commit 393d47cf6b5ce77297e52e7fc390aa862fd2c2fd
Author: Jürgen Strobel <juergen+github@strobel.info>
Date:   Fri Mar 7 16:54:22 2014 +0100

    Add option --no-table-locks to pg_dump.

diff --git a/doc/src/sgml/ref/pg_dump.sgml b/doc/src/sgml/ref/pg_dump.sgml
index 1f0d4de..5725c46 100644
--- a/doc/src/sgml/ref/pg_dump.sgml
+++ b/doc/src/sgml/ref/pg_dump.sgml
@@ -772,6 +772,25 @@ PostgreSQL documentation
      </varlistentry>
 
      <varlistentry>
+      <term><option>--no-table-locks</></term>
+      <listitem>
+       <para>
+        If this option is specified, tables to be dumped will not be locked explicitly
+        at the start of pg_dump. It implies <option>--no-synchronized-snapshots</>.
+        This is potentially dangerous and should only be used by experts,
+        and only while there is no other activity in the database.
+       </para>
+       <para>
+        In the presense of an extreme number of tables pg_dump can exhibit
+        bad startup performance because it needs to issue LOCK TABLE statements for all
+        tables. This is intended as a last resort option for dump and restore version
+        upgrades, in order to make downtime manageable. In an especially bad case
+        with ~300000 tables this reduced dump time from 6 to 1 hours.
+       </para>
+      </listitem>
+     </varlistentry>
+
+     <varlistentry>
       <term><option>--no-tablespaces</option></term>
       <listitem>
        <para>
diff --git a/src/bin/pg_dump/parallel.c b/src/bin/pg_dump/parallel.c
index 6f2634b..ac05356 100644
--- a/src/bin/pg_dump/parallel.c
+++ b/src/bin/pg_dump/parallel.c
@@ -32,6 +32,9 @@
 #define PIPE_READ							0
 #define PIPE_WRITE							1
 
+/* flag for the no-table-locks command-line long option */
+int	no_table_locks = 0;
+
 /* file-scope variables */
 #ifdef WIN32
 static unsigned int tMasterThreadId = 0;
@@ -886,7 +889,7 @@ WaitForCommands(ArchiveHandle *AH, int pipefd[2])
 			 * meantime.  lockTableNoWait dies in this case to prevent a
 			 * deadlock.
 			 */
-			if (strcmp(te->desc, "BLOBS") != 0)
+			if (!no_table_locks && strcmp(te->desc, "BLOBS") != 0)
 				lockTableNoWait(AH, te);
 
 			/*
diff --git a/src/bin/pg_dump/parallel.h b/src/bin/pg_dump/parallel.h
index 7a32a9b..f95a6bb 100644
--- a/src/bin/pg_dump/parallel.h
+++ b/src/bin/pg_dump/parallel.h
@@ -70,6 +70,9 @@ extern bool parallel_init_done;
 extern DWORD mainThreadId;
 #endif
 
+/* flag for the no-table-locks command-line long option */
+extern int	no_table_locks;
+
 extern void init_parallel_dump_utils(void);
 
 extern int	GetIdleWorker(ParallelState *pstate);
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 17bb846..e1fe047 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -357,6 +357,7 @@ main(int argc, char **argv)
 		{"use-set-session-authorization", no_argument, &use_setsessauth, 1},
 		{"no-security-labels", no_argument, &no_security_labels, 1},
 		{"no-synchronized-snapshots", no_argument, &no_synchronized_snapshots, 1},
+		{"no-table-locks", no_argument, &no_table_locks, 1},
 		{"no-unlogged-table-data", no_argument, &no_unlogged_table_data, 1},
 
 		{NULL, 0, NULL, 0}
@@ -562,6 +563,10 @@ main(int argc, char **argv)
 	if (column_inserts)
 		dump_inserts = 1;
 
+	/* --no-table-locks implies --no_synchronized_snapshots */
+	if (no_table_locks)
+		no_synchronized_snapshots = 1;
+
 	if (dataOnly && schemaOnly)
 	{
 		write_msg(NULL, "options -s/--schema-only and -a/--data-only cannot be used together\n");
@@ -902,6 +907,7 @@ help(const char *progname)
 	printf(_("  --inserts                    dump data as INSERT commands, rather than COPY\n"));
 	printf(_("  --no-security-labels         do not dump security label assignments\n"));
 	printf(_("  --no-synchronized-snapshots  do not use synchronized snapshots in parallel jobs\n"));
+	printf(_("  --no-table-locks             do not lock tables before starting to dump\n"));
 	printf(_("  --no-tablespaces             do not dump tablespace assignments\n"));
 	printf(_("  --no-unlogged-table-data     do not dump unlogged table data\n"));
 	printf(_("  --quote-all-identifiers      quote all identifiers, even if not key words\n"));
@@ -4807,7 +4813,7 @@ getTables(Archive *fout, int *numTables)
 		 * NOTE: it'd be kinda nice to lock other relations too, not only
 		 * plain tables, but the backend doesn't presently allow that.
 		 */
-		if (tblinfo[i].dobj.dump && tblinfo[i].relkind == RELKIND_RELATION)
+		if (!no_table_locks && tblinfo[i].dobj.dump && tblinfo[i].relkind == RELKIND_RELATION)
 		{
 			resetPQExpBuffer(query);
 			appendPQExpBuffer(query,