Getting rid of "tuple concurrently updated" elog()s with concurrent DDLs (at least ALTER TABLE)

diff --git a/src/test/isolation/expected/concurrent-database.out b/src/test/isolation/expected/concurrent-database.out
new file mode 100644
index 0000000000..59da795117
--- /dev/null
+++ b/src/test/isolation/expected/concurrent-database.out
@@ -0,0 +1,105 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1_begin s1_alterdb_with s2_begin s2_alterdb_with s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterdb_with: 
+	ALTER DATABASE regress_database WITH ALLOW_CONNECTIONS true;
+step s2_begin: BEGIN;
+step s2_alterdb_with: 
+	ALTER DATABASE regress_database WITH ALLOW_CONNECTIONS true; <waiting ...>
+step s1_commit: COMMIT;
+step s2_alterdb_with: <... completed>
+error in steps s1_commit s2_alterdb_with: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterdb_with s2_begin s2_alterdb_set s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterdb_with: 
+	ALTER DATABASE regress_database WITH ALLOW_CONNECTIONS true;
+step s2_begin: BEGIN;
+step s2_alterdb_set: 
+	ALTER DATABASE regress_database SET commit_delay = '10';
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterdb_with s2_begin s2_alterdb_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterdb_with: 
+	ALTER DATABASE regress_database WITH ALLOW_CONNECTIONS true;
+step s2_begin: BEGIN;
+step s2_alterdb_owner: 
+	ALTER DATABASE regress_database OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterdb_with s2_begin s2_alterdb_tbc s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterdb_with: 
+	ALTER DATABASE regress_database WITH ALLOW_CONNECTIONS true;
+step s2_begin: BEGIN;
+step s2_alterdb_tbc: 
+	ALTER DATABASE regress_database SET TABLESPACE TO DEFAULT;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterdb_set s2_begin s2_alterdb_set s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterdb_set: 
+	ALTER DATABASE regress_database SET commit_delay = '10';
+step s2_begin: BEGIN;
+step s2_alterdb_set: 
+	ALTER DATABASE regress_database SET commit_delay = '10'; <waiting ...>
+step s1_commit: COMMIT;
+step s2_alterdb_set: <... completed>
+error in steps s1_commit s2_alterdb_set: ERROR:  duplicate key value violates unique constraint "pg_db_role_setting_databaseid_rol_index"
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterdb_set s2_begin s2_alterdb_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterdb_set: 
+	ALTER DATABASE regress_database SET commit_delay = '10';
+step s2_begin: BEGIN;
+step s2_alterdb_owner: 
+	ALTER DATABASE regress_database OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterdb_set s2_begin s2_alterdb_tbc s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterdb_set: 
+	ALTER DATABASE regress_database SET commit_delay = '10';
+step s2_begin: BEGIN;
+step s2_alterdb_tbc: 
+	ALTER DATABASE regress_database SET TABLESPACE TO DEFAULT;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterdb_owner s2_begin s2_alterdb_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterdb_owner: 
+	ALTER DATABASE regress_database OWNER TO CURRENT_USER;
+step s2_begin: BEGIN;
+step s2_alterdb_owner: 
+	ALTER DATABASE regress_database OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterdb_owner s2_begin s2_alterdb_tbc s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterdb_owner: 
+	ALTER DATABASE regress_database OWNER TO CURRENT_USER;
+step s2_begin: BEGIN;
+step s2_alterdb_tbc: 
+	ALTER DATABASE regress_database SET TABLESPACE TO DEFAULT;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterdb_tbc s2_begin s2_alterdb_tbc s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterdb_tbc: 
+	ALTER DATABASE regress_database SET TABLESPACE TO DEFAULT;
+step s2_begin: BEGIN;
+step s2_alterdb_tbc: 
+	ALTER DATABASE regress_database SET TABLESPACE TO DEFAULT;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
diff --git a/src/test/isolation/expected/concurrent-domain.out b/src/test/isolation/expected/concurrent-domain.out
new file mode 100644
index 0000000000..caf7902d45
--- /dev/null
+++ b/src/test/isolation/expected/concurrent-domain.out
@@ -0,0 +1,519 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1_begin s1_dom_set_notnull s2_begin s2_dom_set_notnull s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_notnull: 
+	ALTER DOMAIN regress_domain_conc SET NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_set_notnull: 
+	ALTER DOMAIN regress_domain_conc SET NOT NULL; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_set_notnull: <... completed>
+error in steps s1_commit s2_dom_set_notnull: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_notnull s2_begin s2_dom_drop_notnull s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_notnull: 
+	ALTER DOMAIN regress_domain_conc SET NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_drop_notnull: 
+	ALTER DOMAIN regress_domain_conc DROP NOT NULL;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_notnull s2_begin s2_dom_set_default s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_notnull: 
+	ALTER DOMAIN regress_domain_conc SET NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_set_default: 
+	ALTER DOMAIN regress_domain_conc SET DEFAULT 1; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_set_default: <... completed>
+error in steps s1_commit s2_dom_set_default: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_notnull s2_begin s2_dom_drop_default s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_notnull: 
+	ALTER DOMAIN regress_domain_conc SET NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_drop_default: 
+	ALTER DOMAIN regress_domain_conc DROP DEFAULT; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_drop_default: <... completed>
+error in steps s1_commit s2_dom_drop_default: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_notnull s2_begin s2_dom_add_con s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_notnull: 
+	ALTER DOMAIN regress_domain_conc SET NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_notnull s2_begin s2_dom_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_notnull: 
+	ALTER DOMAIN regress_domain_conc SET NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_owner: 
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_notnull s2_begin s2_dom_schema_priv s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_notnull: 
+	ALTER DOMAIN regress_domain_conc SET NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_schema_priv: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_schema_priv: <... completed>
+error in steps s1_commit s2_dom_schema_priv: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_notnull s2_begin s2_dom_schema_publ s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_notnull: 
+	ALTER DOMAIN regress_domain_conc SET NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_notnull s2_begin s2_dom_drop_notnull s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_notnull: 
+	ALTER DOMAIN regress_domain_conc DROP NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_drop_notnull: 
+	ALTER DOMAIN regress_domain_conc DROP NOT NULL;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_notnull s2_begin s2_dom_set_default s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_notnull: 
+	ALTER DOMAIN regress_domain_conc DROP NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_set_default: 
+	ALTER DOMAIN regress_domain_conc SET DEFAULT 1;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_notnull s2_begin s2_dom_drop_default s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_notnull: 
+	ALTER DOMAIN regress_domain_conc DROP NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_drop_default: 
+	ALTER DOMAIN regress_domain_conc DROP DEFAULT;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_notnull s2_begin s2_dom_add_con s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_notnull: 
+	ALTER DOMAIN regress_domain_conc DROP NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_notnull s2_begin s2_dom_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_notnull: 
+	ALTER DOMAIN regress_domain_conc DROP NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_owner: 
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_notnull s2_begin s2_dom_schema_priv s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_notnull: 
+	ALTER DOMAIN regress_domain_conc DROP NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_schema_priv: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_notnull s2_begin s2_dom_schema_publ s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_notnull: 
+	ALTER DOMAIN regress_domain_conc DROP NOT NULL;
+step s2_begin: BEGIN;
+step s2_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_default s2_begin s2_dom_set_default s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_default: 
+	ALTER DOMAIN regress_domain_conc SET DEFAULT 1;
+step s2_begin: BEGIN;
+step s2_dom_set_default: 
+	ALTER DOMAIN regress_domain_conc SET DEFAULT 1; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_set_default: <... completed>
+error in steps s1_commit s2_dom_set_default: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_default s2_begin s2_dom_drop_default s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_default: 
+	ALTER DOMAIN regress_domain_conc SET DEFAULT 1;
+step s2_begin: BEGIN;
+step s2_dom_drop_default: 
+	ALTER DOMAIN regress_domain_conc DROP DEFAULT; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_drop_default: <... completed>
+error in steps s1_commit s2_dom_drop_default: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_default s2_begin s2_dom_add_con s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_default: 
+	ALTER DOMAIN regress_domain_conc SET DEFAULT 1;
+step s2_begin: BEGIN;
+step s2_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_default s2_begin s2_dom_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_default: 
+	ALTER DOMAIN regress_domain_conc SET DEFAULT 1;
+step s2_begin: BEGIN;
+step s2_dom_owner: 
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_default s2_begin s2_dom_schema_priv s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_default: 
+	ALTER DOMAIN regress_domain_conc SET DEFAULT 1;
+step s2_begin: BEGIN;
+step s2_dom_schema_priv: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_schema_priv: <... completed>
+error in steps s1_commit s2_dom_schema_priv: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_set_default s2_begin s2_dom_schema_publ s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_set_default: 
+	ALTER DOMAIN regress_domain_conc SET DEFAULT 1;
+step s2_begin: BEGIN;
+step s2_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_default s2_begin s2_dom_drop_default s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_default: 
+	ALTER DOMAIN regress_domain_conc DROP DEFAULT;
+step s2_begin: BEGIN;
+step s2_dom_drop_default: 
+	ALTER DOMAIN regress_domain_conc DROP DEFAULT; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_drop_default: <... completed>
+error in steps s1_commit s2_dom_drop_default: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_default s2_begin s2_dom_add_con s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_default: 
+	ALTER DOMAIN regress_domain_conc DROP DEFAULT;
+step s2_begin: BEGIN;
+step s2_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_default s2_begin s2_dom_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_default: 
+	ALTER DOMAIN regress_domain_conc DROP DEFAULT;
+step s2_begin: BEGIN;
+step s2_dom_owner: 
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_default s2_begin s2_dom_schema_priv s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_default: 
+	ALTER DOMAIN regress_domain_conc DROP DEFAULT;
+step s2_begin: BEGIN;
+step s2_dom_schema_priv: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_schema_priv: <... completed>
+error in steps s1_commit s2_dom_schema_priv: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_drop_default s2_begin s2_dom_schema_publ s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_drop_default: 
+	ALTER DOMAIN regress_domain_conc DROP DEFAULT;
+step s2_begin: BEGIN;
+step s2_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_add_con s2_begin s2_dom_add_con2 s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s2_begin: BEGIN;
+step s2_dom_add_con2: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con2 CHECK (VALUE > 0);
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_add_con s2_begin s2_dom_drop_con s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s2_begin: BEGIN;
+step s2_dom_drop_con: 
+	ALTER DOMAIN regress_domain_conc DROP CONSTRAINT dom_con;
+ERROR:  constraint "dom_con" of domain "regress_domain_conc" does not exist
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_add_con s2_begin s2_dom_validate_con s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s2_begin: BEGIN;
+step s2_dom_validate_con: 
+	ALTER DOMAIN regress_domain_conc VALIDATE CONSTRAINT dom_con;
+ERROR:  constraint "dom_con" of domain "regress_domain_conc" does not exist
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_add_con s2_begin s2_dom_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s2_begin: BEGIN;
+step s2_dom_owner: 
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_add_con s2_begin s2_dom_schema_priv s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s2_begin: BEGIN;
+step s2_dom_schema_priv: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_add_con s2_begin s2_dom_schema_publ s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s2_begin: BEGIN;
+step s2_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_dom_add_con s1_begin s1_dom_drop_con s2_begin s2_dom_drop_con s1_commit s2_commit
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_begin: BEGIN;
+step s1_dom_drop_con: 
+	ALTER DOMAIN regress_domain_conc DROP CONSTRAINT dom_con;
+step s2_begin: BEGIN;
+step s2_dom_drop_con: 
+	ALTER DOMAIN regress_domain_conc DROP CONSTRAINT dom_con; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_drop_con: <... completed>
+error in steps s1_commit s2_dom_drop_con: ERROR:  cache lookup failed for constraint 16509
+step s2_commit: COMMIT;
+
+starting permutation: s1_dom_add_con s1_begin s1_dom_drop_con s2_begin s2_dom_validate_con s1_commit s2_commit
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_begin: BEGIN;
+step s1_dom_drop_con: 
+	ALTER DOMAIN regress_domain_conc DROP CONSTRAINT dom_con;
+step s2_begin: BEGIN;
+step s2_dom_validate_con: 
+	ALTER DOMAIN regress_domain_conc VALIDATE CONSTRAINT dom_con; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_validate_con: <... completed>
+error in steps s1_commit s2_dom_validate_con: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_dom_add_con s1_begin s1_dom_drop_con s2_begin s2_dom_owner s1_commit s2_commit
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_begin: BEGIN;
+step s1_dom_drop_con: 
+	ALTER DOMAIN regress_domain_conc DROP CONSTRAINT dom_con;
+step s2_begin: BEGIN;
+step s2_dom_owner: 
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_dom_add_con s1_begin s1_dom_drop_con s2_begin s2_dom_schema_publ s1_commit s2_commit
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_begin: BEGIN;
+step s1_dom_drop_con: 
+	ALTER DOMAIN regress_domain_conc DROP CONSTRAINT dom_con;
+step s2_begin: BEGIN;
+step s2_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_dom_add_con s1_begin s1_dom_drop_con s2_begin s2_dom_schema_priv s1_commit s2_commit
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_begin: BEGIN;
+step s1_dom_drop_con: 
+	ALTER DOMAIN regress_domain_conc DROP CONSTRAINT dom_con;
+step s2_begin: BEGIN;
+step s2_dom_schema_priv: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_schema_priv: <... completed>
+error in steps s1_commit s2_dom_schema_priv: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_dom_add_con s1_begin s1_dom_validate_con s2_begin s2_dom_validate_con s1_commit s2_commit
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_begin: BEGIN;
+step s1_dom_validate_con: 
+	ALTER DOMAIN regress_domain_conc VALIDATE CONSTRAINT dom_con;
+step s2_begin: BEGIN;
+step s2_dom_validate_con: 
+	ALTER DOMAIN regress_domain_conc VALIDATE CONSTRAINT dom_con; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_validate_con: <... completed>
+error in steps s1_commit s2_dom_validate_con: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_dom_add_con s1_begin s1_dom_validate_con s2_begin s2_dom_owner s1_commit s2_commit
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_begin: BEGIN;
+step s1_dom_validate_con: 
+	ALTER DOMAIN regress_domain_conc VALIDATE CONSTRAINT dom_con;
+step s2_begin: BEGIN;
+step s2_dom_owner: 
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_dom_add_con s1_begin s1_dom_validate_con s2_begin s2_dom_schema_priv s1_commit s2_commit
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_begin: BEGIN;
+step s1_dom_validate_con: 
+	ALTER DOMAIN regress_domain_conc VALIDATE CONSTRAINT dom_con;
+step s2_begin: BEGIN;
+step s2_dom_schema_priv: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema; <waiting ...>
+step s1_commit: COMMIT;
+step s2_dom_schema_priv: <... completed>
+error in steps s1_commit s2_dom_schema_priv: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_dom_add_con s1_begin s1_dom_validate_con s2_begin s2_dom_schema_publ s1_commit s2_commit
+step s1_dom_add_con: 
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0);
+step s1_begin: BEGIN;
+step s1_dom_validate_con: 
+	ALTER DOMAIN regress_domain_conc VALIDATE CONSTRAINT dom_con;
+step s2_begin: BEGIN;
+step s2_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_owner s2_begin s2_dom_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_owner: 
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER;
+step s2_begin: BEGIN;
+step s2_dom_owner: 
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_owner s2_begin s2_dom_schema_priv s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_owner: 
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER;
+step s2_begin: BEGIN;
+step s2_dom_schema_priv: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_owner s2_begin s2_dom_schema_publ s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_owner: 
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER;
+step s2_begin: BEGIN;
+step s2_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_schema_priv s2_begin s2_dom_schema_publ s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_schema_priv: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema;
+step s2_begin: BEGIN;
+step s2_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_schema_publ s2_begin s2_dom_schema_priv s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s2_begin: BEGIN;
+step s2_dom_schema_priv: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_dom_schema_publ s2_begin s2_dom_schema_publ s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s2_begin: BEGIN;
+step s2_dom_schema_publ: 
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
diff --git a/src/test/isolation/expected/concurrent-event-trigger.out b/src/test/isolation/expected/concurrent-event-trigger.out
new file mode 100644
index 0000000000..43dca2d8af
--- /dev/null
+++ b/src/test/isolation/expected/concurrent-event-trigger.out
@@ -0,0 +1,55 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1_begin s1_disable s2_begin s2_disable s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_disable: ALTER EVENT TRIGGER notice_ddl DISABLE;
+step s2_begin: BEGIN;
+step s2_disable: ALTER EVENT TRIGGER notice_ddl DISABLE; <waiting ...>
+step s1_commit: COMMIT;
+step s2_disable: <... completed>
+error in steps s1_commit s2_disable: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_disable s2_begin s2_enable s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_disable: ALTER EVENT TRIGGER notice_ddl DISABLE;
+step s2_begin: BEGIN;
+step s2_enable: ALTER EVENT TRIGGER notice_ddl ENABLE REPLICA; <waiting ...>
+step s1_commit: COMMIT;
+step s2_enable: <... completed>
+error in steps s1_commit s2_enable: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_disable s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_disable: ALTER EVENT TRIGGER notice_ddl DISABLE;
+step s2_begin: BEGIN;
+step s2_owner: ALTER EVENT TRIGGER notice_ddl OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_enable s2_begin s2_enable s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_enable: ALTER EVENT TRIGGER notice_ddl ENABLE REPLICA;
+step s2_begin: BEGIN;
+step s2_enable: ALTER EVENT TRIGGER notice_ddl ENABLE REPLICA; <waiting ...>
+step s1_commit: COMMIT;
+step s2_enable: <... completed>
+error in steps s1_commit s2_enable: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_enable s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_enable: ALTER EVENT TRIGGER notice_ddl ENABLE REPLICA;
+step s2_begin: BEGIN;
+step s2_owner: ALTER EVENT TRIGGER notice_ddl OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_owner s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_owner: ALTER EVENT TRIGGER notice_ddl OWNER TO CURRENT_USER;
+step s2_begin: BEGIN;
+step s2_owner: ALTER EVENT TRIGGER notice_ddl OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
diff --git a/src/test/isolation/expected/concurrent-fdw.out b/src/test/isolation/expected/concurrent-fdw.out
new file mode 100644
index 0000000000..9c3724df34
--- /dev/null
+++ b/src/test/isolation/expected/concurrent-fdw.out
@@ -0,0 +1,118 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1_begin s1_options s2_begin s2_options s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_options: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw OPTIONS (a '1');
+step s2_begin: BEGIN;
+step s2_options: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw OPTIONS (a '1'); <waiting ...>
+step s1_commit: COMMIT;
+step s2_options: <... completed>
+error in steps s1_commit s2_options: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_options s2_begin s2_validator s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_options: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw OPTIONS (a '1');
+step s2_begin: BEGIN;
+step s2_validator: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO VALIDATOR; <waiting ...>
+step s1_commit: COMMIT;
+step s2_validator: <... completed>
+error in steps s1_commit s2_validator: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_options s2_begin s2_handler s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_options: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw OPTIONS (a '1');
+step s2_begin: BEGIN;
+WARNING:  changing the foreign-data wrapper handler can change behavior of existing foreign tables
+step s2_handler: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO HANDLER; <waiting ...>
+step s1_commit: COMMIT;
+step s2_handler: <... completed>
+error in steps s1_commit s2_handler: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_options s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_options: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw OPTIONS (a '1');
+step s2_begin: BEGIN;
+step s2_owner: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_validator s2_begin s2_validator s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_validator: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO VALIDATOR;
+step s2_begin: BEGIN;
+step s2_validator: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO VALIDATOR; <waiting ...>
+step s1_commit: COMMIT;
+step s2_validator: <... completed>
+error in steps s1_commit s2_validator: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_validator s2_begin s2_handler s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_validator: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO VALIDATOR;
+step s2_begin: BEGIN;
+WARNING:  changing the foreign-data wrapper handler can change behavior of existing foreign tables
+step s2_handler: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO HANDLER; <waiting ...>
+step s1_commit: COMMIT;
+step s2_handler: <... completed>
+error in steps s1_commit s2_handler: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_validator s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_validator: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO VALIDATOR;
+step s2_begin: BEGIN;
+step s2_owner: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_handler s2_begin s2_handler s1_commit s2_commit
+step s1_begin: BEGIN;
+WARNING:  changing the foreign-data wrapper handler can change behavior of existing foreign tables
+step s1_handler: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO HANDLER;
+step s2_begin: BEGIN;
+WARNING:  changing the foreign-data wrapper handler can change behavior of existing foreign tables
+step s2_handler: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO HANDLER; <waiting ...>
+step s1_commit: COMMIT;
+step s2_handler: <... completed>
+error in steps s1_commit s2_handler: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_handler s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+WARNING:  changing the foreign-data wrapper handler can change behavior of existing foreign tables
+step s1_handler: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO HANDLER;
+step s2_begin: BEGIN;
+step s2_owner: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_owner s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_owner: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw OWNER TO CURRENT_USER;
+step s2_begin: BEGIN;
+step s2_owner: 
+	ALTER FOREIGN DATA WRAPPER regress_fdw OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
diff --git a/src/test/isolation/expected/concurrent-role.out b/src/test/isolation/expected/concurrent-role.out
new file mode 100644
index 0000000000..86bf17365d
--- /dev/null
+++ b/src/test/isolation/expected/concurrent-role.out
@@ -0,0 +1,45 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1_begin s1_alterrole_set s2_begin s2_alterrole_set s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterrole_set: 
+	ALTER ROLE regress_role_conc SET commit_delay = '10';
+step s2_begin: BEGIN;
+step s2_alterrole_set: 
+	ALTER ROLE regress_role_conc SET commit_delay = '10'; <waiting ...>
+step s1_commit: COMMIT;
+step s2_alterrole_set: <... completed>
+error in steps s1_commit s2_alterrole_set: ERROR:  duplicate key value violates unique constraint "pg_db_role_setting_databaseid_rol_index"
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterrole_set s2_begin s2_alterrole_opt s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterrole_set: 
+	ALTER ROLE regress_role_conc SET commit_delay = '10';
+step s2_begin: BEGIN;
+step s2_alterrole_opt: 
+	ALTER ROLE regress_role_conc PASSWORD 'foo';
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterrole_opt s2_begin s2_alterrole_set s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterrole_opt: 
+	ALTER ROLE regress_role_conc PASSWORD 'foo';
+step s2_begin: BEGIN;
+step s2_alterrole_set: 
+	ALTER ROLE regress_role_conc SET commit_delay = '10';
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alterrole_opt s2_begin s2_alterrole_opt s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alterrole_opt: 
+	ALTER ROLE regress_role_conc PASSWORD 'foo';
+step s2_begin: BEGIN;
+step s2_alterrole_opt: 
+	ALTER ROLE regress_role_conc PASSWORD 'foo'; <waiting ...>
+step s1_commit: COMMIT;
+step s2_alterrole_opt: <... completed>
+error in steps s1_commit s2_alterrole_opt: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
diff --git a/src/test/isolation/expected/concurrent-server.out b/src/test/isolation/expected/concurrent-server.out
new file mode 100644
index 0000000000..303569f6ce
--- /dev/null
+++ b/src/test/isolation/expected/concurrent-server.out
@@ -0,0 +1,33 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1_begin s1_options s2_begin s2_options s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_options: 
+	ALTER SERVER regress_server OPTIONS (a '1');
+step s2_begin: BEGIN;
+step s2_options: 
+	ALTER SERVER regress_server OPTIONS (a '1'); <waiting ...>
+step s1_commit: COMMIT;
+step s2_options: <... completed>
+error in steps s1_commit s2_options: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_options s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_options: 
+	ALTER SERVER regress_server OPTIONS (a '1');
+step s2_begin: BEGIN;
+step s2_owner: 
+	ALTER SERVER regress_server OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_owner s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_owner: 
+	ALTER SERVER regress_server OWNER TO CURRENT_USER;
+step s2_begin: BEGIN;
+step s2_owner: 
+	ALTER SERVER regress_server OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
diff --git a/src/test/isolation/expected/concurrent-type.out b/src/test/isolation/expected/concurrent-type.out
new file mode 100644
index 0000000000..45dbbcd130
--- /dev/null
+++ b/src/test/isolation/expected/concurrent-type.out
@@ -0,0 +1,229 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1_begin s1_add_attr s2_begin s2_add_attr s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_add_attr: 
+	ALTER TYPE regress_type ADD ATTRIBUTE b1 int;
+step s2_begin: BEGIN;
+step s2_add_attr: 
+	ALTER TYPE regress_type ADD ATTRIBUTE b2 int; <waiting ...>
+step s1_commit: COMMIT;
+step s2_add_attr: <... completed>
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_add_attr s2_begin s2_drop_attr s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_add_attr: 
+	ALTER TYPE regress_type ADD ATTRIBUTE b1 int;
+step s2_begin: BEGIN;
+step s2_drop_attr: 
+	ALTER TYPE regress_type DROP ATTRIBUTE a; <waiting ...>
+step s1_commit: COMMIT;
+step s2_drop_attr: <... completed>
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_add_attr s2_begin s2_alter_attr s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_add_attr: 
+	ALTER TYPE regress_type ADD ATTRIBUTE b1 int;
+step s2_begin: BEGIN;
+step s2_alter_attr: 
+	ALTER TYPE regress_type ALTER ATTRIBUTE a TYPE int8; <waiting ...>
+step s1_commit: COMMIT;
+step s2_alter_attr: <... completed>
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_add_attr s2_begin s2_rename_attr s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_add_attr: 
+	ALTER TYPE regress_type ADD ATTRIBUTE b1 int;
+step s2_begin: BEGIN;
+step s2_rename_attr: 
+	ALTER TYPE regress_type RENAME ATTRIBUTE a TO b; <waiting ...>
+step s1_commit: COMMIT;
+step s2_rename_attr: <... completed>
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_add_attr s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_add_attr: 
+	ALTER TYPE regress_type ADD ATTRIBUTE b1 int;
+step s2_begin: BEGIN;
+step s2_owner: 
+	ALTER TYPE regress_type OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_add_attr s2_begin s2_schema s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_add_attr: 
+	ALTER TYPE regress_type ADD ATTRIBUTE b1 int;
+step s2_begin: BEGIN;
+step s2_schema: 
+	ALTER TYPE regress_type SET SCHEMA regress_type_schema; <waiting ...>
+step s1_commit: COMMIT;
+step s2_schema: <... completed>
+error in steps s1_commit s2_schema: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_drop_attr s2_begin s2_drop_attr s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_drop_attr: 
+	ALTER TYPE regress_type DROP ATTRIBUTE a;
+step s2_begin: BEGIN;
+step s2_drop_attr: 
+	ALTER TYPE regress_type DROP ATTRIBUTE a; <waiting ...>
+step s1_commit: COMMIT;
+step s2_drop_attr: <... completed>
+error in steps s1_commit s2_drop_attr: ERROR:  column "a" of relation "regress_type" does not exist
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_drop_attr s2_begin s2_alter_attr s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_drop_attr: 
+	ALTER TYPE regress_type DROP ATTRIBUTE a;
+step s2_begin: BEGIN;
+step s2_alter_attr: 
+	ALTER TYPE regress_type ALTER ATTRIBUTE a TYPE int8; <waiting ...>
+step s1_commit: COMMIT;
+step s2_alter_attr: <... completed>
+error in steps s1_commit s2_alter_attr: ERROR:  column "a" of relation "regress_type" does not exist
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_drop_attr s2_begin s2_rename_attr s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_drop_attr: 
+	ALTER TYPE regress_type DROP ATTRIBUTE a;
+step s2_begin: BEGIN;
+step s2_rename_attr: 
+	ALTER TYPE regress_type RENAME ATTRIBUTE a TO b; <waiting ...>
+step s1_commit: COMMIT;
+step s2_rename_attr: <... completed>
+error in steps s1_commit s2_rename_attr: ERROR:  column "a" does not exist
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_drop_attr s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_drop_attr: 
+	ALTER TYPE regress_type DROP ATTRIBUTE a;
+step s2_begin: BEGIN;
+step s2_owner: 
+	ALTER TYPE regress_type OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_drop_attr s2_begin s2_schema s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_drop_attr: 
+	ALTER TYPE regress_type DROP ATTRIBUTE a;
+step s2_begin: BEGIN;
+step s2_schema: 
+	ALTER TYPE regress_type SET SCHEMA regress_type_schema;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alter_attr s2_begin s2_alter_attr s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alter_attr: 
+	ALTER TYPE regress_type ALTER ATTRIBUTE a TYPE int8;
+step s2_begin: BEGIN;
+step s2_alter_attr: 
+	ALTER TYPE regress_type ALTER ATTRIBUTE a TYPE int8; <waiting ...>
+step s1_commit: COMMIT;
+step s2_alter_attr: <... completed>
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alter_attr s2_begin s2_rename_attr s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alter_attr: 
+	ALTER TYPE regress_type ALTER ATTRIBUTE a TYPE int8;
+step s2_begin: BEGIN;
+step s2_rename_attr: 
+	ALTER TYPE regress_type RENAME ATTRIBUTE a TO b; <waiting ...>
+step s1_commit: COMMIT;
+step s2_rename_attr: <... completed>
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alter_attr s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alter_attr: 
+	ALTER TYPE regress_type ALTER ATTRIBUTE a TYPE int8;
+step s2_begin: BEGIN;
+step s2_owner: 
+	ALTER TYPE regress_type OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_alter_attr s2_begin s2_schema s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_alter_attr: 
+	ALTER TYPE regress_type ALTER ATTRIBUTE a TYPE int8;
+step s2_begin: BEGIN;
+step s2_schema: 
+	ALTER TYPE regress_type SET SCHEMA regress_type_schema;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_rename_attr s2_begin s2_rename_attr s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_rename_attr: 
+	ALTER TYPE regress_type RENAME ATTRIBUTE a TO b;
+step s2_begin: BEGIN;
+step s2_rename_attr: 
+	ALTER TYPE regress_type RENAME ATTRIBUTE a TO b; <waiting ...>
+step s1_commit: COMMIT;
+step s2_rename_attr: <... completed>
+error in steps s1_commit s2_rename_attr: ERROR:  column "a" does not exist
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_rename_attr s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_rename_attr: 
+	ALTER TYPE regress_type RENAME ATTRIBUTE a TO b;
+step s2_begin: BEGIN;
+step s2_owner: 
+	ALTER TYPE regress_type OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_rename_attr s2_begin s2_schema s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_rename_attr: 
+	ALTER TYPE regress_type RENAME ATTRIBUTE a TO b;
+step s2_begin: BEGIN;
+step s2_schema: 
+	ALTER TYPE regress_type SET SCHEMA regress_type_schema;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_owner s2_begin s2_owner s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_owner: 
+	ALTER TYPE regress_type OWNER TO CURRENT_USER;
+step s2_begin: BEGIN;
+step s2_owner: 
+	ALTER TYPE regress_type OWNER TO CURRENT_USER;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_owner s2_begin s2_schema s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_owner: 
+	ALTER TYPE regress_type OWNER TO CURRENT_USER;
+step s2_begin: BEGIN;
+step s2_schema: 
+	ALTER TYPE regress_type SET SCHEMA regress_type_schema;
+step s1_commit: COMMIT;
+step s2_commit: COMMIT;
+
+starting permutation: s1_begin s1_schema s2_begin s2_schema s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_schema: 
+	ALTER TYPE regress_type SET SCHEMA regress_type_schema;
+step s2_begin: BEGIN;
+step s2_schema: 
+	ALTER TYPE regress_type SET SCHEMA regress_type_schema; <waiting ...>
+step s1_commit: COMMIT;
+step s2_schema: <... completed>
+error in steps s1_commit s2_schema: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
diff --git a/src/test/isolation/expected/concurrent-user-mapping.out b/src/test/isolation/expected/concurrent-user-mapping.out
new file mode 100644
index 0000000000..63a89e2e88
--- /dev/null
+++ b/src/test/isolation/expected/concurrent-user-mapping.out
@@ -0,0 +1,15 @@
+Parsed test spec with 2 sessions
+
+starting permutation: s1_begin s1_options s2_begin s2_options s1_commit s2_commit
+step s1_begin: BEGIN;
+step s1_options: 
+	ALTER USER MAPPING FOR CURRENT_USER server regress_server
+	  OPTIONS (SET USER 'popo1');
+step s2_begin: BEGIN;
+step s2_options: 
+	ALTER USER MAPPING FOR CURRENT_USER server regress_server
+	  OPTIONS (SET USER 'popo1'); <waiting ...>
+step s1_commit: COMMIT;
+step s2_options: <... completed>
+error in steps s1_commit s2_options: ERROR:  tuple concurrently updated
+step s2_commit: COMMIT;
diff --git a/src/test/isolation/isolation_schedule b/src/test/isolation/isolation_schedule
index eb566ebb6c..f02a196dcc 100644
--- a/src/test/isolation/isolation_schedule
+++ b/src/test/isolation/isolation_schedule
@@ -64,3 +64,11 @@ test: async-notify
 test: vacuum-reltuples
 test: timeouts
 test: vacuum-concurrent-drop
+test: concurrent-database
+test: concurrent-role
+test: concurrent-domain
+test: concurrent-event-trigger
+test: concurrent-fdw
+test: concurrent-server
+test: concurrent-user-mapping
+test: concurrent-type
diff --git a/src/test/isolation/specs/concurrent-database.spec b/src/test/isolation/specs/concurrent-database.spec
new file mode 100644
index 0000000000..a3812abcdc
--- /dev/null
+++ b/src/test/isolation/specs/concurrent-database.spec
@@ -0,0 +1,64 @@
+# Test for interactions with DDL commands manipulating database
+# objects.
+# XXX: This cannot be included in the final patch as installcheck would
+# create a database on existing instances!
+# The following set of commands can interact in concurrency:
+# - ALTER DATABASE SET
+# - ALTER DATABASE OWNER TO
+# - ALTER DATABASE SET TABLESPACE
+# - ALTER DATABASE WITH
+
+setup
+{
+  CREATE DATABASE regress_database TEMPLATE template0;
+}
+
+teardown
+{
+  DROP DATABASE regress_database;
+}
+
+session "s1"
+step "s1_begin"			{ BEGIN; }
+step "s1_alterdb_with"	{
+	ALTER DATABASE regress_database WITH ALLOW_CONNECTIONS true; }
+step "s1_alterdb_set"	{
+	ALTER DATABASE regress_database SET commit_delay = '10'; }
+step "s1_alterdb_owner"	{
+	ALTER DATABASE regress_database OWNER TO CURRENT_USER; }
+step "s1_alterdb_tbc"	{
+	ALTER DATABASE regress_database SET TABLESPACE TO DEFAULT; }
+step "s1_commit"	{ COMMIT; }
+
+session "s2"
+step "s2_begin"			{ BEGIN; }
+step "s2_alterdb_with"	{
+	ALTER DATABASE regress_database WITH ALLOW_CONNECTIONS true; }
+step "s2_alterdb_set"	{
+	ALTER DATABASE regress_database SET commit_delay = '10'; }
+step "s2_alterdb_owner"	{
+	ALTER DATABASE regress_database OWNER TO CURRENT_USER; }
+step "s2_alterdb_tbc"	{
+	ALTER DATABASE regress_database SET TABLESPACE TO DEFAULT; }
+step "s2_commit"	{ COMMIT; }
+
+permutation "s1_begin" "s1_alterdb_with" "s2_begin" "s2_alterdb_with"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterdb_with" "s2_begin" "s2_alterdb_set"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterdb_with" "s2_begin" "s2_alterdb_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterdb_with" "s2_begin" "s2_alterdb_tbc"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterdb_set" "s2_begin" "s2_alterdb_set"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterdb_set" "s2_begin" "s2_alterdb_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterdb_set" "s2_begin" "s2_alterdb_tbc"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterdb_owner" "s2_begin" "s2_alterdb_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterdb_owner" "s2_begin" "s2_alterdb_tbc"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterdb_tbc" "s2_begin" "s2_alterdb_tbc"
+	"s1_commit" "s2_commit"
diff --git a/src/test/isolation/specs/concurrent-domain.spec b/src/test/isolation/specs/concurrent-domain.spec
new file mode 100644
index 0000000000..1525a53c42
--- /dev/null
+++ b/src/test/isolation/specs/concurrent-domain.spec
@@ -0,0 +1,191 @@
+# Test for interactions with DDL commands manipulating domain
+# objects.
+# The following set of commands can interact in concurrency:
+# - ALTER DOMAIN SET NOT NULL
+# - ALTER DOMAIN DROP NOT NULL
+# - ALTER DOMAIN SET DEFAULT
+# - ALTER DOMAIN DROP DEFAULT
+# - ALTER DOMAIN ADD CONSTRAINT
+# - ALTER DOMAIN DROP CONSTRAINT
+# - ALTER DOMAIN VALIDATE CONSTRAINT
+# - ALTER DOMAIN OWNER TO
+# - ALTER DOMAIN SET SCHEMA
+
+setup
+{
+  CREATE SCHEMA regress_domain_schema;
+  CREATE DOMAIN regress_domain_conc AS int;
+}
+
+teardown
+{
+  DROP DOMAIN IF EXISTS regress_domain_conc;
+  DROP SCHEMA regress_domain_schema CASCADE;
+
+}
+
+session "s1"
+step "s1_begin"				{ BEGIN; }
+step "s1_dom_set_notnull"	{
+	ALTER DOMAIN regress_domain_conc SET NOT NULL; }
+step "s1_dom_drop_notnull"	{
+	ALTER DOMAIN regress_domain_conc DROP NOT NULL; }
+step "s1_dom_set_default"	{
+	ALTER DOMAIN regress_domain_conc SET DEFAULT 1; }
+step "s1_dom_drop_default"	{
+	ALTER DOMAIN regress_domain_conc DROP DEFAULT; }
+step "s1_dom_add_con"		{
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0); }
+step "s1_dom_drop_con"		{
+	ALTER DOMAIN regress_domain_conc DROP CONSTRAINT dom_con; }
+step "s1_dom_validate_con"	{
+	ALTER DOMAIN regress_domain_conc VALIDATE CONSTRAINT dom_con; }
+step "s1_dom_owner"			{
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER; }
+step "s1_dom_schema_priv"	{
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema; }
+step "s1_dom_schema_publ"	{
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public; }
+step "s1_commit"			{ COMMIT; }
+
+session "s2"
+step "s2_begin"			{ BEGIN; }
+step "s2_dom_set_notnull"	{
+	ALTER DOMAIN regress_domain_conc SET NOT NULL; }
+step "s2_dom_drop_notnull"	{
+	ALTER DOMAIN regress_domain_conc DROP NOT NULL; }
+step "s2_dom_set_default"	{
+	ALTER DOMAIN regress_domain_conc SET DEFAULT 1; }
+step "s2_dom_drop_default"	{
+	ALTER DOMAIN regress_domain_conc DROP DEFAULT; }
+step "s2_dom_add_con"		{
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con CHECK (VALUE > 0); }
+step "s2_dom_add_con2"		{
+	ALTER DOMAIN regress_domain_conc ADD CONSTRAINT dom_con2 CHECK (VALUE > 0); }
+step "s2_dom_drop_con"		{
+	ALTER DOMAIN regress_domain_conc DROP CONSTRAINT dom_con; }
+step "s2_dom_validate_con"	{
+	ALTER DOMAIN regress_domain_conc VALIDATE CONSTRAINT dom_con; }
+step "s2_dom_owner"			{
+	ALTER DOMAIN regress_domain_conc OWNER TO CURRENT_USER; }
+step "s2_dom_schema_priv"	{
+	ALTER DOMAIN regress_domain_conc SET SCHEMA regress_domain_schema; }
+step "s2_dom_schema_publ"	{
+	ALTER DOMAIN regress_domain_conc SET SCHEMA public; }
+step "s2_commit"	{ COMMIT; }
+
+# Round 1 of all permutations using SET NOT NULL as base
+permutation "s1_begin" "s1_dom_set_notnull" "s2_begin" "s2_dom_set_notnull"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_set_notnull" "s2_begin" "s2_dom_drop_notnull"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_set_notnull" "s2_begin" "s2_dom_set_default"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_set_notnull" "s2_begin" "s2_dom_drop_default"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_set_notnull" "s2_begin" "s2_dom_add_con"
+	"s1_commit" "s2_commit"
+# No DROP/VALIDATE CONSTRAINT needed as nothing is defined.
+permutation "s1_begin" "s1_dom_set_notnull" "s2_begin" "s2_dom_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_set_notnull" "s2_begin" "s2_dom_schema_priv"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_set_notnull" "s2_begin" "s2_dom_schema_publ"
+	"s1_commit" "s2_commit"
+
+# Round 2 of all permutations using DROP NOT NULL as base
+permutation "s1_begin" "s1_dom_drop_notnull" "s2_begin" "s2_dom_drop_notnull"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_drop_notnull" "s2_begin" "s2_dom_set_default"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_drop_notnull" "s2_begin" "s2_dom_drop_default"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_drop_notnull" "s2_begin" "s2_dom_add_con"
+	"s1_commit" "s2_commit"
+# No DROP/VALIDATE CONSTRAINT needed as nothing is defined.
+permutation "s1_begin" "s1_dom_drop_notnull" "s2_begin" "s2_dom_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_drop_notnull" "s2_begin" "s2_dom_schema_priv"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_drop_notnull" "s2_begin" "s2_dom_schema_publ"
+	"s1_commit" "s2_commit"
+
+# Round 3 of all permutations using SET DEFAULT as base
+permutation "s1_begin" "s1_dom_set_default" "s2_begin" "s2_dom_set_default"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_set_default" "s2_begin" "s2_dom_drop_default"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_set_default" "s2_begin" "s2_dom_add_con"
+	"s1_commit" "s2_commit"
+# No DROP/VALIDATE CONSTRAINT needed as nothing is defined.
+permutation "s1_begin" "s1_dom_set_default" "s2_begin" "s2_dom_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_set_default" "s2_begin" "s2_dom_schema_priv"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_set_default" "s2_begin" "s2_dom_schema_publ"
+	"s1_commit" "s2_commit"
+
+# Round 4 of all permutations using DROP DEFAULT as base
+permutation "s1_begin" "s1_dom_drop_default" "s2_begin" "s2_dom_drop_default"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_drop_default" "s2_begin" "s2_dom_add_con"
+	"s1_commit" "s2_commit"
+# No DROP/VALIDATE CONSTRAINT needed as nothing is defined.
+permutation "s1_begin" "s1_dom_drop_default" "s2_begin" "s2_dom_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_drop_default" "s2_begin" "s2_dom_schema_priv"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_drop_default" "s2_begin" "s2_dom_schema_publ"
+	"s1_commit" "s2_commit"
+
+# Round 5 of all permutations using ADD CONSTRAINT as a base
+permutation "s1_begin" "s1_dom_add_con" "s2_begin" "s2_dom_add_con2"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_add_con" "s2_begin" "s2_dom_drop_con"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_add_con" "s2_begin" "s2_dom_validate_con"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_add_con" "s2_begin" "s2_dom_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_add_con" "s2_begin" "s2_dom_schema_priv"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_add_con" "s2_begin" "s2_dom_schema_publ"
+	"s1_commit" "s2_commit"
+
+# Round 6 with DROP CONSTRAINT
+permutation "s1_dom_add_con" "s1_begin" "s1_dom_drop_con" "s2_begin"
+	"s2_dom_drop_con" "s1_commit" "s2_commit"
+permutation "s1_dom_add_con" "s1_begin" "s1_dom_drop_con" "s2_begin"
+	"s2_dom_validate_con" "s1_commit" "s2_commit"
+permutation "s1_dom_add_con" "s1_begin" "s1_dom_drop_con" "s2_begin"
+	"s2_dom_owner" "s1_commit" "s2_commit"
+permutation "s1_dom_add_con" "s1_begin" "s1_dom_drop_con" "s2_begin"
+	"s2_dom_schema_publ" "s1_commit" "s2_commit"
+permutation "s1_dom_add_con" "s1_begin" "s1_dom_drop_con" "s2_begin"
+	"s2_dom_schema_priv" "s1_commit" "s2_commit"
+
+# Round 7 of all permutations using VALIDATE CONSTRAINT
+permutation "s1_dom_add_con" "s1_begin" "s1_dom_validate_con" "s2_begin"
+	"s2_dom_validate_con" "s1_commit" "s2_commit"
+permutation "s1_dom_add_con" "s1_begin" "s1_dom_validate_con" "s2_begin"
+	"s2_dom_owner" "s1_commit" "s2_commit"
+permutation "s1_dom_add_con" "s1_begin" "s1_dom_validate_con" "s2_begin"
+	"s2_dom_schema_priv" "s1_commit" "s2_commit"
+permutation "s1_dom_add_con" "s1_begin" "s1_dom_validate_con" "s2_begin"
+	"s2_dom_schema_publ" "s1_commit" "s2_commit"
+
+# Round 8 of all permutations using OWNER TO as base
+permutation "s1_begin" "s1_dom_owner" "s2_begin" "s2_dom_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_owner" "s2_begin" "s2_dom_schema_priv"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_owner" "s2_begin" "s2_dom_schema_publ"
+	"s1_commit" "s2_commit"
+
+# Round 9 with schemas
+permutation "s1_begin" "s1_dom_schema_priv" "s2_begin" "s2_dom_schema_publ"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_schema_publ" "s2_begin" "s2_dom_schema_priv"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_dom_schema_publ" "s2_begin" "s2_dom_schema_publ"
+	"s1_commit" "s2_commit"
diff --git a/src/test/isolation/specs/concurrent-event-trigger.spec b/src/test/isolation/specs/concurrent-event-trigger.spec
new file mode 100644
index 0000000000..f896f0754c
--- /dev/null
+++ b/src/test/isolation/specs/concurrent-event-trigger.spec
@@ -0,0 +1,53 @@
+# Test for interactions with DDL commands manipulating event trigger
+# objects.
+# The following set of commands can interact in concurrency:
+# - ALTER EVENT TRIGGER ENABLE
+# - ALTER EVENT TRIGGER DISABLE
+# - ALTER EVENT TRIGGER OWNER TO
+
+setup
+{
+  CREATE OR REPLACE FUNCTION notice_any_command()
+    RETURNS event_trigger
+    LANGUAGE plpgsql
+    AS $$
+      BEGIN
+      RAISE NOTICE 'command % is run', tg_tag;
+      END;
+    $$;
+  CREATE EVENT TRIGGER notice_ddl ON ddl_command_start
+     EXECUTE PROCEDURE notice_any_command();
+}
+
+teardown
+{
+  DROP EVENT TRIGGER notice_ddl;
+  DROP FUNCTION notice_any_command();
+}
+
+session "s1"
+step "s1_begin"		{ BEGIN; }
+step "s1_disable"	{ ALTER EVENT TRIGGER notice_ddl DISABLE; }
+step "s1_enable"	{ ALTER EVENT TRIGGER notice_ddl ENABLE REPLICA; }
+step "s1_owner"		{ ALTER EVENT TRIGGER notice_ddl OWNER TO CURRENT_USER; }
+step "s1_commit"	{ COMMIT; }
+
+session "s2"
+step "s2_begin"		{ BEGIN; }
+step "s2_disable"	{ ALTER EVENT TRIGGER notice_ddl DISABLE; }
+step "s2_enable"	{ ALTER EVENT TRIGGER notice_ddl ENABLE REPLICA; }
+step "s2_owner"		{ ALTER EVENT TRIGGER notice_ddl OWNER TO CURRENT_USER; }
+step "s2_commit"	{ COMMIT; }
+
+permutation "s1_begin" "s1_disable" "s2_begin" "s2_disable"
+  "s1_commit" "s2_commit"
+permutation "s1_begin" "s1_disable" "s2_begin" "s2_enable"
+  "s1_commit" "s2_commit"
+permutation "s1_begin" "s1_disable" "s2_begin" "s2_owner"
+  "s1_commit" "s2_commit"
+permutation "s1_begin" "s1_enable" "s2_begin" "s2_enable"
+  "s1_commit" "s2_commit"
+permutation "s1_begin" "s1_enable" "s2_begin" "s2_owner"
+  "s1_commit" "s2_commit"
+permutation "s1_begin" "s1_owner" "s2_begin" "s2_owner"
+  "s1_commit" "s2_commit"
diff --git a/src/test/isolation/specs/concurrent-fdw.spec b/src/test/isolation/specs/concurrent-fdw.spec
new file mode 100644
index 0000000000..1e8ce38dad
--- /dev/null
+++ b/src/test/isolation/specs/concurrent-fdw.spec
@@ -0,0 +1,62 @@
+# Test for interactions with DDL commands manipulating fdw
+# objects.
+# The following set of commands can interact in concurrency:
+# - ALTER FDW OPTIONS
+# - ALTER FDW VALIDATOR
+# - ALTER FDW HANDLER
+# - ALTER FDW OWNER TO
+
+setup
+{
+  CREATE FOREIGN DATA WRAPPER regress_fdw;
+}
+
+teardown
+{
+  DROP FOREIGN DATA WRAPPER regress_fdw;
+}
+
+session "s1"
+step "s1_begin"			{ BEGIN; }
+step "s1_options"	{
+	ALTER FOREIGN DATA WRAPPER regress_fdw OPTIONS (a '1'); }
+step "s1_validator"	{
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO VALIDATOR; }
+step "s1_handler"	{
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO HANDLER; }
+step "s1_owner"	{
+	ALTER FOREIGN DATA WRAPPER regress_fdw OWNER TO CURRENT_USER; }
+step "s1_commit"	{ COMMIT; }
+
+session "s2"
+step "s2_begin"			{ BEGIN; }
+step "s2_options"	{
+	ALTER FOREIGN DATA WRAPPER regress_fdw OPTIONS (a '1'); }
+step "s2_validator"	{
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO VALIDATOR; }
+step "s2_handler"	{
+	ALTER FOREIGN DATA WRAPPER regress_fdw NO HANDLER; }
+step "s2_owner"	{
+	ALTER FOREIGN DATA WRAPPER regress_fdw OWNER TO CURRENT_USER; }
+step "s2_commit"	{ COMMIT; }
+
+permutation "s1_begin" "s1_options" "s2_begin" "s2_options"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_options" "s2_begin" "s2_validator"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_options" "s2_begin" "s2_handler"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_options" "s2_begin" "s2_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_validator" "s2_begin" "s2_validator"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_validator" "s2_begin" "s2_handler"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_validator" "s2_begin" "s2_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_handler" "s2_begin" "s2_handler"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_handler" "s2_begin" "s2_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_owner" "s2_begin" "s2_owner"
+	"s1_commit" "s2_commit"
diff --git a/src/test/isolation/specs/concurrent-role.spec b/src/test/isolation/specs/concurrent-role.spec
new file mode 100644
index 0000000000..24b96da41a
--- /dev/null
+++ b/src/test/isolation/specs/concurrent-role.spec
@@ -0,0 +1,40 @@
+# Test for interactions with DDL commands manipulating role
+# objects.
+# The following set of commands can interact in concurrency:
+# - ALTER ROLE SET
+# - ALTER ROLE option
+
+setup
+{
+  CREATE ROLE regress_role_conc;
+}
+
+teardown
+{
+  DROP ROLE regress_role_conc;
+}
+
+session "s1"
+step "s1_begin"			{ BEGIN; }
+step "s1_alterrole_set"	{
+	ALTER ROLE regress_role_conc SET commit_delay = '10'; }
+step "s1_alterrole_opt"	{
+	ALTER ROLE regress_role_conc PASSWORD 'foo'; }
+step "s1_commit"	{ COMMIT; }
+
+session "s2"
+step "s2_begin"			{ BEGIN; }
+step "s2_alterrole_set"	{
+	ALTER ROLE regress_role_conc SET commit_delay = '10'; }
+step "s2_alterrole_opt"	{
+	ALTER ROLE regress_role_conc PASSWORD 'foo'; }
+step "s2_commit"	{ COMMIT; }
+
+permutation "s1_begin" "s1_alterrole_set" "s2_begin" "s2_alterrole_set"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterrole_set" "s2_begin" "s2_alterrole_opt"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterrole_opt" "s2_begin" "s2_alterrole_set"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alterrole_opt" "s2_begin" "s2_alterrole_opt"
+	"s1_commit" "s2_commit"
diff --git a/src/test/isolation/specs/concurrent-server.spec b/src/test/isolation/specs/concurrent-server.spec
new file mode 100644
index 0000000000..2a41d09397
--- /dev/null
+++ b/src/test/isolation/specs/concurrent-server.spec
@@ -0,0 +1,39 @@
+# Test for interactions with DDL commands manipulating server
+# objects.
+# The following set of commands can interact in concurrency:
+# - ALTER SERVER OPTIONS
+# - ALTER SERVER OWNER TO
+
+setup
+{
+  CREATE FOREIGN DATA WRAPPER regress_fdw;
+  CREATE SERVER regress_server FOREIGN DATA WRAPPER regress_fdw;
+}
+
+teardown
+{
+  DROP FOREIGN DATA WRAPPER regress_fdw CASCADE;
+}
+
+session "s1"
+step "s1_begin"		{ BEGIN; }
+step "s1_options"	{
+	ALTER SERVER regress_server OPTIONS (a '1'); }
+step "s1_owner"		{
+	ALTER SERVER regress_server OWNER TO CURRENT_USER; }
+step "s1_commit"	{ COMMIT; }
+
+session "s2"
+step "s2_begin"			{ BEGIN; }
+step "s2_options"	{
+	ALTER SERVER regress_server OPTIONS (a '1'); }
+step "s2_owner"		{
+	ALTER SERVER regress_server OWNER TO CURRENT_USER; }
+step "s2_commit"	{ COMMIT; }
+
+permutation "s1_begin" "s1_options" "s2_begin" "s2_options"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_options" "s2_begin" "s2_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_owner" "s2_begin" "s2_owner"
+	"s1_commit" "s2_commit"
diff --git a/src/test/isolation/specs/concurrent-type.spec b/src/test/isolation/specs/concurrent-type.spec
new file mode 100644
index 0000000000..3fe8f2338b
--- /dev/null
+++ b/src/test/isolation/specs/concurrent-type.spec
@@ -0,0 +1,107 @@
+# Test for interactions with DDL commands manipulating type
+# objects.
+# The following set of commands can interact in concurrency:
+# - ALTER TYPE ADD ATTRIBUTE
+# - ALTER TYPE DROP ATTRIBUTE
+# - ALTER TYPE ALTER ATTRIBUTE
+# - ALTER TYPE RENAME ATTRIBUTE
+# - ALTER TYPE OWNER TO
+# - ALTER TYPE SET SCHEMA
+
+setup
+{
+  CREATE SCHEMA regress_type_schema;
+  CREATE TYPE regress_type AS (a int);
+}
+
+teardown
+{
+  DROP TYPE IF EXISTS regress_type;
+  DROP SCHEMA regress_type_schema CASCADE;
+}
+
+session "s1"
+step "s1_begin"			{ BEGIN; }
+step "s1_add_attr"		{
+	ALTER TYPE regress_type ADD ATTRIBUTE b1 int; }
+step "s1_drop_attr"		{
+	ALTER TYPE regress_type DROP ATTRIBUTE a; }
+step "s1_alter_attr"	{
+	ALTER TYPE regress_type ALTER ATTRIBUTE a TYPE int8; }
+step "s1_rename_attr"	{
+	ALTER TYPE regress_type RENAME ATTRIBUTE a TO b; }
+step "s1_owner"			{
+	ALTER TYPE regress_type OWNER TO CURRENT_USER; }
+step "s1_schema"		{
+	ALTER TYPE regress_type SET SCHEMA regress_type_schema; }
+step "s1_commit"	{ COMMIT; }
+
+session "s2"
+step "s2_begin"		{ BEGIN; }
+step "s2_add_attr"		{
+	ALTER TYPE regress_type ADD ATTRIBUTE b2 int; }
+step "s2_drop_attr"		{
+	ALTER TYPE regress_type DROP ATTRIBUTE a; }
+step "s2_alter_attr"	{
+	ALTER TYPE regress_type ALTER ATTRIBUTE a TYPE int8; }
+step "s2_rename_attr"	{
+	ALTER TYPE regress_type RENAME ATTRIBUTE a TO b; }
+step "s2_owner"			{
+	ALTER TYPE regress_type OWNER TO CURRENT_USER; }
+step "s2_schema"		{
+	ALTER TYPE regress_type SET SCHEMA regress_type_schema; }
+step "s2_commit"	{ COMMIT; }
+
+# Round 1 of permutations based on ADD ATTRIBUTE
+permutation "s1_begin" "s1_add_attr" "s2_begin" "s2_add_attr"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_add_attr" "s2_begin" "s2_drop_attr"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_add_attr" "s2_begin" "s2_alter_attr"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_add_attr" "s2_begin" "s2_rename_attr"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_add_attr" "s2_begin" "s2_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_add_attr" "s2_begin" "s2_schema"
+	"s1_commit" "s2_commit"
+
+# Round 2 of permutations based on DROP ATTRIBUTE
+permutation "s1_begin" "s1_drop_attr" "s2_begin" "s2_drop_attr"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_drop_attr" "s2_begin" "s2_alter_attr"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_drop_attr" "s2_begin" "s2_rename_attr"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_drop_attr" "s2_begin" "s2_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_drop_attr" "s2_begin" "s2_schema"
+	"s1_commit" "s2_commit"
+
+# Round 3 of permutations based on ALTER ATTRIBUTE
+permutation "s1_begin" "s1_alter_attr" "s2_begin" "s2_alter_attr"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alter_attr" "s2_begin" "s2_rename_attr"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alter_attr" "s2_begin" "s2_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_alter_attr" "s2_begin" "s2_schema"
+	"s1_commit" "s2_commit"
+
+# Round 4 of permutations based on RENAME ATTRIBUTE
+permutation "s1_begin" "s1_rename_attr" "s2_begin" "s2_rename_attr"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_rename_attr" "s2_begin" "s2_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_rename_attr" "s2_begin" "s2_schema"
+	"s1_commit" "s2_commit"
+
+# Round 5 of permutations based on OWNER TO
+permutation "s1_begin" "s1_owner" "s2_begin" "s2_owner"
+	"s1_commit" "s2_commit"
+permutation "s1_begin" "s1_owner" "s2_begin" "s2_schema"
+	"s1_commit" "s2_commit"
+
+# Round 6 of permutations based on SET SCHEMA
+permutation "s1_begin" "s1_schema" "s2_begin" "s2_schema"
+	"s1_commit" "s2_commit"
diff --git a/src/test/isolation/specs/concurrent-user-mapping.spec b/src/test/isolation/specs/concurrent-user-mapping.spec
new file mode 100644
index 0000000000..d8a8669c4f
--- /dev/null
+++ b/src/test/isolation/specs/concurrent-user-mapping.spec
@@ -0,0 +1,34 @@
+# Test for interactions with DDL commands manipulating user
+# mappings
+# The following set of commands can interact in concurrency:
+# - ALTER USER MAPPING OPTIONS
+
+setup
+{
+  CREATE FOREIGN DATA WRAPPER regress_fdw;
+  CREATE SERVER regress_server FOREIGN DATA WRAPPER regress_fdw;
+  CREATE USER MAPPING FOR CURRENT_USER SERVER regress_server
+    OPTIONS (user 'CURRENT_USER');
+}
+
+teardown
+{
+  DROP FOREIGN DATA WRAPPER regress_fdw CASCADE;
+}
+
+session "s1"
+step "s1_begin"		{ BEGIN; }
+step "s1_options"	{
+	ALTER USER MAPPING FOR CURRENT_USER server regress_server
+	  OPTIONS (SET USER 'popo1'); }
+step "s1_commit"	{ COMMIT; }
+
+session "s2"
+step "s2_begin"		{ BEGIN; }
+step "s2_options"	{
+	ALTER USER MAPPING FOR CURRENT_USER server regress_server
+	  OPTIONS (SET USER 'popo1'); }
+step "s2_commit"	{ COMMIT; }
+
+permutation "s1_begin" "s1_options" "s2_begin" "s2_options"
+	"s1_commit" "s2_commit"