Re: Extracting cross-version-upgrade knowledge from buildfarm client

I wrote:
> OK, I'll take a look at that and make a new draft.

Here's version 2, incorporating your suggestions and with some
further work to make it handle 9.2 fully.  I think this could
be committable so far as HEAD is concerned, though I still
need to make versions of AdjustUpgrade.pm for the back branches.

I tried to use this to replace upgrade_adapt.sql, but failed so
far because I couldn't figure out exactly how you're supposed
to use 002_pg_upgrade.pl with an old source installation.
It's not terribly well documented.  In any case I think we
need a bit more thought about that, because it looks like
002_pg_upgrade.pl thinks that you can supply any random dump
file to serve as the initial state of the old installation;
but neither what I have here nor any likely contents of
upgrade_adapt.sql or the "custom filter" rules are going to
work on databases that aren't just the standard regression
database(s) of the old version.

I assume we should plan on reverting 9814ff550 (Add custom filtering
rules to the TAP tests of pg_upgrade)?  Does that have any
plausible use that's not superseded by this patchset?

            regards, tom lane

diff --git a/src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm b/src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm
new file mode 100644
index 0000000000..622f649b05
--- /dev/null
+++ b/src/test/perl/PostgreSQL/Test/AdjustUpgrade.pm
@@ -0,0 +1,500 @@
+
+# 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.  This can be a branch
+name such as 'HEAD' or 'REL_11_STABLE', but it can also be any string
+that PostgreSQL::Version accepts.
+
+=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 = {};
+
+    # nothing to do for non-cross-version tests
+    return $result if $old_version eq 'HEAD';
+
+    # convert branch name to numeric form
+    $old_version =~ s/REL_?(\d+(?:_\d+)?)_STABLE/$1/;
+    $old_version =~ s/_/./;
+    $old_version = PostgreSQL::Version->new($old_version);
+
+    # 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(
+            $result,
+            'contrib_regression_test_extensions',
+            'drop extension if exists test_ext7');
+    }
+
+    # stuff not supported from release 16
+    if ($old_version >= 12 && $old_version < 16)
+    {
+        # Can't upgrade aclitem in user tables from pre 16 to 16+.
+        _add_st($result, 'regression',
+            'alter table public.tab_core_types drop column aclitem');
+        # Can't handle child tables with locally-generated columns.
+        _add_st(
+            $result, 'regression',
+            'drop table public.gtest_normal_child',
+            'drop table public.gtest_normal_child2');
+    }
+
+    # stuff not supported from release 14
+    if ($old_version < 14)
+    {
+        # postfix operators (some don't exist in very old versions)
+        _add_st(
+            $result,
+            'regression',
+            'drop operator #@# (bigint,NONE)',
+            'drop operator #%# (bigint,NONE)',
+            'drop operator if exists !=- (bigint,NONE)',
+            'drop operator if exists #@%# (bigint,NONE)');
+
+        # 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, $regrdb,
+                'drop function if exists public.putenv(text)',
+                'drop function if exists public.wait_pid(integer)');
+        }
+    }
+
+    # user table OIDs are gone from release 12 on
+    if ($old_version < 12)
+    {
+        my $nooid_stmt = q{
+           DO $stmt$
+           DECLARE
+              rec text;
+           BEGIN
+              FOR rec in
+                 select oid::regclass::text
+                 from pg_class
+                 where relname !~ '^pg_'
+                    and relhasoids
+                    and relkind in ('r','m')
+                 order by 1
+              LOOP
+                 execute 'ALTER TABLE ' || rec || ' SET WITHOUT OIDS';
+                 RAISE NOTICE 'removing oids from table %', rec;
+              END LOOP;
+           END; $stmt$;
+        };
+
+        foreach my $oiddb ('regression', 'contrib_regression_btree_gist')
+        {
+            next unless $dbnames{$oiddb};
+            _add_st($result, $oiddb, $nooid_stmt);
+        }
+
+        # this table had OIDs too, but we'll just drop it
+        if ($old_version >= 10 && $dbnames{'contrib_regression_postgres_fdw'})
+        {
+            _add_st(
+                $result,
+                'contrib_regression_postgres_fdw',
+                'drop foreign table ft_pg_type');
+        }
+    }
+
+    # abstime+friends are gone from release 12 on; but these tables
+    # might or might not be present depending on regression test vintage
+    if ($old_version < 12)
+    {
+        _add_st($result, 'regression',
+            'drop table if exists abstime_tbl, reltime_tbl, tinterval_tbl');
+    }
+
+    # some regression functions gone from release 11 on
+    if ($old_version < 11)
+    {
+        _add_st(
+            $result, 'regression',
+            'drop function if exists public.boxarea(box)',
+            'drop function if exists public.funny_dup17()');
+    }
+
+    # version-0 C functions are no longer supported
+    if ($old_version < 10)
+    {
+        _add_st($result, 'regression',
+            'drop function oldstyle_length(integer, text)');
+    }
+
+    if ($old_version lt '9.5')
+    {
+        # cope with changes of underlying functions
+        _add_st(
+            $result,
+            'regression',
+            'drop operator @#@ (NONE, bigint)',
+            'CREATE OPERATOR @#@ ('
+              . 'PROCEDURE = factorial, RIGHTARG = bigint )',
+            'drop aggregate public.array_cat_accum(anyarray)',
+            'CREATE AGGREGATE array_larger_accum (anyarray) ' . ' ( '
+              . '   sfunc = array_larger, '
+              . '   stype = anyarray, '
+              . '   initcond = $${}$$ ' . '  ) ');
+
+        # "=>" is no longer valid as an operator name
+        _add_st($result, 'regression',
+            'drop operator if exists public.=> (bigint, NONE)');
+    }
+
+    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, $dump)
+
+Edit a dump output file, taken from the adjusted old-version installation
+by current-version C<pg_dumpall -s>, so that it will match the results of
+C<pg_dumpall -s> on the pg_upgrade'd installation.
+
+Typically this involves coping with cosmetic differences in the output
+of backend subroutines used by pg_dump.
+
+Arguments:
+
+=over
+
+=item C<old_version>: Branch we are upgrading from.  This can be a branch
+name such as 'HEAD' or 'REL_11_STABLE', but it can also be any string
+that PostgreSQL::Version accepts.
+
+=item C<dump>: Contents of dump file
+
+=back
+
+Returns the modified dump text.
+
+=cut
+
+sub adjust_old_dumpfile
+{
+    my ($old_version, $dump) = @_;
+
+    # nothing to do for non-cross-version tests
+    return $dump if $old_version eq 'HEAD';
+
+    # convert branch name to numeric form
+    $old_version =~ s/REL_?(\d+(?:_\d+)?)_STABLE/$1/;
+    $old_version =~ s/_/./;
+    $old_version = PostgreSQL::Version->new($old_version);
+
+    # Version comments will certainly not match.
+    $dump =~ s/^-- Dumped from database version.*\n//mg;
+
+    if ($old_version >= 14 && $old_version < 16)
+    {
+        # Fix up some privilege-set discrepancies.
+        $dump =~
+          s/^REVOKE SELECT,INSERT,REFERENCES,DELETE,TRIGGER,TRUNCATE,UPDATE ON TABLE/REVOKE ALL ON TABLE/mg;
+        $dump =~
+          s/^GRANT SELECT,INSERT,REFERENCES,TRIGGER,TRUNCATE,UPDATE ON TABLE/GRANT
SELECT,INSERT,REFERENCES,TRIGGER,TRUNCATE,MAINTAIN,UPDATEON TABLE/mg; 
+    }
+
+    if ($old_version < 14)
+    {
+        # Remove mentions of extended hash functions.
+        $dump =~
+          s/^(\s+OPERATOR 1 =\(integer,integer\)) ,\n\s+FUNCTION 2 \(integer, integer\)
public\.part_hashint4_noop\(integer,bigint\);/$1;/mg;
+        $dump =~
+          s/^(\s+OPERATOR 1 =\(text,text\)) ,\n\s+FUNCTION 2 \(text, text\)
public\.part_hashtext_length\(text,bigint\);/$1;/mg;
+    }
+
+    # Change trigger definitions to say ... EXECUTE FUNCTION ...
+    if ($old_version < 12)
+    {
+        # would like to use lookbehind here but perl complains
+        # so do it this way
+        $dump =~ s/
+            (^CREATE\sTRIGGER\s.*?)
+            \sEXECUTE\sPROCEDURE
+            /$1 EXECUTE FUNCTION/mgx;
+    }
+
+    if ($old_version lt '9.6')
+    {
+        # adjust some places where we don't print so many parens anymore
+        $dump =~
+          s/^'New York'\tnew & york \| big & apple \| nyc\t'new' & 'york'\t\( 'new' & 'york' \| 'big' & 'appl' \) \|
'nyc'/'NewYork'\tnew & york | big & apple | nyc\t'new' & 'york'\t'new' & 'york' | 'big' & 'appl' | 'nyc'/mg; 
+        $dump =~
+          s/^'Sanct Peter'\tPeterburg \| peter \| 'Sanct Peterburg'\t'sanct' & 'peter'\t\( 'peterburg' \| 'peter' \)
\|'sanct' & 'peterburg'/'Sanct Peter'\tPeterburg | peter | 'Sanct Peterburg'\t'sanct' & 'peter'\t'peterburg' | 'peter'
|'sanct' & 'peterburg'/mg; 
+    }
+
+    if ($old_version lt '9.5')
+    {
+        # adjust some places where we don't print so many parens anymore
+        $dump =~
+          s/CONSTRAINT sequence_con CHECK \(\(\(\(x > 3\) AND \(y <> 'check failed'::text\)\) AND \(z <
8\)\)\)/CONSTRAINTsequence_con CHECK (((x > 3) AND (y <> 'check failed'::text) AND (z < 8)))/mg; 
+        $dump =~
+          s/CONSTRAINT copy_con CHECK \(\(\(\(x > 3\) AND \(y <> 'check failed'::text\)\) AND \(x < 7\)\)\)/CONSTRAINT
copy_conCHECK (((x > 3) AND (y <> 'check failed'::text) AND (x < 7)))/mg; 
+        $dump =~
+          s/CONSTRAINT insert_con CHECK \(\(\(\(x >= 3\) AND \(y <> 'check failed'::text\)\) AND \(x <
8\)\)\)/CONSTRAINTinsert_con CHECK (((x >= 3) AND (y <> 'check failed'::text) AND (x < 8)))/mg; 
+        $dump =~
+          s/DEFAULT \(\(-1\) \* currval\('public\.insert_seq'::regclass\)\)/DEFAULT ('-1'::integer *
currval('public.insert_seq'::regclass))/mg;
+        $dump =~
+          s/WHERE \(\(\(rsl\.sl_color = rsh\.slcolor\) AND \(rsl\.sl_len_cm >= rsh\.slminlen_cm\)\) AND
\(rsl\.sl_len_cm<= rsh\.slmaxlen_cm\)\)/WHERE ((rsl.sl_color = rsh.slcolor) AND (rsl.sl_len_cm >= rsh.slminlen_cm) AND
(rsl.sl_len_cm<= rsh.slmaxlen_cm))/mg; 
+        $dump =~
+          s/WHERE \(\(\(rule_and_refint_t3\.id3a = new\.id3a\) AND \(rule_and_refint_t3\.id3b = new\.id3b\)\) AND
\(rule_and_refint_t3\.id3c= new\.id3c\)\)/WHERE ((rule_and_refint_t3.id3a = new.id3a) AND (rule_and_refint_t3.id3b =
new.id3b)AND (rule_and_refint_t3.id3c = new.id3c))/mg; 
+        $dump =~
+          s/WHERE \(\(\(rule_and_refint_t3_1\.id3a = new\.id3a\) AND \(rule_and_refint_t3_1\.id3b = new\.id3b\)\) AND
\(rule_and_refint_t3_1\.id3c= new\.id3c\)\)/WHERE ((rule_and_refint_t3_1.id3a = new.id3a) AND
(rule_and_refint_t3_1.id3b= new.id3b) AND (rule_and_refint_t3_1.id3c = new.id3c))/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.
+        $dump =~
+          s/CREATE RULE rtest_sys_del AS ON DELETE TO public\.rtest_system DO \(DELETE FROM public\.rtest_interface
WHERE\(rtest_interface\.sysname = old\.sysname\); DELETE FROM public\.rtest_admin WHERE \(rtest_admin\.sysname =
old\.sysname\);\);/CREATE RULE rtest_sys_del AS ON DELETE TO public.rtest_system DO (DELETE FROM public.rtest_interface
WHERE(rtest_interface.sysname = old.sysname);\n DELETE FROM public.rtest_admin\n  WHERE (rtest_admin.sysname =
old.sysname);\n);/m;
+        $dump =~
+          s/CREATE RULE rtest_sys_upd AS ON UPDATE TO public\.rtest_system DO \(UPDATE public\.rtest_interface SET
sysname= new\.sysname WHERE \(rtest_interface\.sysname = old\.sysname\); UPDATE public\.rtest_admin SET sysname =
new\.sysnameWHERE \(rtest_admin\.sysname = old\.sysname\); \);/CREATE RULE rtest_sys_upd AS ON UPDATE TO
public.rtest_systemDO (UPDATE public.rtest_interface SET sysname = new.sysname WHERE (rtest_interface.sysname =
old.sysname);\nUPDATE public.rtest_admin SET sysname = new.sysname\n  WHERE (rtest_admin.sysname = old.sysname);\n);/m; 
+
+        # and there's one place where pre-9.3 uses more aliases than we do now
+        $dump =~
+          s/CREATE RULE rule_and_refint_t3_ins AS ON INSERT TO public\.rule_and_refint_t3 WHERE \(EXISTS \(SELECT 1
FROMpublic\.rule_and_refint_t3 WHERE \(\(rule_and_refint_t3\.id3a = new\.id3a\) AND \(rule_and_refint_t3\.id3b =
new\.id3b\)AND \(rule_and_refint_t3\.id3c = new\.id3c\)\)\)\) DO INSTEAD UPDATE public\.rule_and_refint_t3 SET data =
new\.dataWHERE \(\(rule_and_refint_t3\.id3a = new\.id3a\) AND \(rule_and_refint_t3\.id3b = new\.id3b\) AND
\(rule_and_refint_t3\.id3c= new\.id3c\)\);/CREATE RULE rule_and_refint_t3_ins AS ON INSERT TO public.rule_and_refint_t3
WHERE(EXISTS (SELECT 1 FROM public.rule_and_refint_t3 rule_and_refint_t3_1 WHERE ((rule_and_refint_t3_1.id3a =
new.id3a)AND (rule_and_refint_t3_1.id3b = new.id3b) AND (rule_and_refint_t3_1.id3c = new.id3c)))) DO INSTEAD UPDATE
public.rule_and_refint_t3SET data = new.data WHERE ((rule_and_refint_t3.id3a = new.id3a) AND (rule_and_refint_t3.id3b =
new.id3b)AND (rule_and_refint_t3.id3c = new.id3c));/m; 
+
+        # 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, $dump)
+
+Edit a dump output file, taken from the pg_upgrade'd installation
+by current-version C<pg_dumpall -s>, so that it will match the old
+dump output file as adjusted by C<adjust_old_dumpfile>.
+
+Typically this involves deleting data not present in the old installation.
+
+Arguments:
+
+=over
+
+=item C<old_version>: Branch we are upgrading from.  This can be a branch
+name such as 'HEAD' or 'REL_11_STABLE', but it can also be any string
+that PostgreSQL::Version accepts.
+
+=item C<dump>: Contents of dump file
+
+=back
+
+Returns the modified dump text.
+
+=cut
+
+sub adjust_new_dumpfile
+{
+    my ($old_version, $dump) = @_;
+
+    # nothing to do for non-cross-version tests
+    return $dump if $old_version eq 'HEAD';
+
+    # convert branch name to numeric form
+    $old_version =~ s/REL_?(\d+(?:_\d+)?)_STABLE/$1/;
+    $old_version =~ s/_/./;
+    $old_version = PostgreSQL::Version->new($old_version);
+
+    # Version comments will certainly not match.
+    $dump =~ s/^-- Dumped from database version.*\n//mg;
+
+    if ($old_version < 14)
+    {
+        # Suppress noise-word uses of IN in CREATE/ALTER PROCEDURE.
+        $dump =~ s/^(CREATE PROCEDURE .*?)\(IN /$1(/mg;
+        $dump =~ s/^(ALTER PROCEDURE .*?)\(IN /$1(/mg;
+        $dump =~ s/^(CREATE PROCEDURE .*?), IN /$1, /mg;
+        $dump =~ s/^(ALTER PROCEDURE .*?), IN /$1, /mg;
+        $dump =~ s/^(CREATE PROCEDURE .*?), IN /$1, /mg;
+        $dump =~ s/^(ALTER PROCEDURE .*?), IN /$1, /mg;
+
+        # Remove SUBSCRIPT clauses in CREATE TYPE.
+        $dump =~ s/^\s+SUBSCRIPT = raw_array_subscript_handler,\n//mg;
+
+        # Remove multirange_type_name clauses in CREATE TYPE AS RANGE.
+        $dump =~ s/,\n\s+multirange_type_name = .*?(,?)$/$1/mg;
+
+        # Remove mentions of extended hash functions.
+        $dump =~
+          s/^ALTER OPERATOR FAMILY public\.part_test_int4_ops USING hash ADD\n\s+FUNCTION 2 \(integer, integer\)
public\.part_hashint4_noop\(integer,bigint\);//mg;
+        $dump =~
+          s/^ALTER OPERATOR FAMILY public\.part_test_text_ops USING hash ADD\n\s+FUNCTION 2 \(text, text\)
public\.part_hashtext_length\(text,bigint\);//mg;
+    }
+
+    # pre-v12 dumps will not say anything about default_table_access_method.
+    if ($old_version < 12)
+    {
+        $dump =~ s/^SET default_table_access_method = heap;\n//mg;
+    }
+
+    # dumps from pre-9.6 dblink may include redundant ACL settings
+    if ($old_version lt '9.6')
+    {
+        $dump =~
+          s/^--\n-- Name: FUNCTION dblink_connect_u\(text\); Type: ACL; Schema: public; Owner: .*\n--\n+REVOKE ALL ON
FUNCTIONpublic\.dblink_connect_u\(text\) FROM PUBLIC;\n+--\n-- Name: FUNCTION dblink_connect_u\(text, text\); Type:
ACL;Schema: public; Owner: .*\n--\n+REVOKE ALL ON FUNCTION public\.dblink_connect_u\(text, text\) FROM PUBLIC;\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;
diff -pudr client-code-REL_16.orig/PGBuild/Modules/TestUpgradeXversion.pm
client-code-REL_16/PGBuild/Modules/TestUpgradeXversion.pm
--- client-code-REL_16.orig/PGBuild/Modules/TestUpgradeXversion.pm    2023-01-13 12:20:51.000000000 -0500
+++ client-code-REL_16/PGBuild/Modules/TestUpgradeXversion.pm    2023-01-14 14:23:27.120834037 -0500
@@ -323,31 +323,6 @@ sub save_for_testing
         return if $?;
     }

-    if ($this_branch ne 'HEAD' && $this_branch le 'REL9_4_STABLE')
-    {
-        my $opsql = 'drop operator if exists public.=> (bigint, NONE)';
-
-        # syntax is illegal in 9.5 and later, and it shouldn't
-        # be possible for it to exist there anyway.
-        # quoting the operator can also fail,  so it's left unquoted.
-        run_psql("$installdir/bin/psql", "-e", $opsql, "regression",
-            "$upgrade_loc/fix.log", 1);
-        return if $?;
-    }
-
-    # remove dbs of modules known to cause pg_upgrade to fail
-    # anything not builtin and incompatible should clean up its own db
-    # e.g. jsonb_set_lax
-
-    foreach my $bad_module ("test_ddl_deparse")
-    {
-        my $dsql = "drop database if exists contrib_regression_$bad_module";
-
-        run_psql("$installdir/bin/psql", "-e", $dsql,
-            "postgres", "$upgrade_loc/fix.log", 1);
-        return if $?;
-    }
-
     # use a different logfile here to get around windows sharing issue
     system( qq{"$installdir/bin/pg_ctl" -D "$installdir/data-C" -w stop }
           . qq{>> "$upgrade_loc/ctl2.log" 2>&1});
@@ -375,6 +350,12 @@ sub test_upgrade    ## no critic (Subrou
     print time_str(), "checking upgrade from $oversion to $this_branch ...\n"
       if $verbose;

+    # load helper module from source tree
+    unshift(@INC, "$self->{pgsql}/src/test/perl");
+    require PostgreSQL::Test::AdjustUpgrade;
+    PostgreSQL::Test::AdjustUpgrade->import;
+    shift(@INC);
+
     rmtree "$other_branch/inst/$upgrade_test";
     copydir(
         "$other_branch/inst/data-C",
@@ -414,6 +395,7 @@ sub test_upgrade    ## no critic (Subrou

     return if $?;

+    # collect names of databases present in old installation.
     my $sql = 'select datname from pg_database';

     run_psql("psql", "-A -t", $sql, "postgres",
@@ -425,186 +407,19 @@ sub test_upgrade    ## no critic (Subrou
     do { s/\r$//; $dbnames{$_} = 1; }
       foreach @dbnames;

-    if ($this_branch gt 'REL9_6_STABLE' || $this_branch eq 'HEAD')
-    {
-        run_psql(
-            "$other_branch/inst/bin/psql",                         "-e",
-            "drop database if exists contrib_regression_tsearch2", "postgres",
-            "$upgrade_loc/$oversion-copy.log",                     1
-        );
-        return if $?;
-
-        run_psql(
-            "$other_branch/inst/bin/psql",
-            "-e",
-            "drop function if exists oldstyle_length(integer, text)",
-            "regression",
-            "$upgrade_loc/$oversion-copy.log",
-            1
-        );
-        return if $?;
-    }
-
-    # some regression functions gone from release 11 on
-    if (   ($this_branch ge 'REL_11_STABLE' || $this_branch eq 'HEAD')
-        && ($oversion lt 'REL_11_STABLE' && $oversion ne 'HEAD'))
-    {
-        my $missing_funcs = q{drop function if exists public.boxarea(box);
-                              drop function if exists public.funny_dup17();
-                            };
-        $missing_funcs =~ s/\n//g;
-
-        run_psql("$other_branch/inst/bin/psql", "-e", $missing_funcs,
-            "regression", "$upgrade_loc/$oversion-copy.log", 1);
-        return if $?;
-    }
-
-    # avoid version number issues with test_ext7
-    if ($dbnames{contrib_regression_test_extensions})
-    {
-        my $noext7 = "drop extension if exists test_ext7";
-        run_psql(
-            "$other_branch/inst/bin/psql", "-e", $noext7,
-            "contrib_regression_test_extensions",
-            "$upgrade_loc/$oversion-copy.log", 1
-        );
-        return if $?;
-    }
-
-    # user table OIDS and abstime+friends are gone from release 12 on
-    if (   ($this_branch gt 'REL_11_STABLE' || $this_branch eq 'HEAD')
-        && ($oversion le 'REL_11_STABLE' && $oversion ne 'HEAD'))
-    {
-        my $nooid_stmt = q{
-           DO $stmt$
-           DECLARE
-              rec text;
-           BEGIN
-              FOR rec in
-                 select oid::regclass::text
-                 from pg_class
-                 where relname !~ '^pg_'
-                    and relhasoids
-                    and relkind in ('r','m')
-                 order by 1
-              LOOP
-                 execute 'ALTER TABLE ' || rec || ' SET WITHOUT OIDS';
-                 RAISE NOTICE 'removing oids from table %', rec;
-              END LOOP;
-           END; $stmt$;
-        };
-        foreach my $oiddb ("regression", "contrib_regression_btree_gist")
-        {
-            next unless $dbnames{$oiddb};
-            run_psql("$other_branch/inst/bin/psql", "-e", $nooid_stmt,
-                "$oiddb", "$upgrade_loc/$oversion-copy.log", 1);
-            return if $?;
-        }
-
-        if (   $oversion ge 'REL_10_STABLE'
-            && $dbnames{'contrib_regression_postgres_fdw'})
-        {
-            run_psql(
-                "$other_branch/inst/bin/psql",
-                "-e",
-                "drop foreign table if exists ft_pg_type",
-                "contrib_regression_postgres_fdw",
-                "$upgrade_loc/$oversion-copy.log",
-                1
-            );
-            return if $?;
-        }
-
-        if ($oversion lt 'REL9_3_STABLE')
-        {
-            run_psql(
-                "$other_branch/inst/bin/psql",
-                "-e",
-                "drop table if exists abstime_tbl, reltime_tbl, tinterval_tbl",
-                "regression",
-                "$upgrade_loc/$oversion-copy.log",
-                1
-            );
-            return if $?;
-        }
-    }
-
-    # stuff not supported from release 14
-    if (   ($this_branch gt 'REL_13_STABLE' || $this_branch eq 'HEAD')
-        && ($oversion le 'REL_13_STABLE' && $oversion ne 'HEAD'))
-    {
-        my $prstmt = join(';',
-            'drop operator if exists #@# (bigint,NONE)',
-            'drop operator if exists #%# (bigint,NONE)',
-            'drop operator if exists !=- (bigint,NONE)',
-            'drop operator if exists #@%# (bigint,NONE)');
-
-        run_psql("$other_branch/inst/bin/psql", "-e", $prstmt,
-            "regression", "$upgrade_loc/$oversion-copy.log", 1);
-        return if $?;
-
-        $prstmt = "drop function if exists public.putenv(text)";
-
-        my $regrdb =
-          $oversion le "REL9_4_STABLE"
-          ? "contrib_regression"
-          : "contrib_regression_dblink";
-
-        if ($dbnames{$regrdb})
-        {
-            run_psql("$other_branch/inst/bin/psql", "-e", $prstmt,
-                "$regrdb", "$upgrade_loc/$oversion-copy.log", 1);
-            return if $?;
-        }
-
-        if ($oversion le 'REL9_4_STABLE')
-        {
-            # this is fixed in 9.5 and later
-            $prstmt = join(';',
-                'drop operator @#@ (NONE, bigint)',
-                'CREATE OPERATOR @#@ ('
-                  . 'PROCEDURE = factorial, '
-                  . 'RIGHTARG = bigint )');
-            run_psql("$other_branch/inst/bin/psql", "-e", $prstmt,
-                "regression", "$upgrade_loc/$oversion-copy.log", 1);
-            return if $?;
-        }
-
-        if ($oversion le 'REL9_4_STABLE')
-        {
-            # this is fixed in 9.5 and later
-            $prstmt = join(';',
-                'drop aggregate if exists public.array_cat_accum(anyarray)',
-                'CREATE AGGREGATE array_larger_accum (anyarray) ' . ' ( '
-                  . '   sfunc = array_larger, '
-                  . '   stype = anyarray, '
-                  . '   initcond = $${}$$ '
-                  . '  ) ');
-            run_psql("$other_branch/inst/bin/psql", "-e", $prstmt,
-                "regression", "$upgrade_loc/$oversion-copy.log", 1);
-            return if $?;
-        }
-    }
+    # obtain and execute commands needed to make old database upgradable.
+    my $adjust_cmds = adjust_database_contents($oversion, %dbnames);

-    # stuff not supported from release 16
-    if (   ($this_branch gt 'REL_15_STABLE' || $this_branch eq 'HEAD')
-        && ($oversion le 'REL_15_STABLE' && $oversion ne 'HEAD'))
+    foreach my $updb (keys %$adjust_cmds)
     {
-        # Can't upgrade aclitem in user tables from pre 16 to 16+.
-        # Also can't handle child tables with newly-generated columns.
-        my $prstmt = join(
-            ';',
-            'alter table if exists public.tab_core_types
-                          drop column if exists aclitem',
-            'drop table if exists public.gtest_normal_child',
-            'drop table if exists public.gtest_normal_child2'
-        );
+        my $upcmds = join(";\n", @{ $adjust_cmds->{$updb} });

-        run_psql("$other_branch/inst/bin/psql", "-e", $prstmt,
-            "regression", "$upgrade_loc/$oversion-copy.log", 1);
+        run_psql("$other_branch/inst/bin/psql", "-e -v ON_ERROR_STOP=1",
+            $upcmds, $updb, "$upgrade_loc/$oversion-fix.log", 1);
         return if $?;
     }

+    # perform a dump from the old database for comparison purposes.
     my $extra_digits = "";

     if (   $oversion ne 'HEAD'
@@ -793,28 +608,27 @@ sub test_upgrade    ## no critic (Subrou
         return if $?;
     }

-    foreach my $dump ("$upgrade_loc/origin-$oversion.sql",
-        "$upgrade_loc/converted-$oversion-to-$this_branch.sql")
-    {
-        # Change trigger definitions to say ... EXECUTE FUNCTION ...
+    my $olddumpfile = "$upgrade_loc/origin-$oversion.sql";
+    my $dump        = file_contents($olddumpfile);

-        my $contents = file_contents($dump);
+    $dump = adjust_old_dumpfile($oversion, $dump);

-        # would like to use lookbehind here but perl complains
-        # so do it this way
-        $contents =~ s/
-                         (^CREATE\sTRIGGER\s.*?)
-                         \sEXECUTE\sPROCEDURE
-                      /$1 EXECUTE FUNCTION/mgx;
-        open(my $dh, '>', "$dump.fixed") || die "opening $dump.fixed";
-        print $dh $contents;
-        close($dh);
-    }
+    open(my $odh, '>', "$olddumpfile.fixed")
+      || die "opening $olddumpfile.fixed: $!";
+    print $odh $dump;
+    close($odh);

-    system( qq{diff -I "^\$" -I "SET default_table_access_method = heap;" }
-          . qq{ -I "^SET default_toast_compression = 'pglz';\$" -I "^-- " }
-          . qq{-u "$upgrade_loc/origin-$oversion.sql.fixed" }
-          . qq{"$upgrade_loc/converted-$oversion-to-$this_branch.sql.fixed" }
+    my $newdumpfile = "$upgrade_loc/converted-$oversion-to-$this_branch.sql";
+    $dump = file_contents($newdumpfile);
+
+    $dump = adjust_new_dumpfile($oversion, $dump);
+
+    open(my $ndh, '>', "$newdumpfile.fixed")
+      || die "opening $newdumpfile.fixed: $!";
+    print $ndh $dump;
+    close($ndh);
+
+    system( qq{diff -u "$olddumpfile.fixed" "$newdumpfile.fixed" }
           . qq{> "$upgrade_loc/dumpdiff-$oversion" 2>&1});

     # diff exits with status 1 if files differ
@@ -829,22 +643,7 @@ sub test_upgrade    ## no critic (Subrou
     }
     close($diffile);

-    # If the versions match we require that there be no diff lines.
-    # In the past we have seen a handful of diffs from reordering of
-    # large object output, but that appears to have disppeared.
-    # If the versions don't match we heuristically allow more lines of diffs
-    # based on observed differences. For versions from 9.6 on, that's
-    # not very many lines, though.
-
-    if (
-        ($oversion eq $this_branch && $difflines == 0)
-        || (   $oversion ne $this_branch
-            && $oversion ge 'REL9_6_STABLE'
-            && $difflines < 90)
-        || (   $oversion ne $this_branch
-            && $oversion lt 'REL9_6_STABLE'
-            && $difflines < 700)
-      )
+    if ($difflines == 0)
     {
         return 1;
     }