Create common infrastructure for cross-version upgrade testing.

To test pg_upgrade across major PG versions, we have to be able to
modify or drop any old objects with no-longer-supported properties,
and we have to be able to deal with cosmetic changes in pg_dump output.
Up to now, the buildfarm and pg_upgrade's own test infrastructure had
separate implementations of the former, and we had nothing but very
ad-hoc rules for the latter (including an arbitrary threshold on how
many lines of unchecked diff were okay!).  This patch creates a Perl
module that can be shared by both those use-cases, and adds logic
that deals with pg_dump output diffs in a much more tightly defined
fashion.

This largely supersedes previous efforts in commits 0df9641d3,
9814ff550, and 62be9e4cd, which developed a SQL-script-based solution
for the task of dropping old objects.  There was nothing fundamentally
wrong with that work in itself, but it had no basis for solving the
output-formatting problem.  The most plausible way to deal with
formatting is to build a Perl module that can perform editing on the
dump files; and once we commit to that, it makes more sense for the
same module to also embed the knowledge of what has to be done for
dropping old objects.

Back-patch versions of the helper module as far as 9.2, to
support buildfarm animals that still test that far back.
It's also necessary to back-patch PostgreSQL/Version.pm,
because the new code depends on that.  I fixed up pg_upgrade's
002_pg_upgrade.pl in v15, but did not look into back-patching
it further than that.

Tom Lane and Andrew Dunstan

Discussion: https://postgr.es/m/891521.1673657296@sss.pgh.pa.us

src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm

@@ -0,0 +1,293 @@
+
+# Copyright (c) 2023, PostgreSQL Global Development Group
+
+=pod
+
+=head1 NAME
+
+PostgreSQL::Test::AdjustUpgrade - helper module for cross-version upgrade tests
+
+=head1 SYNOPSIS
+
+  use PostgreSQL::Test::AdjustUpgrade;
+
+  # Build commands to adjust contents of old-version database before dumping
+  $statements = adjust_database_contents($old_version, %dbnames);
+
+  # Adjust contents of old pg_dumpall output file to match newer version
+  $dump = adjust_old_dumpfile($old_version, $dump);
+
+  # Adjust contents of new pg_dumpall output file to match older version
+  $dump = adjust_new_dumpfile($old_version, $dump);
+
+=head1 DESCRIPTION
+
+C<PostgreSQL::Test::AdjustUpgrade> encapsulates various hacks needed to
+compare the results of cross-version upgrade tests.
+
+=cut
+
+package PostgreSQL::Test::AdjustUpgrade;
+
+use strict;
+use warnings;
+
+use Exporter 'import';
+use PostgreSQL::Version;
+
+our @EXPORT = qw(
+  adjust_database_contents
+  adjust_old_dumpfile
+  adjust_new_dumpfile
+);
+
+=pod
+
+=head1 ROUTINES
+
+=over
+
+=item $statements = adjust_database_contents($old_version, %dbnames)
+
+Generate SQL commands to perform any changes to an old-version installation
+that are needed before we can pg_upgrade it into the current PostgreSQL
+version.
+
+Typically this involves dropping or adjusting no-longer-supported objects.
+
+Arguments:
+
+=over
+
+=item C<old_version>: Branch we are upgrading from, represented as a
+PostgreSQL::Version object.
+
+=item C<dbnames>: Hash of database names present in the old installation.
+
+=back
+
+Returns a reference to a hash, wherein the keys are database names and the
+values are arrayrefs to lists of statements to be run in those databases.
+
+=cut
+
+sub adjust_database_contents
+{
+	my ($old_version, %dbnames) = @_;
+	my $result = {};
+
+	# remove dbs of modules known to cause pg_upgrade to fail
+	# anything not builtin and incompatible should clean up its own db
+	foreach my $bad_module ('test_ddl_deparse', 'tsearch2')
+	{
+		if ($dbnames{"contrib_regression_$bad_module"})
+		{
+			_add_st($result, 'postgres',
+				"drop database contrib_regression_$bad_module");
+			delete($dbnames{"contrib_regression_$bad_module"});
+		}
+	}
+
+	# avoid version number issues with test_ext7
+	if ($dbnames{contrib_regression_test_extensions})
+	{
+		_add_st(
+			$result,
+			'contrib_regression_test_extensions',
+			'drop extension if exists test_ext7');
+	}
+
+	# get rid of dblink's dependencies on regress.so
+	my $regrdb =
+	  $old_version le '9.4'
+	  ? 'contrib_regression'
+	  : 'contrib_regression_dblink';
+
+	if ($dbnames{$regrdb})
+	{
+		_add_st(
+			$result, $regrdb,
+			'drop function if exists public.putenv(text)',
+			'drop function if exists public.wait_pid(integer)');
+	}
+
+	return $result;
+}
+
+# Internal subroutine to add statement(s) to the list for the given db.
+sub _add_st
+{
+	my ($result, $db, @st) = @_;
+
+	$result->{$db} ||= [];
+	push(@{ $result->{$db} }, @st);
+}
+
+=pod
+
+=item adjust_old_dumpfile($old_version, $dump)
+
+Edit a dump output file, taken from the adjusted old-version installation
+by current-version C<pg_dumpall -s>, so that it will match the results of
+C<pg_dumpall -s> on the pg_upgrade'd installation.
+
+Typically this involves coping with cosmetic differences in the output
+of backend subroutines used by pg_dump.
+
+Arguments:
+
+=over
+
+=item C<old_version>: Branch we are upgrading from, represented as a
+PostgreSQL::Version object.
+
+=item C<dump>: Contents of dump file
+
+=back
+
+Returns the modified dump text.
+
+=cut
+
+sub adjust_old_dumpfile
+{
+	my ($old_version, $dump) = @_;
+
+	# use Unix newlines
+	$dump =~ s/\r\n/\n/g;
+
+	# Version comments will certainly not match.
+	$dump =~ s/^-- Dumped from database version.*\n//mg;
+
+	if ($old_version lt '9.3')
+	{
+		# CREATE VIEW/RULE statements were not pretty-printed before 9.3.
+		# To cope, reduce all whitespace sequences within them to one space.
+		# This must be done on both old and new dumps.
+		$dump = _mash_view_whitespace($dump);
+
+		# _mash_view_whitespace doesn't handle multi-command rules;
+		# rather than trying to fix that, just hack the exceptions manually.
+
+		my $prefix =
+		  "CREATE RULE rtest_sys_del AS ON DELETE TO public.rtest_system DO (DELETE FROM public.rtest_interface WHERE (rtest_interface.sysname = old.sysname);";
+		my $line2 = " DELETE FROM public.rtest_admin";
+		my $line3 = " WHERE (rtest_admin.sysname = old.sysname);";
+		$dump =~
+		  s/(?<=\Q$prefix\E)\Q$line2$line3\E \);/\n$line2\n $line3\n);/mg;
+
+		$prefix =
+		  "CREATE RULE rtest_sys_upd AS ON UPDATE TO public.rtest_system DO (UPDATE public.rtest_interface SET sysname = new.sysname WHERE (rtest_interface.sysname = old.sysname);";
+		$line2 = " UPDATE public.rtest_admin SET sysname = new.sysname";
+		$line3 = " WHERE (rtest_admin.sysname = old.sysname);";
+		$dump =~
+		  s/(?<=\Q$prefix\E)\Q$line2$line3\E \);/\n$line2\n $line3\n);/mg;
+
+		# and there's one place where pre-9.3 uses a different table alias
+		$dump =~ s {^(CREATE\sRULE\srule_and_refint_t3_ins\sAS\s
+			 ON\sINSERT\sTO\spublic\.rule_and_refint_t3\s
+			 WHERE\s\(EXISTS\s\(SELECT\s1\sFROM\spublic\.rule_and_refint_t3)\s
+			 (WHERE\s\(\(\(rule_and_refint_t3)
+			 (\.id3a\s=\snew\.id3a\)\sAND\s\(rule_and_refint_t3)
+			 (\.id3b\s=\snew\.id3b\)\)\sAND\s\(rule_and_refint_t3)}
+		{$1 rule_and_refint_t3_1 $2_1$3_1$4_1}mx;
+
+		# Also fix old use of NATURAL JOIN syntax
+		$dump =~ s {NATURAL JOIN public\.credit_card r}
+			{JOIN public.credit_card r USING (cid)}mg;
+		$dump =~ s {NATURAL JOIN public\.credit_usage r}
+			{JOIN public.credit_usage r USING (cid)}mg;
+	}
+
+	# Suppress blank lines, as some places in pg_dump emit more or fewer.
+	$dump =~ s/\n\n+/\n/g;
+
+	return $dump;
+}
+
+# Internal subroutine to mangle whitespace within view/rule commands.
+# Any consecutive sequence of whitespace is reduced to one space.
+sub _mash_view_whitespace
+{
+	my ($dump) = @_;
+
+	foreach my $leader ('CREATE VIEW', 'CREATE RULE')
+	{
+		my @splitchunks = split $leader, $dump;
+
+		$dump = shift(@splitchunks);
+		foreach my $chunk (@splitchunks)
+		{
+			my @thischunks = split /;/, $chunk, 2;
+			my $stmt = shift(@thischunks);
+
+			# now $stmt is just the body of the CREATE VIEW/RULE
+			$stmt =~ s/\s+/ /sg;
+			# we also need to smash these forms for sub-selects and rules
+			$stmt =~ s/\( SELECT/(SELECT/g;
+			$stmt =~ s/\( INSERT/(INSERT/g;
+			$stmt =~ s/\( UPDATE/(UPDATE/g;
+			$stmt =~ s/\( DELETE/(DELETE/g;
+
+			$dump .= $leader . $stmt . ';' . $thischunks[0];
+		}
+	}
+	return $dump;
+}
+
+=pod
+
+=item adjust_new_dumpfile($old_version, $dump)
+
+Edit a dump output file, taken from the pg_upgrade'd installation
+by current-version C<pg_dumpall -s>, so that it will match the old
+dump output file as adjusted by C<adjust_old_dumpfile>.
+
+Typically this involves deleting data not present in the old installation.
+
+Arguments:
+
+=over
+
+=item C<old_version>: Branch we are upgrading from, represented as a
+PostgreSQL::Version object.
+
+=item C<dump>: Contents of dump file
+
+=back
+
+Returns the modified dump text.
+
+=cut
+
+sub adjust_new_dumpfile
+{
+	my ($old_version, $dump) = @_;
+
+	# use Unix newlines
+	$dump =~ s/\r\n/\n/g;
+
+	# Version comments will certainly not match.
+	$dump =~ s/^-- Dumped from database version.*\n//mg;
+
+	if ($old_version lt '9.3')
+	{
+		# CREATE VIEW/RULE statements were not pretty-printed before 9.3.
+		# To cope, reduce all whitespace sequences within them to one space.
+		# This must be done on both old and new dumps.
+		$dump = _mash_view_whitespace($dump);
+	}
+
+	# Suppress blank lines, as some places in pg_dump emit more or fewer.
+	$dump =~ s/\n\n+/\n/g;
+
+	return $dump;
+}
+
+=pod
+
+=back
+
+=cut
+
+1;

src/test/perl/PostgreSQL/Version.pm

@@ -0,0 +1,167 @@
+############################################################################
+#
+# PostgreSQL/Version.pm
+#
+# Module encapsulating Postgres Version numbers
+#
+# Copyright (c) 2021-2022, PostgreSQL Global Development Group
+#
+############################################################################
+
+=pod
+
+=head1 NAME
+
+PostgreSQL::Version - class representing PostgreSQL version numbers
+
+=head1 SYNOPSIS
+
+  use PostgreSQL::Version;
+
+  my $version = PostgreSQL::Version->new($version_arg);
+
+  # compare two versions
+  my $bool = $version1 <= $version2;
+
+  # or compare with a number
+  $bool = $version < 12;
+
+  # or with a string
+  $bool = $version lt "13.1";
+
+  # interpolate in a string
+  my $stringyval = "version: $version";
+
+  # get the major version
+  my $maj = $version->major;
+
+=head1 DESCRIPTION
+
+PostgreSQL::Version encapsulates Postgres version numbers, providing parsing
+of common version formats and comparison operations.
+
+=cut
+
+package PostgreSQL::Version;
+
+use strict;
+use warnings;
+
+use Scalar::Util qw(blessed);
+
+use overload
+  '<=>' => \&_version_cmp,
+  'cmp' => \&_version_cmp,
+  '""'  => \&_stringify;
+
+=pod
+
+=head1 METHODS
+
+=over
+
+=item PostgreSQL::Version->new($version)
+
+Create a new PostgreSQL::Version instance.
+
+The argument can be a number like 12, or a string like '12.2' or the output
+of a Postgres command like `psql --version` or `pg_config --version`;
+
+=back
+
+=cut
+
+sub new
+{
+	my $class = shift;
+	my $arg   = shift;
+
+	chomp $arg;
+
+	# Accept standard formats, in case caller has handed us the output of a
+	# postgres command line tool
+	my $devel;
+	($arg, $devel) = ($1, $2)
+	  if (
+		$arg =~ m!^                             # beginning of line
+          (?:\(?PostgreSQL\)?\s)?         # ignore PostgreSQL marker
+          (\d+(?:\.\d+)*)                 # version number, dotted notation
+          (devel|(?:alpha|beta|rc)\d+)?   # dev marker - see version_stamp.pl
+		 !x);
+
+	# Split into an array
+	my @numbers = split(/\./, $arg);
+
+	# Treat development versions as having a minor/micro version one less than
+	# the first released version of that branch.
+	push @numbers, -1 if ($devel);
+
+	$devel ||= "";
+
+	return bless { str => "$arg$devel", num => \@numbers }, $class;
+}
+
+# Routine which compares the _pg_version_array obtained for the two
+# arguments and returns -1, 0, or 1, allowing comparison between two
+# PostgreSQL::Version objects or a PostgreSQL::Version and a version string or number.
+#
+# If the second argument is not a blessed object we call the constructor
+# to make one.
+#
+# Because we're overloading '<=>' and 'cmp' this function supplies us with
+# all the comparison operators ('<' and friends, 'gt' and friends)
+#
+sub _version_cmp
+{
+	my ($a, $b, $swapped) = @_;
+
+	$b = __PACKAGE__->new($b) unless blessed($b);
+
+	($a, $b) = ($b, $a) if $swapped;
+
+	my ($an, $bn) = ($a->{num}, $b->{num});
+
+	for (my $idx = 0;; $idx++)
+	{
+		return 0
+		  if ($idx >= @$an && $idx >= @$bn);
+		# treat a missing number as 0
+		my ($anum, $bnum) = ($an->[$idx] || 0, $bn->[$idx] || 0);
+		return $anum <=> $bnum
+		  if ($anum <=> $bnum);
+	}
+}
+
+# Render the version number using the saved string.
+sub _stringify
+{
+	my $self = shift;
+	return $self->{str};
+}
+
+=pod
+
+=over
+
+=item major([separator => 'char'])
+
+Returns the major version. For versions before 10 the parts are separated by
+a dot unless the separator argument is given.
+
+=back
+
+=cut
+
+sub major
+{
+	my ($self, %params) = @_;
+	my $result = $self->{num}->[0];
+	if ($result + 0 < 10)
+	{
+		my $sep = $params{separator} || '.';
+		$result .= "$sep$self->{num}->[1]";
+	}
+	return $result;
+}
+
+1;