pg_dump: Allow dumping data of specific foreign servers

The new command-line switch --include-foreign-data=PATTERN lets the user
specify foreign servers from which to dump foreign table data.  This can
be refined by further inclusion/exclusion switches, so that the user has
full control over which tables to dump.

A limitation is that this doesn't work in combination with parallel
dumps, for implementation reasons.  This might be lifted in the future,
but requires shuffling some code around.

Author: Luis Carril <luis.carril@swarm64.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Surafel Temesgen <surafel3000@gmail.com>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Reviewed-by: Álvaro Herrera <alvherre@2ndQuadrant.com>
Discussion: https://postgr.es/m/LEJPR01MB0185483C0079D2F651B16231E7FC0@LEJPR01MB0185.DEUPRD01.PROD.OUTLOOK.DE

doc/src/sgml/ref/pg_dump.sgml

@@ -767,6 +767,36 @@ PostgreSQL documentation
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><option>--include-foreign-data=<replaceable class="parameter">foreignserver</replaceable></option></term>
+      <listitem>
+       <para>
+        Dump the data for any foreign table with a foreign server
+        matching <replaceable class="parameter">foreignserver</replaceable>
+        pattern. Multiple foreign servers can be selected by writing multiple
+        <option>--include-foreign-data</option> switches.
+        Also, the <replaceable class="parameter">foreignserver</replaceable> parameter is
+        interpreted as a pattern according to the same rules used by
+        <application>psql</application>'s <literal>\d</literal> commands (see <xref
+        linkend="app-psql-patterns" endterm="app-psql-patterns-title"/>),
+        so multiple foreign servers can also be selected by writing wildcard characters
+        in the pattern.  When using wildcards, be careful to quote the pattern
+        if needed to prevent the shell from expanding the wildcards; see
+        <xref linkend="pg-dump-examples" endterm="pg-dump-examples-title"/>.
+        The only exception is that an empty pattern is disallowed.
+       </para>
+
+       <note>
+        <para>
+         When <option>--include-foreign-data</option> is specified,
+         <application>pg_dump</application> does not check that the foreign
+         table is writeable.  Therefore, there is no guarantee that the
+         results of a foreign table dump can be successfully restored.
+        </para>
+       </note>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <term><option>--inserts</option></term>
       <listitem>

src/bin/pg_dump/pg_dump.h

@@ -283,6 +283,7 @@ typedef struct _tableInfo
 	uint32		toast_minmxid;	/* toast table's relminmxid */
 	int			ncheck;			/* # of CHECK expressions */
 	char	   *reloftype;		/* underlying type for typed table */
+	Oid			foreign_server; /* foreign server oid, if applicable */
 	/* these two are set only if table is a sequence owned by a column: */
 	Oid			owning_tab;		/* OID of table owning sequence */
 	int			owning_col;		/* attr # of column owning sequence */

src/bin/pg_dump/t/001_basic.pl

@@ -4,7 +4,7 @@ use warnings;
 use Config;
 use PostgresNode;
 use TestLib;
-use Test::More tests => 74;
+use Test::More tests => 78;
 
 my $tempdir       = TestLib::tempdir;
 my $tempdir_short = TestLib::tempdir_short;
@@ -49,6 +49,18 @@ command_fails_like(
 	'pg_dump: options -s/--schema-only and -a/--data-only cannot be used together'
 );
 
+command_fails_like(
+	[ 'pg_dump', '-s', '--include-foreign-data=xxx' ],
+	qr/\Qpg_dump: error: options -s\/--schema-only and --include-foreign-data cannot be used together\E/,
+	'pg_dump: options -s/--schema-only and --include-foreign-data cannot be used together'
+);
+
+command_fails_like(
+	[ 'pg_dump', '-j2', '--include-foreign-data=xxx' ],
+	qr/\Qpg_dump: error: option --include-foreign-data is not supported with parallel backup\E/,
+	'pg_dump: option --include-foreign-data is not supported with parallel backup'
+);
+
 command_fails_like(
 	['pg_restore'],
 	qr{\Qpg_restore: error: one of -d/--dbname and -f/--file must be specified\E},

src/bin/pg_dump/t/003_pg_dump_with_server.pl

+use strict;
+use warnings;
+
+use PostgresNode;
+use TestLib;
+use Test::More tests => 3;
+
+my $tempdir       = TestLib::tempdir;
+my $tempdir_short = TestLib::tempdir_short;
+
+my $node = get_new_node('main');
+my $port = $node->port;
+
+$node->init;
+$node->start;
+
+#########################################
+# Verify that dumping foreign data includes only foreign tables of
+# matching servers
+
+$node->safe_psql( 'postgres', "CREATE FOREIGN DATA WRAPPER dummy");
+$node->safe_psql( 'postgres', "CREATE SERVER s0 FOREIGN DATA WRAPPER dummy");
+$node->safe_psql( 'postgres', "CREATE SERVER s1 FOREIGN DATA WRAPPER dummy");
+$node->safe_psql( 'postgres', "CREATE SERVER s2 FOREIGN DATA WRAPPER dummy");
+$node->safe_psql( 'postgres', "CREATE FOREIGN TABLE t0 (a int) SERVER s0");
+$node->safe_psql( 'postgres', "CREATE FOREIGN TABLE t1 (a int) SERVER s1");
+my ($cmd, $stdout, $stderr, $result);
+
+command_fails_like(
+	[ "pg_dump",  '-p', $port, 'postgres', '--include-foreign-data=s0' ],
+	qr/foreign-data wrapper \"dummy\" has no handler\r?\npg_dump: error: query was:.*t0/,
+	"correctly fails to dump a foreign table from a dummy FDW");
+
+command_ok(
+	[ "pg_dump", '-p', $port, 'postgres', '-a', '--include-foreign-data=s2' ] ,
+	"dump foreign server with no tables");