffer s_id_return = NULL;
 	PQExpBuffer id_return;
 
-	const char *cp;
-	bool		need_quotes = false;
-
 #ifdef WIN32
 	if (parallel_init_done)
 		id_return = (PQExpBuffer) TlsGetValue(tls_index);		/* 0 when not set */
@@ -118,6 +132,23 @@ fmtId(const char *rawid)
 
 	}
 
+	return id_return;
+}
+
+/*
+ *	Quotes input string if it's not a legitimate SQL identifier as-is.
+ *
+ *	Note that the returned string must be used before calling fmtId again,
+ *	since we re-use the same return buffer each time.
+ */
+const char *
+fmtId(const char *rawid)
+{
+	PQExpBuffer id_return = getThreadLocalPQExpBuffer();
+
+	const char *cp;
+	bool		need_quotes = false;
+
 	/*
 	 * These checks need to match the identifier production in scan.l. Don't
 	 * use islower() etc.
@@ -185,6 +216,35 @@ fmtId(const char *rawid)
 	return id_return->data;
 }
 
+/*
+ * fmtQualifiedId - convert a qualified name to the proper format for
+ * the source database.
+ *
+ * Like fmtId, use the result before calling again.
+ *
+ * Since we call fmtId and it also uses getThreadLocalPQExpBuffer() we cannot
+ * use it until we're finished with calling fmtId().
+ */
+const char *
+fmtQualifiedId(int remoteVersion, const char *schema, const char *id)
+{
+	PQExpBuffer id_return;
+	PQExpBuffer lcl_pqexp = createPQExpBuffer();
+
+	/* Suppress schema name if fetching from pre-7.3 DB */
+	if (remoteVersion >= 70300 && schema && *schema)
+	{
+		appendPQExpBuffer(lcl_pqexp, "%s.", fmtId(schema));
+	}
+	appendPQExpBuffer(lcl_pqexp, "%s", fmtId(id));
+
+	id_return = getThreadLocalPQExpBuffer();
+
+	appendPQExpBuffer(id_return, "%s", lcl_pqexp->data);
+	destroyPQExpBuffer(lcl_pqexp);
+
+	return id_return->data;
+}
 
 /*
  * Convert a string value to an SQL string literal and append it to
@@ -1315,7 +1375,7 @@ exit_horribly(const char *modulename, const char *fmt,...)
 	va_list		ap;
 
 	va_start(ap, fmt);
-	vwrite_msg(modulename, fmt, ap);
+	on_exit_msg_func(modulename, fmt, ap);
 	va_end(ap);
 
 	exit_nicely(1);