Exclude pg_internal.init from BASE_BACKUP

Add docs to explain this for other backup mechanisms

Author: David Steele <david@pgmasters.net>
Reviewed-by: Petr Jelinek <petr.jelinek@2ndQuadrant.com> et al

Author: simonat2ndQuadrant

doc/src/sgml/backup.sgml

@@ -1129,6 +1129,12 @@ SELECT pg_stop_backup();
     the directories will be recreated as needed.
    </para>
 
+   <para>
+    <filename>pg_internal.init</filename> files can be omitted from the
+    backup whenever a file of that name is found.  These files contain
+    relation cache data that is always rebuilt when recovering.
+   </para>
+
    <para>
     The backup label
     file includes the label string you gave to <function>pg_start_backup</function>,

doc/src/sgml/protocol.sgml

@@ -2499,6 +2499,11 @@ The commands accepted in walsender mode are:
          <filename>postmaster.opts</filename>
         </para>
        </listitem>
+       <listitem>
+        <para>
+         <filename>pg_internal.init (found in multiple directories)</>
+        </para>
+       </listitem>
        <listitem>
         <para>
          Various temporary files and directories created during the operation

src/backend/replication/basebackup.c

@@ -36,6 +36,7 @@
 #include "utils/builtins.h"
 #include "utils/elog.h"
 #include "utils/ps_status.h"
+#include "utils/relcache.h"
 #include "utils/timestamp.h"
 
 
@@ -151,6 +152,9 @@ static const char *excludeFiles[] =
 	/* Skip current log file temporary file */
 	LOG_METAINFO_DATAFILE_TMP,
 
+	/* Skip relation cache because it is rebuilt on startup */
+	RELCACHE_INIT_FILENAME,
+
 	/*
 	 * If there's a backup_label or tablespace_map file, it belongs to a
 	 * backup started by the user with pg_start_backup().  It is *not* correct

src/backend/utils/cache/relcache.c

@@ -87,11 +87,6 @@
 #include "utils/tqual.h"
 
 
-/*
- *		name of relcache init file(s), used to speed up backend startup
- */
-#define RELCACHE_INIT_FILENAME	"pg_internal.init"
-
 #define RELCACHE_INIT_FILEMAGIC		0x573266	/* version ID value */
 
 /*

src/bin/pg_basebackup/t/010_pg_basebackup.pl

@@ -4,7 +4,7 @@
 use Config;
 use PostgresNode;
 use TestLib;
-use Test::More tests => 78;
+use Test::More tests => 79;
 
 program_help_ok('pg_basebackup');
 program_version_ok('pg_basebackup');
@@ -61,6 +61,11 @@
 	close $file;
 }
 
+# Connect to a database to create global/pg_internal.init.  If this is removed
+# the test to ensure global/pg_internal.init is not copied will return a false
+# positive.
+$node->safe_psql('postgres', 'SELECT 1;');
+
 $node->command_ok([ 'pg_basebackup', '-D', "$tempdir/backup", '-X', 'none' ],
 	'pg_basebackup runs');
 ok(-f "$tempdir/backup/PG_VERSION", 'backup was created');
@@ -84,7 +89,8 @@
 
 # These files should not be copied.
 foreach my $filename (
-	qw(postgresql.auto.conf.tmp postmaster.opts postmaster.pid tablespace_map current_logfiles.tmp)
+	qw(postgresql.auto.conf.tmp postmaster.opts postmaster.pid tablespace_map current_logfiles.tmp
+		global/pg_internal.init)
   )
 {
 	ok(!-f "$tempdir/backup/$filename", "$filename not copied");

src/include/utils/relcache.h

@@ -18,6 +18,11 @@
 #include "nodes/bitmapset.h"
 
 
+/*
+ * Name of relcache init file(s), used to speed up backend startup
+ */
+#define RELCACHE_INIT_FILENAME	"pg_internal.init"
+
 typedef struct RelationData *Relation;
 
 /* ----------------