# Copyright (c) 2022, PostgreSQL Global Development Group

# Test recovering to a point-in-time using WAL archive, such that the
# target point is physically in a WAL segment with a higher TLI than
# the target point's TLI.  For example, imagine that the following WAL
# segments exist in the WAL archive:
#
#      000000010000000000000001
#      000000010000000000000002
#      000000020000000000000003
#
# The timeline switch happened in the middle of WAL segment 3, but it
# was never archived on timeline 1.  The first half of
# 000000020000000000000003 contains the WAL from timeline 1 up to the
# point where the timeline switch happened.  If you now perform
# archive recovery with recovery target point in that first half of
# segment 3, archive recovery will find the WAL up to that point in
# segment 000000020000000000000003, but it will not follow the
# timeline switch to timeline 2, and creates a timeline switching
# end-of-recovery record with TLI 1 -> 3.  That's what this test case
# tests.
#
# The comments below contain lists of WAL segments at different points
# in the tests, to make it easier to follow along.  They are correct
# as of this writing, but the exact WAL segment numbers could change
# if the backend logic for when it switches to a new segment changes.
# The actual checks are not sensitive to that.

use strict;
use warnings;
use PostgreSQL::Test::Cluster;
use PostgreSQL::Test::Utils;
use Test::More;
use File::Compare;

# Initialize and start primary node with WAL archiving
my $node_primary = PostgreSQL::Test::Cluster->new('primary');
$node_primary->init(has_archiving => 1, allows_streaming => 1);
$node_primary->start;

# Take a backup.
my $backup_name = 'my_backup';
$node_primary->backup($backup_name);

# Workload with some transactions, and the target restore point.
$node_primary->psql(
	'postgres', qq{
CREATE TABLE foo(i int);
INSERT INTO foo VALUES(1);
SELECT pg_create_restore_point('rp');
INSERT INTO foo VALUES(2);
});

# Contents of the WAL archive at this point:
#
# 000000010000000000000001
# 000000010000000000000002
# 000000010000000000000002.00000028.backup
#
# The operations on the test table and the restore point went into WAL
# segment 3, but it hasn't been archived yet.

# Start a standby node, and wait for it to catch up.
my $node_standby = PostgreSQL::Test::Cluster->new('standby');
$node_standby->init_from_backup(
	$node_primary, $backup_name,
	standby       => 1,
	has_streaming => 1,
	has_archiving => 1,
	has_restoring => 0);
$node_standby->append_conf('postgresql.conf', 'archive_mode = always');
$node_standby->start;
$node_primary->wait_for_catchup($node_standby);

# Check that it's really caught up.
my $result = $node_standby->safe_psql('postgres', "SELECT max(i) FROM foo;");
is($result, qq{2}, "check table contents after archive recovery");

# Kill the old primary, before it archives the most recent WAL segment that
# contains all the INSERTs.
$node_primary->stop('immediate');

# Promote the standby, and switch WAL so that it archives a WAL segment
# that contains all the INSERTs, on a new timeline.
$node_standby->promote;

# Find next WAL segment to be archived.
my $walfile_to_be_archived = $node_standby->safe_psql('postgres',
	"SELECT pg_walfile_name(pg_current_wal_lsn());");

# Make WAL segment eligible for archival
$node_standby->safe_psql('postgres', 'SELECT pg_switch_wal()');

# We don't need the standby anymore, request shutdown. The server will
# finish archiving all the WAL on timeline 2 before it exits.
$node_standby->stop;

# Contents of the WAL archive at this point:
#
# 000000010000000000000001
# 000000010000000000000002
# 000000010000000000000002.00000028.backup
# 000000010000000000000003.partial
# 000000020000000000000003
# 00000002.history
#
# The operations on the test table and the restore point are in
# segment 3.  They are part of timeline 1, but were not archived by
# the primary yet.  However, they were copied into the beginning of
# segment 000000020000000000000003, before the timeline switching
# record.  (They are also present in the
# 000000010000000000000003.partial file, but .partial files are not
# used automatically.)

# Now test PITR to the recovery target.  It should find the WAL in
# segment 000000020000000000000003, but not follow the timeline switch
# to timeline 2.
my $node_pitr = PostgreSQL::Test::Cluster->new('node_pitr');
$node_pitr->init_from_backup(
	$node_primary, $backup_name,
	standby       => 0,
	has_restoring => 1);
$node_pitr->append_conf(
	'postgresql.conf', qq{
recovery_target_name = 'rp'
recovery_target_action = 'promote'
});

$node_pitr->start;

# Wait until recovery finishes.
$node_pitr->poll_query_until('postgres', "SELECT pg_is_in_recovery() = 'f';")
  or die "Timed out while waiting for PITR promotion";

# Check that we see the data we expect.
$result = $node_pitr->safe_psql('postgres', "SELECT max(i) FROM foo;");
is($result, qq{1}, "check table contents after point-in-time recovery");

# Insert a row so that we can check later that we successfully recover
# back to this timeline.
$node_pitr->safe_psql('postgres', "INSERT INTO foo VALUES(3);");

# Wait for the archiver to be running.  The startup process might have yet to
# exit, in which case the postmaster has not started the archiver.  If we
# stop() without an archiver, the archive will be incomplete.
$node_pitr->poll_query_until('postgres',
	"SELECT true FROM pg_stat_activity WHERE backend_type = 'archiver';")
  or die "Timed out while waiting for archiver to start";

# Stop the node.  This archives the last segment.
$node_pitr->stop();

# Test archive recovery on the timeline created by the PITR.  This
# replays the end-of-recovery record that switches from timeline 1 to
# 3.
my $node_pitr2 = PostgreSQL::Test::Cluster->new('node_pitr2');
$node_pitr2->init_from_backup(
	$node_primary, $backup_name,
	standby       => 0,
	has_restoring => 1);
$node_pitr2->append_conf(
	'postgresql.conf', qq{
recovery_target_action = 'promote'
});

$node_pitr2->start;

# Wait until recovery finishes.
$node_pitr2->poll_query_until('postgres', "SELECT pg_is_in_recovery() = 'f';")
  or die "Timed out while waiting for PITR promotion";

# Verify that we can see the row inserted after the PITR.
$result = $node_pitr2->safe_psql('postgres', "SELECT max(i) FROM foo;");
is($result, qq{3}, "check table contents after point-in-time recovery");

done_testing();
