3 files changed, 87 insertions, 1 deletions
diff --git a/contrib/test_decoding/Makefile b/contrib/test_decoding/Makefile
index d7f32c3ec58..2e5a01bd730 100644
--- a/contrib/test_decoding/Makefile
+++ b/contrib/test_decoding/Makefile
@@ -53,7 +53,7 @@ regresscheck-install-force: | submake-regress submake-test_decoding
 	    --extra-install=contrib/test_decoding \
 	    $(REGRESSCHECKS)
 
-ISOLATIONCHECKS=mxact delayed_startup concurrent_ddl_dml
+ISOLATIONCHECKS=mxact delayed_startup ondisk_startup concurrent_ddl_dml
 
 isolationcheck: all | submake-isolation submake-test_decoding
 	$(MKDIR_P) isolation_output
diff --git a/contrib/test_decoding/expected/ondisk_startup.out b/contrib/test_decoding/expected/ondisk_startup.out
new file mode 100644
index 00000000000..65115c830a4
--- /dev/null
+++ b/contrib/test_decoding/expected/ondisk_startup.out
@@ -0,0 +1,43 @@
+Parsed test spec with 3 sessions
+
+starting permutation: s2txid s1init s3txid s2alter s2c s1insert s1checkpoint s1start s1insert s1alter s1insert s1start
+step s2txid: BEGIN ISOLATION LEVEL REPEATABLE READ; SELECT txid_current() IS NULL;
+?column?       
+
+f              
+step s1init: SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding'); <waiting ...>
+step s3txid: BEGIN ISOLATION LEVEL REPEATABLE READ; SELECT txid_current() IS NULL;
+?column?       
+
+f              
+step s2alter: ALTER TABLE do_write ADD COLUMN addedbys2 int;
+step s2c: COMMIT;
+step s1init: <... completed>
+?column?       
+
+init           
+step s1insert: INSERT INTO do_write DEFAULT VALUES;
+step s1checkpoint: CHECKPOINT;
+step s1start: SELECT data FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false');
+data           
+
+BEGIN          
+table public.do_write: INSERT: id[integer]:1 addedbys2[integer]:null
+COMMIT         
+step s1insert: INSERT INTO do_write DEFAULT VALUES;
+step s1alter: ALTER TABLE do_write ADD COLUMN addedbys1 int;
+step s1insert: INSERT INTO do_write DEFAULT VALUES;
+step s1start: SELECT data FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false');
+data           
+
+BEGIN          
+table public.do_write: INSERT: id[integer]:2 addedbys2[integer]:null
+COMMIT         
+BEGIN          
+COMMIT         
+BEGIN          
+table public.do_write: INSERT: id[integer]:3 addedbys2[integer]:null addedbys1[integer]:null
+COMMIT         
+?column?       
+
+stop           
diff --git a/contrib/test_decoding/specs/ondisk_startup.spec b/contrib/test_decoding/specs/ondisk_startup.spec
new file mode 100644
index 00000000000..39c4a223aee
--- /dev/null
+++ b/contrib/test_decoding/specs/ondisk_startup.spec
@@ -0,0 +1,43 @@
+# Force usage of ondisk decoding snapshots to test that code path.
+setup
+{
+    DROP TABLE IF EXISTS do_write;
+    CREATE TABLE do_write(id serial primary key);
+}
+
+teardown
+{
+    DROP TABLE do_write;
+    SELECT 'stop' FROM pg_drop_replication_slot('isolation_slot');
+}
+
+
+session "s1"
+setup { SET synchronous_commit=on; }
+
+step "s1init" {SELECT 'init' FROM pg_create_logical_replication_slot('isolation_slot', 'test_decoding');}
+step "s1start" {SELECT data FROM pg_logical_slot_get_changes('isolation_slot', NULL, NULL, 'include-xids', 'false');}
+step "s1insert" { INSERT INTO do_write DEFAULT VALUES; }
+step "s1checkpoint" { CHECKPOINT; }
+step "s1alter" { ALTER TABLE do_write ADD COLUMN addedbys1 int; }
+
+session "s2"
+setup { SET synchronous_commit=on; }
+
+step "s2txid" { BEGIN ISOLATION LEVEL REPEATABLE READ; SELECT txid_current() IS NULL; }
+step "s2alter" { ALTER TABLE do_write ADD COLUMN addedbys2 int; }
+step "s2c" { COMMIT; }
+
+
+session "s3"
+setup { SET synchronous_commit=on; }
+
+step "s3txid" { BEGIN ISOLATION LEVEL REPEATABLE READ; SELECT txid_current() IS NULL; }
+step "s3c" { COMMIT; }
+
+# Force usage of ondisk snapshot by starting and not finishing a
+# transaction with a assigned xid after consistency has been
+# reached. In combination with a checkpoint forcing a snapshot to be
+# written and a new restart point computed that'll lead to the usage
+# of the snapshot.
+permutation "s2txid" "s1init" "s3txid" "s2alter" "s2c" "s1insert" "s1checkpoint" "s1start" "s1insert" "s1alter" "s1insert" "s1start"