[PoC PATCH] Parallel dump to /dev/null

From ff96d9f2984bb473ec6fdad779a09070a227d550 Mon Sep 17 00:00:00 2001
From: Michael Banck <michael.banck@credativ.de>
Date: Fri, 2 Feb 2018 15:02:26 +0100
Subject: [PATCH] WIP pg_dump TAP testcase

---
 src/bin/pg_dump/t/002_pg_dump.pl | 89 +++++++++++++++++++++++++++++++++++++---
 1 file changed, 84 insertions(+), 5 deletions(-)

diff --git a/src/bin/pg_dump/t/002_pg_dump.pl b/src/bin/pg_dump/t/002_pg_dump.pl
index 3e9b4d94dc..f8e64910b7 100644
--- a/src/bin/pg_dump/t/002_pg_dump.pl
+++ b/src/bin/pg_dump/t/002_pg_dump.pl
@@ -153,6 +153,12 @@ my %pgdump_runs = (
 			'--format=tar',
 			"--file=$tempdir/defaults_tar_format.sql",
 			"$tempdir/defaults_tar_format.tar", ], },
+
+	parallel_discard => {
+		dump_cmd => [
+			'pg_dump', '-Fd', '-j2', '--file=/dev/null',
+			'postgres', ], },
+
 	exclude_dump_test_schema => {
 		dump_cmd => [
 			'pg_dump', '--no-sync',
@@ -334,6 +340,7 @@ my %tests = (
 			exclude_dump_test_schema => 1,
 			no_privs                 => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -372,6 +379,7 @@ my %tests = (
 			no_privs                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -415,6 +423,7 @@ my %tests = (
 			no_privs                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -449,6 +458,7 @@ my %tests = (
 			no_owner                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			role                     => 1,
 			schema_only              => 1,
 			section_pre_data         => 1,
@@ -639,6 +649,7 @@ my %tests = (
 			section_post_data        => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			role                     => 1, }, },
 
 	'ALTER OPERATOR CLASS dump_test.op_class OWNER TO' => {
@@ -693,6 +704,7 @@ my %tests = (
 			no_owner                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -724,6 +736,7 @@ my %tests = (
 			no_owner                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -833,6 +846,7 @@ my %tests = (
 			data_only                => 1,
 			exclude_test_table       => 1,
 			exclude_dump_test_schema => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -866,6 +880,7 @@ my %tests = (
 			data_only                => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			section_data             => 1,
@@ -1059,6 +1074,7 @@ my %tests = (
 			no_blobs                 => 1,
 			no_privs                 => 1,
 			no_owner                 => 1,
+			parallel_discard         => 1,
 			pg_dumpall_dbprivs       => 1,
 			role                     => 1,
 			schema_only              => 1,
@@ -1128,6 +1144,7 @@ my %tests = (
 			no_privs                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_dbprivs       => 1,
 			schema_only              => 1,
 			section_pre_data         => 1,
@@ -1426,6 +1443,7 @@ qr/^ALTER (?!EVENT TRIGGER|LARGE OBJECT|PUBLICATION|SUBSCRIPTION)(.*) OWNER TO .
 			column_inserts           => 1,
 			data_only                => 1,
 			no_owner                 => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			section_data             => 1,
@@ -1438,6 +1456,7 @@ qr/^ALTER (?!EVENT TRIGGER|LARGE OBJECT|PUBLICATION|SUBSCRIPTION)(.*) OWNER TO .
 		like   => {},    # use more-specific options above
 		unlike => {
 			column_inserts           => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			section_data             => 1, }, },
@@ -1469,6 +1488,7 @@ qr/^ALTER (?!EVENT TRIGGER|LARGE OBJECT|PUBLICATION|SUBSCRIPTION)(.*) OWNER TO .
 			no_blobs                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -1505,6 +1525,7 @@ qr/^ALTER (?!EVENT TRIGGER|LARGE OBJECT|PUBLICATION|SUBSCRIPTION)(.*) OWNER TO .
 			no_blobs                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -1843,6 +1864,7 @@ qr/^COMMENT ON CONVERSION test_conversion IS 'comment on test conversion';/m,
 			no_blobs                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -1878,6 +1900,7 @@ qr/^COMMENT ON CONVERSION test_conversion IS 'comment on test conversion';/m,
 			data_only                => 1,
 			only_dump_test_table     => 1,
 			only_dump_test_schema    => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -1913,6 +1936,7 @@ qr/^COMMENT ON CONVERSION test_conversion IS 'comment on test conversion';/m,
 			data_only                => 1,
 			only_dump_test_table     => 1,
 			only_dump_test_schema    => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -2189,6 +2213,7 @@ qr/^COMMENT ON TEXT SEARCH TEMPLATE alt_ts_temp1 IS 'comment on text search temp
 		regexp   => qr/^COMMENT ON /m,
 		like     => {},                  # use more-specific options above
 		unlike   => {
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			section_data             => 1, }, },
@@ -2461,6 +2486,7 @@ qr/^COMMENT ON TEXT SEARCH TEMPLATE alt_ts_temp1 IS 'comment on text search temp
 		unlike   => {
 			binary_upgrade           => 1,
 			column_inserts           => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			schema_only              => 1,
@@ -2541,6 +2567,7 @@ qr/^\QINSERT INTO test_table_identity (col1, col2) OVERRIDING SYSTEM VALUE VALUE
 			section_data             => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			role                     => 1,
 			schema_only              => 1,
 			section_pre_data         => 1,
@@ -2574,6 +2601,7 @@ qr/^\QINSERT INTO test_table_identity (col1, col2) OVERRIDING SYSTEM VALUE VALUE
 			no_owner                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			role                     => 1,
 			schema_only              => 1,
 			section_pre_data         => 1,
@@ -2702,6 +2730,7 @@ qr/CREATE CAST \(timestamp with time zone AS interval\) WITH FUNCTION pg_catalog
 			no_owner                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_dbprivs       => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
@@ -2737,6 +2766,7 @@ qr/CREATE CAST \(timestamp with time zone AS interval\) WITH FUNCTION pg_catalog
 			no_owner                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -2770,6 +2800,7 @@ qr/CREATE CAST \(timestamp with time zone AS interval\) WITH FUNCTION pg_catalog
 			no_privs                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_dbprivs       => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
@@ -2822,6 +2853,7 @@ qr/CREATE CAST \(timestamp with time zone AS interval\) WITH FUNCTION pg_catalog
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -2857,6 +2889,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -2900,6 +2933,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -2941,6 +2975,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -2981,6 +3016,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3021,6 +3057,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3057,6 +3094,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3109,6 +3147,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3147,6 +3186,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3188,6 +3228,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			exclude_test_table       => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3227,6 +3268,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3258,6 +3300,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			no_privs                 => 1,
 			no_owner                 => 1,
 			only_dump_test_schema    => 1,
+			parallel_discard         => 1,
 			pg_dumpall_dbprivs       => 1,
 			schema_only              => 1,
 			section_pre_data         => 1,
@@ -3304,6 +3347,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3337,6 +3381,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3373,6 +3418,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3462,6 +3508,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3498,6 +3545,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3538,6 +3586,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3575,6 +3624,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3614,6 +3664,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3653,6 +3704,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3691,6 +3743,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3739,6 +3792,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3780,6 +3834,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3813,6 +3868,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3845,6 +3901,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3878,6 +3935,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3922,6 +3980,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3956,6 +4015,7 @@ qr/^\QCREATE DEFAULT CONVERSION test_conversion FOR 'LATIN1' TO 'UTF8' FROM iso8
 			data_only                => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -3991,6 +4051,7 @@ qr/CREATE TRANSFORM FOR integer LANGUAGE sql \(FROM SQL WITH FUNCTION pg_catalog
 			data_only                => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -4524,6 +4585,7 @@ qr/CREATE TRANSFORM FOR integer LANGUAGE sql \(FROM SQL WITH FUNCTION pg_catalog
 		unlike => {
 			column_inserts           => 1,
 			data_only                => 1,
+			parallel_discard         => 1,
 			role                     => 1,
 			section_data             => 1,
 			section_pre_data         => 1,
@@ -4559,6 +4621,7 @@ qr/CREATE TRANSFORM FOR integer LANGUAGE sql \(FROM SQL WITH FUNCTION pg_catalog
 			exclude_dump_test_schema => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			test_schema_plus_blobs   => 1, }, },
@@ -5379,9 +5442,10 @@ qr/CREATE TRANSFORM FOR integer LANGUAGE sql \(FROM SQL WITH FUNCTION pg_catalog
 		regexp   => qr/^CREATE /m,
 		like     => {},              # use more-specific options above
 		unlike   => {
-			column_inserts => 1,
-			data_only      => 1,
-			section_data   => 1, }, },
+			column_inserts   => 1,
+			data_only        => 1,
+			parallel_discard => 1,
+			section_data     => 1, }, },
 
 	'DROP SCHEMA public (for testing without public schema)' => {
 		all_runs     => 1,
@@ -5392,7 +5456,8 @@ qr/CREATE TRANSFORM FOR integer LANGUAGE sql \(FROM SQL WITH FUNCTION pg_catalog
 		like         => {},
 		unlike       => {
 			defaults_no_public       => 1,
-			defaults_no_public_clean => 1, } },
+			defaults_no_public_clean => 1,
+			parallel_discard         => 1, } },
 
 	'DROP SCHEMA public' => {
 		all_runs  => 1,
@@ -5434,6 +5499,7 @@ qr/CREATE TRANSFORM FOR integer LANGUAGE sql \(FROM SQL WITH FUNCTION pg_catalog
 		like   => { clean => 1, },
 		unlike => {
 			clean_if_exists          => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals_clean => 1, }, },
 
 	'DROP LANGUAGE pltestlang' => {
@@ -5618,6 +5684,7 @@ qr/CREATE TRANSFORM FOR integer LANGUAGE sql \(FROM SQL WITH FUNCTION pg_catalog
 			no_owner                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_dbprivs       => 1,
 			pg_dumpall_globals       => 1,
 			role                     => 1,
@@ -6293,6 +6360,7 @@ qr/^GRANT SELECT ON TABLE measurement_y2006m2 TO regress_dump_test_role;/m,
 			section_pre_data         => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
 			section_data             => 1,
@@ -6305,6 +6373,7 @@ qr/^GRANT SELECT ON TABLE measurement_y2006m2 TO regress_dump_test_role;/m,
 		like     => {},             # use more-specific options above
 		unlike   => {
 			no_privs                 => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals_clean => 1,
 			section_data             => 1,
 			section_post_data        => 1, }, },
@@ -6333,6 +6402,7 @@ qr/^GRANT SELECT ON TABLE measurement_y2006m2 TO regress_dump_test_role;/m,
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -6368,6 +6438,7 @@ qr/^GRANT SELECT ON TABLE measurement_y2006m2 TO regress_dump_test_role;/m,
 			data_only                => 1,
 			exclude_dump_test_schema => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
 			role                     => 1,
@@ -6397,6 +6468,7 @@ qr/^GRANT SELECT ON TABLE measurement_y2006m2 TO regress_dump_test_role;/m,
 			no_owner                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_dbprivs       => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
@@ -6430,6 +6502,7 @@ qr/^GRANT SELECT ON TABLE measurement_y2006m2 TO regress_dump_test_role;/m,
 			no_owner                 => 1,
 			only_dump_test_schema    => 1,
 			only_dump_test_table     => 1,
+			parallel_discard         => 1,
 			pg_dumpall_dbprivs       => 1,
 			pg_dumpall_globals       => 1,
 			pg_dumpall_globals_clean => 1,
@@ -6609,6 +6682,7 @@ qr/^GRANT SELECT ON TABLE measurement_y2006m2 TO regress_dump_test_role;/m,
 			column_inserts     => 1,
 			data_only          => 1,
 			no_privs           => 1,
+			parallel_discard   => 1,
 			pg_dumpall_globals => 1, }, },);
 
 #########################################
@@ -6845,7 +6919,12 @@ foreach my $run (sort keys %pgdump_runs)
 		$test_key = $pgdump_runs{$run}->{test_key};
 	}
 
-	my $output_file = slurp_file("$tempdir/${run}.sql");
+	my $output_file;
+
+	if (-f "$tempdir/${run}.sql")
+	{
+		$output_file = slurp_file("$tempdir/${run}.sql");
+	}
 
 	#########################################
 	# Run all tests where this run is included
-- 
2.14.2

diff --git a/src/bin/pg_dump/compress_io.c b/src/bin/pg_dump/compress_io.c
index a96da15dc1..8657ac30e6 100644
--- a/src/bin/pg_dump/compress_io.c
+++ b/src/bin/pg_dump/compress_io.c
@@ -512,7 +512,10 @@ cfopen_write(const char *path, const char *mode, int compression)
 #ifdef HAVE_LIBZ
 		char	   *fname;
 
-		fname = psprintf("%s.gz", path);
+		if (strcmp(path, NULL_DEVICE) != 0)
+			fname = psprintf("%s.gz", path);
+		else
+			fname = pg_strdup(path);
 		fp = cfopen(fname, mode, compression);
 		free_keep_errno(fname);
 #else
diff --git a/src/bin/pg_dump/pg_backup_archiver.h b/src/bin/pg_dump/pg_backup_archiver.h
index 8dd1915998..ab17adbc62 100644
--- a/src/bin/pg_dump/pg_backup_archiver.h
+++ b/src/bin/pg_dump/pg_backup_archiver.h
@@ -62,6 +62,13 @@ typedef struct _z_stream
 typedef z_stream *z_streamp;
 #endif
 
+/* Null device */
+#ifdef WIN32
+#define NULL_DEVICE "NUL"
+#else
+#define NULL_DEVICE "/dev/null"
+#endif
+
 /* Data block types */
 #define BLK_DATA 1
 #define BLK_BLOBS 3
diff --git a/src/bin/pg_dump/pg_backup_directory.c b/src/bin/pg_dump/pg_backup_directory.c
index 4aabb40f59..5936a799c7 100644
--- a/src/bin/pg_dump/pg_backup_directory.c
+++ b/src/bin/pg_dump/pg_backup_directory.c
@@ -54,6 +54,7 @@ typedef struct
 
 	cfp		   *blobsTocFH;		/* file handle for blobs.toc */
 	ParallelState *pstate;		/* for parallel backup / restore */
+	int			discard;		/* target is NULL_DEVICE */
 } lclContext;
 
 typedef struct
@@ -158,6 +159,11 @@ InitArchiveFmt_Directory(ArchiveHandle *AH)
 
 	ctx->directory = AH->fSpec;
 
+	if (strcmp(ctx->directory, NULL_DEVICE) == 0)
+		ctx->discard = 1;
+	else
+		ctx->discard = 0;
+
 	if (AH->mode == archModeWrite)
 	{
 		struct stat st;
@@ -192,9 +198,15 @@ InitArchiveFmt_Directory(ArchiveHandle *AH)
 			}
 		}
 
-		if (!is_empty && mkdir(ctx->directory, 0700) < 0)
-			exit_horribly(modulename, "could not create directory \"%s\": %s\n",
-						  ctx->directory, strerror(errno));
+		/*
+		 * Create the output directory, unless it exists already and is empty.
+		 * If we are discarding output to the null device, we must not
+		 * create it.
+		 */
+		if (!is_empty && !ctx->discard)
+			if (mkdir(ctx->directory, 0711) < 0)
+				exit_horribly(modulename, "could not create directory \"%s\": %s\n",
+							  ctx->directory, strerror(errno));
 	}
 	else
 	{							/* Read Mode */
@@ -602,8 +614,10 @@ _CloseArchive(ArchiveHandle *AH)
 		/*
 		 * In directory mode, there is no need to sync all the entries
 		 * individually. Just recurse once through all the files generated.
+		 * If we are discarding output to the null device, it does not
+		 * need syncing and would emit a warning if we did.
 		 */
-		if (AH->dosync)
+		if (AH->dosync && !ctx->discard)
 			fsync_dir_recurse(ctx->directory, progname);
 	}
 	AH->FH = NULL;
@@ -659,7 +673,14 @@ _StartBlob(ArchiveHandle *AH, TocEntry *te, Oid oid)
 	lclContext *ctx = (lclContext *) AH->formatData;
 	char		fname[MAXPGPATH];
 
-	snprintf(fname, MAXPGPATH, "%s/blob_%u.dat", ctx->directory, oid);
+	/*
+	 * If we are discarding output to the null device, just use that as
+	 * fname.
+	 */
+	if (ctx->discard)
+		snprintf(fname, MAXPGPATH, NULL_DEVICE);
+	else
+		snprintf(fname, MAXPGPATH, "%s/blob_%u.dat", ctx->directory, oid);
 
 	ctx->dataFH = cfopen_write(fname, PG_BINARY_W, AH->compression);
 
@@ -721,9 +742,18 @@ setFilePath(ArchiveHandle *AH, char *buf, const char *relativeFilename)
 	if (strlen(dname) + 1 + strlen(relativeFilename) + 1 > MAXPGPATH)
 		exit_horribly(modulename, "file name too long: \"%s\"\n", dname);
 
-	strcpy(buf, dname);
-	strcat(buf, "/");
-	strcat(buf, relativeFilename);
+	/*
+	 * If we are discarding output to the null device, we cannot set a file
+	 * path and just set the buffer to the null device.
+	 */
+	if (ctx->discard)
+	{
+		strcpy(buf, NULL_DEVICE);
+	} else {
+		strcpy(buf, dname);
+		strcat(buf, "/");
+		strcat(buf, relativeFilename);
+	}
 }
 
 /*

diff --git a/src/bin/pg_dump/compress_io.c b/src/bin/pg_dump/compress_io.c
index a96da15dc1..0953290069 100644
--- a/src/bin/pg_dump/compress_io.c
+++ b/src/bin/pg_dump/compress_io.c
@@ -512,7 +512,10 @@ cfopen_write(const char *path, const char *mode, int compression)
 #ifdef HAVE_LIBZ
 		char	   *fname;
 
-		fname = psprintf("%s.gz", path);
+		if (strcmp(path, DEVNULL) != 0)
+			fname = psprintf("%s.gz", path);
+		else
+			fname = pg_strdup(path);
 		fp = cfopen(fname, mode, compression);
 		free_keep_errno(fname);
 #else
diff --git a/src/bin/pg_dump/pg_backup_directory.c b/src/bin/pg_dump/pg_backup_directory.c
index 4aabb40f59..6aee04dad3 100644
--- a/src/bin/pg_dump/pg_backup_directory.c
+++ b/src/bin/pg_dump/pg_backup_directory.c
@@ -54,6 +54,7 @@ typedef struct
 
 	cfp		   *blobsTocFH;		/* file handle for blobs.toc */
 	ParallelState *pstate;		/* for parallel backup / restore */
+	int			discard;		/* target is DEVNULL */
 } lclContext;
 
 typedef struct
@@ -158,6 +159,11 @@ InitArchiveFmt_Directory(ArchiveHandle *AH)
 
 	ctx->directory = AH->fSpec;
 
+	if (strcmp(ctx->directory, DEVNULL) == 0)
+		ctx->discard = 1;
+	else
+		ctx->discard = 0;
+
 	if (AH->mode == archModeWrite)
 	{
 		struct stat st;
@@ -192,9 +198,15 @@ InitArchiveFmt_Directory(ArchiveHandle *AH)
 			}
 		}
 
-		if (!is_empty && mkdir(ctx->directory, 0700) < 0)
-			exit_horribly(modulename, "could not create directory \"%s\": %s\n",
-						  ctx->directory, strerror(errno));
+		/*
+		 * Create the output directory, unless it exists already and is empty.
+		 * If we are discarding output to the null device, we must not
+		 * create it.
+		 */
+		if (!is_empty && !ctx->discard)
+			if (mkdir(ctx->directory, 0711) < 0)
+				exit_horribly(modulename, "could not create directory \"%s\": %s\n",
+							  ctx->directory, strerror(errno));
 	}
 	else
 	{							/* Read Mode */
@@ -602,8 +614,10 @@ _CloseArchive(ArchiveHandle *AH)
 		/*
 		 * In directory mode, there is no need to sync all the entries
 		 * individually. Just recurse once through all the files generated.
+		 * If we are discarding output to the null device, it does not
+		 * need syncing and would emit a warning if we did.
 		 */
-		if (AH->dosync)
+		if (AH->dosync && !ctx->discard)
 			fsync_dir_recurse(ctx->directory, progname);
 	}
 	AH->FH = NULL;
@@ -659,7 +673,14 @@ _StartBlob(ArchiveHandle *AH, TocEntry *te, Oid oid)
 	lclContext *ctx = (lclContext *) AH->formatData;
 	char		fname[MAXPGPATH];
 
-	snprintf(fname, MAXPGPATH, "%s/blob_%u.dat", ctx->directory, oid);
+	/*
+	 * If we are discarding output to the null device, just use that as
+	 * fname.
+	 */
+	if (ctx->discard)
+		snprintf(fname, MAXPGPATH, DEVNULL);
+	else
+		snprintf(fname, MAXPGPATH, "%s/blob_%u.dat", ctx->directory, oid);
 
 	ctx->dataFH = cfopen_write(fname, PG_BINARY_W, AH->compression);
 
@@ -721,9 +742,18 @@ setFilePath(ArchiveHandle *AH, char *buf, const char *relativeFilename)
 	if (strlen(dname) + 1 + strlen(relativeFilename) + 1 > MAXPGPATH)
 		exit_horribly(modulename, "file name too long: \"%s\"\n", dname);
 
-	strcpy(buf, dname);
-	strcat(buf, "/");
-	strcat(buf, relativeFilename);
+	/*
+	 * If we are discarding output to the null device, we cannot set a file
+	 * path and just set the buffer to the null device.
+	 */
+	if (ctx->discard)
+	{
+		strcpy(buf, DEVNULL);
+	} else {
+		strcpy(buf, dname);
+		strcat(buf, "/");
+		strcat(buf, relativeFilename);
+	}
 }
 
 /*

diff --git a/src/bin/pg_dump/compress_io.c b/src/bin/pg_dump/compress_io.c
index a96da15dc1..0953290069 100644
--- a/src/bin/pg_dump/compress_io.c
+++ b/src/bin/pg_dump/compress_io.c
@@ -512,7 +512,10 @@ cfopen_write(const char *path, const char *mode, int compression)
 #ifdef HAVE_LIBZ
 		char	   *fname;
 
-		fname = psprintf("%s.gz", path);
+		if (strcmp(path, DEVNULL) != 0)
+			fname = psprintf("%s.gz", path);
+		else
+			fname = pg_strdup(path);
 		fp = cfopen(fname, mode, compression);
 		free_keep_errno(fname);
 #else
diff --git a/src/bin/pg_dump/pg_backup_directory.c b/src/bin/pg_dump/pg_backup_directory.c
index 4aabb40f59..3b77023d77 100644
--- a/src/bin/pg_dump/pg_backup_directory.c
+++ b/src/bin/pg_dump/pg_backup_directory.c
@@ -54,6 +54,7 @@ typedef struct
 
 	cfp		   *blobsTocFH;		/* file handle for blobs.toc */
 	ParallelState *pstate;		/* for parallel backup / restore */
+	bool		discard;		/* target is DEVNULL */
 } lclContext;
 
 typedef struct
@@ -158,6 +159,8 @@ InitArchiveFmt_Directory(ArchiveHandle *AH)
 
 	ctx->directory = AH->fSpec;
 
+	ctx->discard = strcmp(ctx->directory, DEVNULL) == 0;
+
 	if (AH->mode == archModeWrite)
 	{
 		struct stat st;
@@ -192,9 +195,15 @@ InitArchiveFmt_Directory(ArchiveHandle *AH)
 			}
 		}
 
-		if (!is_empty && mkdir(ctx->directory, 0700) < 0)
-			exit_horribly(modulename, "could not create directory \"%s\": %s\n",
-						  ctx->directory, strerror(errno));
+		/*
+		 * Create the output directory, unless it exists already and is empty.
+		 * If we are discarding output to the null device, we must not
+		 * create it.
+		 */
+		if (!is_empty && !ctx->discard)
+			if (mkdir(ctx->directory, 0700) < 0)
+				exit_horribly(modulename, "could not create directory \"%s\": %s\n",
+							  ctx->directory, strerror(errno));
 	}
 	else
 	{							/* Read Mode */
@@ -602,8 +611,10 @@ _CloseArchive(ArchiveHandle *AH)
 		/*
 		 * In directory mode, there is no need to sync all the entries
 		 * individually. Just recurse once through all the files generated.
+		 * If we are discarding output to the null device, it does not
+		 * need syncing and would emit a warning if we did.
 		 */
-		if (AH->dosync)
+		if (AH->dosync && !ctx->discard)
 			fsync_dir_recurse(ctx->directory, progname);
 	}
 	AH->FH = NULL;
@@ -659,7 +670,14 @@ _StartBlob(ArchiveHandle *AH, TocEntry *te, Oid oid)
 	lclContext *ctx = (lclContext *) AH->formatData;
 	char		fname[MAXPGPATH];
 
-	snprintf(fname, MAXPGPATH, "%s/blob_%u.dat", ctx->directory, oid);
+	/*
+	 * If we are discarding output to the null device, just use that as
+	 * fname.
+	 */
+	if (ctx->discard)
+		snprintf(fname, MAXPGPATH, DEVNULL);
+	else
+		snprintf(fname, MAXPGPATH, "%s/blob_%u.dat", ctx->directory, oid);
 
 	ctx->dataFH = cfopen_write(fname, PG_BINARY_W, AH->compression);
 
@@ -721,9 +739,18 @@ setFilePath(ArchiveHandle *AH, char *buf, const char *relativeFilename)
 	if (strlen(dname) + 1 + strlen(relativeFilename) + 1 > MAXPGPATH)
 		exit_horribly(modulename, "file name too long: \"%s\"\n", dname);
 
-	strcpy(buf, dname);
-	strcat(buf, "/");
-	strcat(buf, relativeFilename);
+	/*
+	 * If we are discarding output to the null device, we cannot set a file
+	 * path and just set the buffer to the null device.
+	 */
+	if (ctx->discard)
+		strcpy(buf, DEVNULL);
+	else
+	{
+		strcpy(buf, dname);
+		strcat(buf, "/");
+		strcat(buf, relativeFilename);
+	}
 }
 
 /*

From 5627c18f5a26ad8314f0590ce8ccf3b4093efb74 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Mon, 5 Mar 2018 13:42:29 -0300
Subject: [PATCH v5] Allow parallel dump to go to /dev/null

This is useful to quickly determine whether a dump would finish
without errors.

Author: Michael Banck
Discussion: https://postgr.es/m/20180201132446.GA13784@nighthawk.caipicrew.dd-dns.de
---
 src/bin/pg_dump/compress_io.c         |  8 +++++--
 src/bin/pg_dump/pg_backup_directory.c | 43 ++++++++++++++++++++++++++++-------
 2 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/src/bin/pg_dump/compress_io.c b/src/bin/pg_dump/compress_io.c
index a96da15dc1..a83b1e2ef5 100644
--- a/src/bin/pg_dump/compress_io.c
+++ b/src/bin/pg_dump/compress_io.c
@@ -496,7 +496,8 @@ cfopen_read(const char *path, const char *mode)
  *
  * If 'compression' is non-zero, a gzip compressed stream is opened, and
  * 'compression' indicates the compression level used. The ".gz" suffix
- * is automatically added to 'path' in that case.
+ * is automatically added to 'path' in that case (unless it's the null
+ * device).
  *
  * On failure, return NULL with an error code in errno.
  */
@@ -512,7 +513,10 @@ cfopen_write(const char *path, const char *mode, int compression)
 #ifdef HAVE_LIBZ
 		char	   *fname;
 
-		fname = psprintf("%s.gz", path);
+		if (strcmp(path, DEVNULL) != 0)
+			fname = psprintf("%s.gz", path);
+		else
+			fname = pg_strdup(path);
 		fp = cfopen(fname, mode, compression);
 		free_keep_errno(fname);
 #else
diff --git a/src/bin/pg_dump/pg_backup_directory.c b/src/bin/pg_dump/pg_backup_directory.c
index 4aabb40f59..3b77023d77 100644
--- a/src/bin/pg_dump/pg_backup_directory.c
+++ b/src/bin/pg_dump/pg_backup_directory.c
@@ -54,6 +54,7 @@ typedef struct
 
 	cfp		   *blobsTocFH;		/* file handle for blobs.toc */
 	ParallelState *pstate;		/* for parallel backup / restore */
+	bool		discard;		/* target is DEVNULL */
 } lclContext;
 
 typedef struct
@@ -158,6 +159,8 @@ InitArchiveFmt_Directory(ArchiveHandle *AH)
 
 	ctx->directory = AH->fSpec;
 
+	ctx->discard = strcmp(ctx->directory, DEVNULL) == 0;
+
 	if (AH->mode == archModeWrite)
 	{
 		struct stat st;
@@ -192,9 +195,15 @@ InitArchiveFmt_Directory(ArchiveHandle *AH)
 			}
 		}
 
-		if (!is_empty && mkdir(ctx->directory, 0700) < 0)
-			exit_horribly(modulename, "could not create directory \"%s\": %s\n",
-						  ctx->directory, strerror(errno));
+		/*
+		 * Create the output directory, unless it exists already and is empty.
+		 * If we are discarding output to the null device, we must not
+		 * create it.
+		 */
+		if (!is_empty && !ctx->discard)
+			if (mkdir(ctx->directory, 0700) < 0)
+				exit_horribly(modulename, "could not create directory \"%s\": %s\n",
+							  ctx->directory, strerror(errno));
 	}
 	else
 	{							/* Read Mode */
@@ -602,8 +611,10 @@ _CloseArchive(ArchiveHandle *AH)
 		/*
 		 * In directory mode, there is no need to sync all the entries
 		 * individually. Just recurse once through all the files generated.
+		 * If we are discarding output to the null device, it does not
+		 * need syncing and would emit a warning if we did.
 		 */
-		if (AH->dosync)
+		if (AH->dosync && !ctx->discard)
 			fsync_dir_recurse(ctx->directory, progname);
 	}
 	AH->FH = NULL;
@@ -659,7 +670,14 @@ _StartBlob(ArchiveHandle *AH, TocEntry *te, Oid oid)
 	lclContext *ctx = (lclContext *) AH->formatData;
 	char		fname[MAXPGPATH];
 
-	snprintf(fname, MAXPGPATH, "%s/blob_%u.dat", ctx->directory, oid);
+	/*
+	 * If we are discarding output to the null device, just use that as
+	 * fname.
+	 */
+	if (ctx->discard)
+		snprintf(fname, MAXPGPATH, DEVNULL);
+	else
+		snprintf(fname, MAXPGPATH, "%s/blob_%u.dat", ctx->directory, oid);
 
 	ctx->dataFH = cfopen_write(fname, PG_BINARY_W, AH->compression);
 
@@ -721,9 +739,18 @@ setFilePath(ArchiveHandle *AH, char *buf, const char *relativeFilename)
 	if (strlen(dname) + 1 + strlen(relativeFilename) + 1 > MAXPGPATH)
 		exit_horribly(modulename, "file name too long: \"%s\"\n", dname);
 
-	strcpy(buf, dname);
-	strcat(buf, "/");
-	strcat(buf, relativeFilename);
+	/*
+	 * If we are discarding output to the null device, we cannot set a file
+	 * path and just set the buffer to the null device.
+	 */
+	if (ctx->discard)
+		strcpy(buf, DEVNULL);
+	else
+	{
+		strcpy(buf, dname);
+		strcat(buf, "/");
+		strcat(buf, relativeFilename);
+	}
 }
 
 /*
-- 
2.11.0

diff --git a/src/bin/pg_dump/pg_backup_directory.c b/src/bin/pg_dump/pg_backup_directory.c
index 3b77023d77..4ffa6aaef2 100644
--- a/src/bin/pg_dump/pg_backup_directory.c
+++ b/src/bin/pg_dump/pg_backup_directory.c
@@ -55,6 +55,7 @@ typedef struct
 	cfp		   *blobsTocFH;		/* file handle for blobs.toc */
 	ParallelState *pstate;		/* for parallel backup / restore */
 	bool		discard;		/* target is DEVNULL */
+	bool		devnull_open;		/* whether DEVNULL has been opened as dataFH */
 } lclContext;
 
 typedef struct
@@ -340,10 +341,14 @@ _StartData(ArchiveHandle *AH, TocEntry *te)
 
 	setFilePath(AH, fname, tctx->filename);
 
-	ctx->dataFH = cfopen_write(fname, PG_BINARY_W, AH->compression);
-	if (ctx->dataFH == NULL)
-		exit_horribly(modulename, "could not open output file \"%s\": %s\n",
-					  fname, strerror(errno));
+	/* Open the file, unless we are discarding output to the null device */
+	if (!ctx->discard)
+	{
+		ctx->dataFH = cfopen_write(fname, PG_BINARY_W, AH->compression);
+		if (ctx->dataFH == NULL)
+			exit_horribly(modulename, "could not open output file \"%s\": %s\n",
+						  fname, strerror(errno));
+	}
 }
 
 /*
@@ -379,10 +384,13 @@ _EndData(ArchiveHandle *AH, TocEntry *te)
 {
 	lclContext *ctx = (lclContext *) AH->formatData;
 
-	/* Close the file */
-	cfclose(ctx->dataFH);
+	/* Close the file, unless we are discarding output to the null device */
+	if (!ctx->discard)
+	{
+		cfclose(ctx->dataFH);
 
-	ctx->dataFH = NULL;
+		ctx->dataFH = NULL;
+	}
 }
 
 /*
@@ -604,6 +612,14 @@ _CloseArchive(ArchiveHandle *AH)
 		if (cfclose(tocFH) != 0)
 			exit_horribly(modulename, "could not close TOC file: %s\n",
 						  strerror(errno));
+
+		/*
+		 * Open the DEVNULL special file for writing, we only need to open it
+		 * once.
+		 */
+		if (ctx->discard)
+			ctx->dataFH = cfopen_write(DEVNULL, PG_BINARY_W, 0);
+
 		WriteDataChunks(AH, ctx->pstate);
 
 		ParallelBackupEnd(AH, ctx->pstate);
@@ -657,6 +673,20 @@ _StartBlobs(ArchiveHandle *AH, TocEntry *te)
 	if (ctx->blobsTocFH == NULL)
 		exit_horribly(modulename, "could not open output file \"%s\": %s\n",
 					  fname, strerror(errno));
+
+	/*
+	 * If we are discarding output to the null device, open the dataFH here so
+	 * we do not have to open and close it for each blob.
+	 */
+	if (ctx->discard)
+	{
+		snprintf(fname, MAXPGPATH, DEVNULL);
+		ctx->dataFH = cfopen_write(fname, PG_BINARY_W, 0);
+
+		if (ctx->dataFH == NULL)
+			exit_horribly(modulename, "could not open output file \"%s\": %s\n",
+						  fname, strerror(errno));
+	}
 }
 
 /*
@@ -670,20 +700,16 @@ _StartBlob(ArchiveHandle *AH, TocEntry *te, Oid oid)
 	lclContext *ctx = (lclContext *) AH->formatData;
 	char		fname[MAXPGPATH];
 
-	/*
-	 * If we are discarding output to the null device, just use that as
-	 * fname.
-	 */
-	if (ctx->discard)
-		snprintf(fname, MAXPGPATH, DEVNULL);
-	else
+	if (!ctx->discard)
+	{
 		snprintf(fname, MAXPGPATH, "%s/blob_%u.dat", ctx->directory, oid);
 
-	ctx->dataFH = cfopen_write(fname, PG_BINARY_W, AH->compression);
+		ctx->dataFH = cfopen_write(fname, PG_BINARY_W, AH->compression);
 
-	if (ctx->dataFH == NULL)
-		exit_horribly(modulename, "could not open output file \"%s\": %s\n",
-					  fname, strerror(errno));
+		if (ctx->dataFH == NULL)
+			exit_horribly(modulename, "could not open output file \"%s\": %s\n",
+						  fname, strerror(errno));
+	}
 }
 
 /*
@@ -698,9 +724,12 @@ _EndBlob(ArchiveHandle *AH, TocEntry *te, Oid oid)
 	char		buf[50];
 	int			len;
 
-	/* Close the BLOB data file itself */
-	cfclose(ctx->dataFH);
-	ctx->dataFH = NULL;
+	if (!ctx->discard)
+	{
+		/* Close the BLOB data file itself */
+		cfclose(ctx->dataFH);
+		ctx->dataFH = NULL;
+	}
 
 	/* register the blob in blobs.toc */
 	len = snprintf(buf, sizeof(buf), "%u blob_%u.dat\n", oid, oid);
@@ -720,6 +749,12 @@ _EndBlobs(ArchiveHandle *AH, TocEntry *te)
 
 	cfclose(ctx->blobsTocFH);
 	ctx->blobsTocFH = NULL;
+
+	if (ctx->discard)
+	{
+		cfclose(ctx->dataFH);
+		ctx->dataFH = NULL;
+	}
 }
 
 /*
@@ -793,6 +828,14 @@ _DeClone(ArchiveHandle *AH)
 static int
 _WorkerJobDumpDirectory(ArchiveHandle *AH, TocEntry *te)
 {
+	lclContext *ctx = (lclContext *) AH->formatData;
+	if (ctx->discard)
+		if (!ctx->devnull_open)
+		{
+			ctx->dataFH = cfopen_write(DEVNULL, PG_BINARY_W, 0);
+			ctx->devnull_open = true;
+		}
+
 	/*
 	 * This function returns void. We either fail and die horribly or
 	 * succeed... A failure will be detected by the parent when the child dies