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From: [email protected] <[email protected]>
To: Amit Kapila <[email protected]>
To: [email protected] <[email protected]>
Cc: Peter Smith <[email protected]>
Cc: Dilip Kumar <[email protected]>
Cc: Masahiko Sawada <[email protected]>
Cc: [email protected] <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: RE: Perform streaming logical transactions by background workers and parallel apply
Date: Thu, 15 Sep 2022 05:15:24 +0000
Message-ID: <OS3PR01MB6275F145878B4A44586C46CE9E499@OS3PR01MB6275.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <CAA4eK1Lu-6oXMk7ZaGYLwm3CRLBuzueGbasyHnNpJxu6Mq3mmg@mail.gmail.com>
References: <OS0PR01MB5716730C06159452335D870D947F9@OS0PR01MB5716.jpnprd01.prod.outlook.com>
	<CAA4eK1Lu-6oXMk7ZaGYLwm3CRLBuzueGbasyHnNpJxu6Mq3mmg@mail.gmail.com>

On Thur, Sep 8, 2022 at 14:52 PM Amit Kapila <[email protected]> wrote:
> On Mon, Sep 5, 2022 at 6:34 PM [email protected]
> <[email protected]> wrote:
> >
> > Attach the correct patch set this time.
> >
> 
> Few comments on v28-0001*:

Thanks for your comments.

> 1.
> + /* Whether the worker is processing a transaction. */
> + bool in_use;
> 
> I think this same comment applies to in_parallel_apply_xact flag as
> well. How about: "Indicates whether the worker is available to be used
> for parallel apply transaction?"?
> 
> 2.
> + /*
> + * Set this flag in the leader instead of the parallel apply worker to
> + * avoid the race condition where the leader has already started waiting
> + * for the parallel apply worker to finish processing the transaction(set
> + * the in_parallel_apply_xact to false) while the child process has not yet
> + * processed the first STREAM_START and has not set the
> + * in_parallel_apply_xact to true.
> 
> I think part of this comment "(set the in_parallel_apply_xact to
> false)" is not necessary. It will be clear without that.
> 
> 3.
> + /* Create entry for requested transaction. */
> + entry = hash_search(ParallelApplyWorkersHash, &xid, HASH_ENTER, &found);
> + if (found)
> + elog(ERROR, "hash table corrupted");
> ...
> ...
> + hash_search(ParallelApplyWorkersHash, &xid, HASH_REMOVE, NULL);
> 
> It is better to have a similar elog for HASH_REMOVE case as well. We
> normally seem to have such elog for HASH_REMOVE.
> 
> 4.
> * Parallel apply is not supported when subscribing to a publisher which
> +     * cannot provide the abort_time, abort_lsn and the column information
> used
> +     * to verify the parallel apply safety.
> 
> 
> In this comment, which column information are you referring to?
> 
> 5.
> + /*
> + * Set in_parallel_apply_xact to true again as we only aborted the
> + * subtransaction and the top transaction is still in progress. No
> + * need to lock here because currently only the apply leader are
> + * accessing this flag.
> + */
> + winfo->shared->in_parallel_apply_xact = true;
> 
> This theory sounds good to me but I think it is better to update/read
> this flag under spinlock as the patch is doing at a few other places.
> I think that will make the code easier to follow without worrying too
> much about such special cases. There are a few asserts as well which
> read this without lock, it would be better to change those as well.
> 
> 6.
> + * LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM is the minimum
> protocol version
> + * with support for streaming large transactions using parallel apply
> + * workers. Introduced in PG16.
> 
> How about changing it to something like:
> "LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM is the minimum
> protocol
> version where we support applying large streaming transactions in
> parallel. Introduced in PG16."
> 
> 7.
> + PGOutputData *data = (PGOutputData *) ctx->output_plugin_private;
> + bool write_abort_lsn = (data->protocol_version >=
> + LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM);
> 
>   /*
>   * The abort should happen outside streaming block, even for streamed
> @@ -1856,7 +1859,8 @@ pgoutput_stream_abort(struct
> LogicalDecodingContext *ctx,
>   Assert(rbtxn_is_streamed(toptxn));
> 
>   OutputPluginPrepareWrite(ctx, true);
> - logicalrep_write_stream_abort(ctx->out, toptxn->xid, txn->xid);
> + logicalrep_write_stream_abort(ctx->out, toptxn->xid, txn, abort_lsn,
> +   write_abort_lsn);
> 
> I think we need to send additional information if the client has used
> the parallel streaming option. Also, let's keep sending subxid as we
> were doing previously and add additional parameters required. It may
> be better to name write_abort_lsn as abort_info.
> 
> 8.
> + /*
> + * Check whether the publisher sends abort_lsn and abort_time.
> + *
> + * Note that the paralle apply worker is only started when the publisher
> + * sends abort_lsn and abort_time.
> + */
> + if (am_parallel_apply_worker() ||
> + walrcv_server_version(LogRepWorkerWalRcvConn) >= 160000)
> + read_abort_lsn = true;
> +
> + logicalrep_read_stream_abort(s, &abort_data, read_abort_lsn);
> 
> This check should match with the check for the write operation where
> we are checking the protocol version as well. There is a typo as well
> in the comments (/paralle/parallel).

Improved as suggested.

Attach the new patch set.

Regards,
Wang wei


Attachments:

  [application/octet-stream] v29-0001-Perform-streaming-logical-transactions-by-parall.patch (137.0K, ../OS3PR01MB6275F145878B4A44586C46CE9E499@OS3PR01MB6275.jpnprd01.prod.outlook.com/2-v29-0001-Perform-streaming-logical-transactions-by-parall.patch)
  download | inline diff:
From 967c5912b0a277413ae85bd06951136dc6f35ae4 Mon Sep 17 00:00:00 2001
From: "houzj.fnst" <[email protected]>
Date: Wed, 20 Apr 2022 16:45:07 +0800
Subject: [PATCH v29 1/5] Perform streaming logical transactions by parallel
 workers

Currently, for large transactions, the publisher sends the data in multiple
streams (changes divided into chunks depending upon logical_decoding_work_mem),
and then on the subscriber-side, the apply worker writes the changes into
temporary files and once it receives the commit, it reads from the file and
applies the entire transaction. To improve the performance of such
transactions, we can instead allow them to be applied via parallel workers.

In this approach, we assign a new parallel apply worker (if available) as
soon as the xact's first stream is received and the leader apply worker will
send changes to this new worker via shared memory. The parallel apply worker
will directly apply the change instead of writing it to temporary files. We
keep this worker assigned till the transaction commit is received and also wait
for the worker to finish at commit. This preserves commit ordering and avoids
writing to and reading from file in most cases. We still need to spill if there
is no worker available.

This patch also extends the SUBSCRIPTION 'streaming' parameter so that the user
can control whether to apply the streaming transaction in a parallel apply
worker or spill the change to disk. The user can set the streaming parameter to
'on/off', 'parallel'. The parameter value 'parallel' means the streaming will
be applied via a parallel apply worker, if available. The parameter value
'on' means the streaming transaction will be spilled to disk. The default value
is 'off' (same as current behaviour).

In addition, the patch extends the logical replication STREAM_ABORT message so
that abort_time and abort_lsn can also be sent which can be used to update the
replication origin in parallel apply worker when the streaming transaction is
aborted. Because this message extension is needed to support parallel
streaming, meaning that parallel streaming is not supported for publications on
servers < PG16.
---
 doc/src/sgml/catalogs.sgml                    |   11 +-
 doc/src/sgml/config.sgml                      |   28 +-
 doc/src/sgml/logical-replication.sgml         |   21 +-
 doc/src/sgml/protocol.sgml                    |   29 +-
 doc/src/sgml/ref/create_subscription.sgml     |   24 +-
 src/backend/access/transam/xact.c             |   13 +
 src/backend/commands/define.c                 |   58 +
 src/backend/commands/subscriptioncmds.c       |   10 +-
 src/backend/libpq/pqmq.c                      |   18 +-
 src/backend/postmaster/bgworker.c             |    3 +
 .../libpqwalreceiver/libpqwalreceiver.c       |   12 +-
 src/backend/replication/logical/Makefile      |    1 +
 .../replication/logical/applyparallelworker.c | 1078 +++++++++++++++++
 src/backend/replication/logical/decode.c      |   10 +-
 src/backend/replication/logical/launcher.c    |  167 ++-
 src/backend/replication/logical/proto.c       |   37 +-
 .../replication/logical/reorderbuffer.c       |   10 +-
 src/backend/replication/logical/tablesync.c   |    6 +-
 src/backend/replication/logical/worker.c      |  872 ++++++++++---
 src/backend/replication/pgoutput/pgoutput.c   |   20 +-
 src/backend/storage/ipc/procsignal.c          |    4 +
 src/backend/tcop/postgres.c                   |    3 +
 src/backend/utils/activity/wait_event.c       |    3 +
 src/backend/utils/misc/guc_tables.c           |   12 +
 src/backend/utils/misc/postgresql.conf.sample |    1 +
 src/bin/pg_dump/pg_dump.c                     |    6 +-
 src/include/catalog/pg_subscription.h         |   21 +-
 src/include/commands/defrem.h                 |    1 +
 src/include/nodes/pg_list.h                   |   11 +
 src/include/replication/logicallauncher.h     |    1 +
 src/include/replication/logicalproto.h        |   28 +-
 src/include/replication/logicalworker.h       |    6 +
 src/include/replication/pgoutput.h            |    2 +-
 src/include/replication/reorderbuffer.h       |    7 +-
 src/include/replication/walreceiver.h         |    2 +-
 src/include/replication/worker_internal.h     |  130 +-
 src/include/storage/procsignal.h              |    1 +
 src/include/utils/wait_event.h                |    1 +
 src/test/regress/expected/subscription.out    |   12 +-
 src/test/regress/sql/subscription.sql         |    6 +-
 src/tools/pgindent/typedefs.list              |    5 +
 41 files changed, 2428 insertions(+), 263 deletions(-)
 create mode 100644 src/backend/replication/logical/applyparallelworker.c

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index 00f833d210..c5769da26b 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -7892,11 +7892,16 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
 
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
-       <structfield>substream</structfield> <type>bool</type>
+       <structfield>substream</structfield> <type>char</type>
       </para>
       <para>
-       If true, the subscription will allow streaming of in-progress
-       transactions
+       Controls how to handle the streaming of in-progress transactions:
+       <literal>f</literal> = disallow streaming of in-progress transactions,
+       <literal>t</literal> = spill the changes of in-progress transactions to
+       disk and apply at once after the transaction is committed on the
+       publisher,
+       <literal>p</literal> = apply changes directly using a parallel apply
+       worker if available (same as 't' if no worker is available)
       </para></entry>
      </row>
 
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 700914684d..cb2be8a2e1 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4940,7 +4940,8 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
       <listitem>
        <para>
         Specifies maximum number of logical replication workers. This includes
-        both apply workers and table synchronization workers.
+        leader apply workers, parallel apply workers, and table synchronization
+        workers.
        </para>
        <para>
         Logical replication workers are taken from the pool defined by
@@ -4980,6 +4981,31 @@ ANY <replaceable class="parameter">num_sync</replaceable> ( <replaceable class="
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-max-parallel-apply-workers-per-subscription" xreflabel="max_parallel_apply_workers_per_subscription">
+      <term><varname>max_parallel_apply_workers_per_subscription</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>max_parallel_apply_workers_per_subscription</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        Maximum number of parallel apply workers per subscription. This
+        parameter controls the amount of parallelism for streaming of
+        in-progress transactions with subscription parameter
+        <literal>streaming = parallel</literal>.
+       </para>
+       <para>
+        The parallel apply workers are taken from the pool defined by
+        <varname>max_logical_replication_workers</varname>.
+       </para>
+       <para>
+        The default value is 2. This parameter can only be set in the
+        <filename>postgresql.conf</filename> file or on the server command
+        line.
+       </para>
+      </listitem>
+     </varlistentry>
+
      </variablelist>
     </sect2>
 
diff --git a/doc/src/sgml/logical-replication.sgml b/doc/src/sgml/logical-replication.sgml
index 0ab191e402..6470f40e23 100644
--- a/doc/src/sgml/logical-replication.sgml
+++ b/doc/src/sgml/logical-replication.sgml
@@ -1370,6 +1370,16 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    might not violate any constraint.  This can easily make the subscriber
    inconsistent.
   </para>
+
+  <para>
+   When the streaming mode is <literal>parallel</literal>, the finish LSN of
+   failed transactions may not be logged. In that case, it may be necessary to
+   change the streaming mode to <literal>on</literal> or <literal>off</literal> and
+   cause the same conflicts again so the finish LSN of the failed transaction will
+   be written to the server log. For the usage of finish LSN, please refer to <link
+   linkend="sql-altersubscription"><command>ALTER SUBSCRIPTION ...
+   SKIP</command></link>.
+  </para>
  </sect1>
 
  <sect1 id="logical-replication-restrictions">
@@ -1551,7 +1561,8 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    subscription.  A disabled subscription or a crashed subscription will have
    zero rows in this view.  If the initial data synchronization of any
    table is in progress, there will be additional workers for the tables
-   being synchronized.
+   being synchronized. Moreover, if the streaming transaction is applied in
+   parallel, there will be additional workers.
   </para>
  </sect1>
 
@@ -1646,8 +1657,12 @@ CONTEXT:  processing remote data for replication origin "pg_16395" during "INSER
    to the subscriber, plus some reserve for table synchronization.
    <varname>max_logical_replication_workers</varname> must be set to at least
    the number of subscriptions, again plus some reserve for the table
-   synchronization.  Additionally the <varname>max_worker_processes</varname>
-   may need to be adjusted to accommodate for replication workers, at least
+   synchronization. In addition, if the subscription parameter
+   <literal>streaming</literal> is set to <literal>parallel</literal>, please
+   increase <literal>max_logical_replication_workers</literal> according to
+   the desired number of parallel apply workers.  Additionally the
+   <varname>max_worker_processes</varname> may need to be adjusted to
+   accommodate for replication workers, at least
    (<varname>max_logical_replication_workers</varname>
    + <literal>1</literal>).  Note that some extensions and parallel queries
    also take worker slots from <varname>max_worker_processes</varname>.
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index f63c912e97..2b973c13eb 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -3100,7 +3100,7 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
      <listitem>
       <para>
        Protocol version. Currently versions <literal>1</literal>, <literal>2</literal>,
-       and <literal>3</literal> are supported.
+       <literal>3</literal>, and <literal>4</literal> are supported.
       </para>
       <para>
        Version <literal>2</literal> is supported only for server version 14
@@ -3110,6 +3110,11 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
        Version <literal>3</literal> is supported only for server version 15
        and above, and it allows streaming of two-phase commits.
       </para>
+      <para>
+       Version <literal>4</literal> is supported only for server version 16
+       and above, and it allows applying streams of large in-progress
+       transactions in parallel.
+      </para>
      </listitem>
     </varlistentry>
 
@@ -6880,6 +6885,28 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
         </para>
        </listitem>
       </varlistentry>
+
+      <varlistentry>
+       <term>Int64 (XLogRecPtr)</term>
+       <listitem>
+        <para>
+         The LSN of the abort. This field is available since protocol version
+         4.
+        </para>
+       </listitem>
+      </varlistentry>
+
+      <varlistentry>
+       <term>Int64 (TimestampTz)</term>
+       <listitem>
+        <para>
+         Abort timestamp of the transaction. The value is in number
+         of microseconds since PostgreSQL epoch (2000-01-01). This field is
+         available since protocol version 4.
+        </para>
+       </listitem>
+      </varlistentry>
+
      </variablelist>
     </listitem>
    </varlistentry>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 4e001f8111..175cce8506 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -222,13 +222,29 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
        </varlistentry>
 
        <varlistentry>
-        <term><literal>streaming</literal> (<type>boolean</type>)</term>
+        <term><literal>streaming</literal> (<type>enum</type>)</term>
         <listitem>
          <para>
           Specifies whether to enable streaming of in-progress transactions
-          for this subscription.  By default, all transactions
-          are fully decoded on the publisher and only then sent to the
-          subscriber as a whole.
+          for this subscription.  The default value is <literal>off</literal>,
+          meaning all transactions are fully decoded on the publisher and only
+          then sent to the subscriber as a whole.
+         </para>
+
+         <para>
+          If set to <literal>on</literal>, the incoming changes are written to
+          temporary files and then applied only after the transaction is
+          committed on the publisher and received by the subscriber.
+         </para>
+
+         <para>
+          If set to <literal>parallel</literal>, incoming changes are directly
+          applied via one of the parallel apply workers, if available. If no
+          parallel worker is free to handle streaming transactions then the
+          changes are written to temporary files and applied after the
+          transaction is committed. Note that if an error happens when
+          applying changes in a parallel worker, the finish LSN of the
+          remote transaction might not be reported in the server log.
          </para>
         </listitem>
        </varlistentry>
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 50f092d7eb..5a76d9c1a1 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -1711,6 +1711,7 @@ RecordTransactionAbort(bool isSubXact)
 	int			nchildren;
 	TransactionId *children;
 	TimestampTz xact_time;
+	bool		replorigin;
 
 	/*
 	 * If we haven't been assigned an XID, nobody will care whether we aborted
@@ -1741,6 +1742,13 @@ RecordTransactionAbort(bool isSubXact)
 		elog(PANIC, "cannot abort transaction %u, it was already committed",
 			 xid);
 
+	/*
+	 * Are we using the replication origins feature?  Or, in other words,
+	 * are we replaying remote actions?
+	 */
+	replorigin = (replorigin_session_origin != InvalidRepOriginId &&
+				  replorigin_session_origin != DoNotReplicateId);
+
 	/* Fetch the data we need for the abort record */
 	nrels = smgrGetPendingDeletes(false, &rels);
 	nchildren = xactGetCommittedChildren(&children);
@@ -1765,6 +1773,11 @@ RecordTransactionAbort(bool isSubXact)
 					   MyXactFlags, InvalidTransactionId,
 					   NULL);
 
+	if (replorigin)
+		/* Move LSNs forward for this replication origin */
+		replorigin_session_advance(replorigin_session_origin_lsn,
+								   XactLastRecEnd);
+
 	/*
 	 * Report the latest async abort LSN, so that the WAL writer knows to
 	 * flush this abort. There's nothing to be gained by delaying this, since
diff --git a/src/backend/commands/define.c b/src/backend/commands/define.c
index 86b89071ee..11312d1920 100644
--- a/src/backend/commands/define.c
+++ b/src/backend/commands/define.c
@@ -36,6 +36,7 @@
 #include <math.h>
 
 #include "catalog/namespace.h"
+#include "catalog/pg_subscription.h"
 #include "commands/defrem.h"
 #include "nodes/makefuncs.h"
 #include "parser/parse_type.h"
@@ -345,6 +346,63 @@ defGetStringList(DefElem *def)
 	return (List *) def->arg;
 }
 
+/*
+ * Extract the streaming mode value from a DefElem.  This is like
+ * defGetBoolean() but also accepts the special value of "parallel".
+ */
+char
+defGetStreamingMode(DefElem *def)
+{
+	/*
+	 * If no parameter value given, assume "true" is meant.
+	 */
+	if (def->arg == NULL)
+		return SUBSTREAM_ON;
+
+	/*
+	 * Allow 0, 1, "false", "true", "off", "on" or "parallel".
+	 */
+	switch (nodeTag(def->arg))
+	{
+		case T_Integer:
+			switch (intVal(def->arg))
+			{
+				case 0:
+					return SUBSTREAM_OFF;
+				case 1:
+					return SUBSTREAM_ON;
+				default:
+					/* otherwise, error out below */
+					break;
+			}
+			break;
+		default:
+			{
+				char	   *sval = defGetString(def);
+
+				/*
+				 * The set of strings accepted here should match up with the
+				 * grammar's opt_boolean_or_string production.
+				 */
+				if (pg_strcasecmp(sval, "false") == 0 ||
+					pg_strcasecmp(sval, "off") == 0)
+					return SUBSTREAM_OFF;
+				if (pg_strcasecmp(sval, "true") == 0 ||
+					pg_strcasecmp(sval, "on") == 0)
+					return SUBSTREAM_ON;
+				if (pg_strcasecmp(sval, "parallel") == 0)
+					return SUBSTREAM_PARALLEL;
+			}
+			break;
+	}
+
+	ereport(ERROR,
+			(errcode(ERRCODE_SYNTAX_ERROR),
+			 errmsg("%s requires a Boolean value or \"parallel\"",
+					def->defname)));
+	return SUBSTREAM_OFF;		/* keep compiler quiet */
+}
+
 /*
  * Raise an error about a conflicting DefElem.
  */
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index 1024d51dca..fa5a0cc405 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -84,7 +84,7 @@ typedef struct SubOpts
 	bool		copy_data;
 	bool		refresh;
 	bool		binary;
-	bool		streaming;
+	char		streaming;
 	bool		twophase;
 	bool		disableonerr;
 	char	   *origin;
@@ -138,7 +138,7 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 	if (IsSet(supported_opts, SUBOPT_BINARY))
 		opts->binary = false;
 	if (IsSet(supported_opts, SUBOPT_STREAMING))
-		opts->streaming = false;
+		opts->streaming = SUBSTREAM_OFF;
 	if (IsSet(supported_opts, SUBOPT_TWOPHASE_COMMIT))
 		opts->twophase = false;
 	if (IsSet(supported_opts, SUBOPT_DISABLE_ON_ERR))
@@ -241,7 +241,7 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 				errorConflictingDefElem(defel, pstate);
 
 			opts->specified_opts |= SUBOPT_STREAMING;
-			opts->streaming = defGetBoolean(defel);
+			opts->streaming = defGetStreamingMode(defel);
 		}
 		else if (strcmp(defel->defname, "two_phase") == 0)
 		{
@@ -631,7 +631,7 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 	values[Anum_pg_subscription_subowner - 1] = ObjectIdGetDatum(owner);
 	values[Anum_pg_subscription_subenabled - 1] = BoolGetDatum(opts.enabled);
 	values[Anum_pg_subscription_subbinary - 1] = BoolGetDatum(opts.binary);
-	values[Anum_pg_subscription_substream - 1] = BoolGetDatum(opts.streaming);
+	values[Anum_pg_subscription_substream - 1] = CharGetDatum(opts.streaming);
 	values[Anum_pg_subscription_subtwophasestate - 1] =
 		CharGetDatum(opts.twophase ?
 					 LOGICALREP_TWOPHASE_STATE_PENDING :
@@ -1101,7 +1101,7 @@ AlterSubscription(ParseState *pstate, AlterSubscriptionStmt *stmt,
 				if (IsSet(opts.specified_opts, SUBOPT_STREAMING))
 				{
 					values[Anum_pg_subscription_substream - 1] =
-						BoolGetDatum(opts.streaming);
+						CharGetDatum(opts.streaming);
 					replaces[Anum_pg_subscription_substream - 1] = true;
 				}
 
diff --git a/src/backend/libpq/pqmq.c b/src/backend/libpq/pqmq.c
index 4d0415e379..6d5394e3b1 100644
--- a/src/backend/libpq/pqmq.c
+++ b/src/backend/libpq/pqmq.c
@@ -13,11 +13,13 @@
 
 #include "postgres.h"
 
+#include "access/parallel.h"
 #include "libpq/libpq.h"
 #include "libpq/pqformat.h"
 #include "libpq/pqmq.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "replication/logicalworker.h"
 #include "tcop/tcopprot.h"
 #include "utils/builtins.h"
 
@@ -162,9 +164,19 @@ mq_putmessage(char msgtype, const char *s, size_t len)
 		result = shm_mq_sendv(pq_mq_handle, iov, 2, true, true);
 
 		if (pq_mq_parallel_leader_pid != 0)
-			SendProcSignal(pq_mq_parallel_leader_pid,
-						   PROCSIG_PARALLEL_MESSAGE,
-						   pq_mq_parallel_leader_backend_id);
+		{
+			if (IsParallelWorker())
+				SendProcSignal(pq_mq_parallel_leader_pid,
+							   PROCSIG_PARALLEL_MESSAGE,
+							   pq_mq_parallel_leader_backend_id);
+			else
+			{
+				Assert(IsLogicalParallelApplyWorker());
+				SendProcSignal(pq_mq_parallel_leader_pid,
+							   PROCSIG_PARALLEL_APPLY_MESSAGE,
+							   pq_mq_parallel_leader_backend_id);
+			}
+		}
 
 		if (result != SHM_MQ_WOULD_BLOCK)
 			break;
diff --git a/src/backend/postmaster/bgworker.c b/src/backend/postmaster/bgworker.c
index 40601aefd9..ee481bb21a 100644
--- a/src/backend/postmaster/bgworker.c
+++ b/src/backend/postmaster/bgworker.c
@@ -128,6 +128,9 @@ static const struct
 	},
 	{
 		"ApplyWorkerMain", ApplyWorkerMain
+	},
+	{
+		"ParallelApplyWorkerMain", ParallelApplyWorkerMain
 	}
 };
 
diff --git a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
index 7f697b0f29..dabf4b52d1 100644
--- a/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
+++ b/src/backend/replication/libpqwalreceiver/libpqwalreceiver.c
@@ -20,6 +20,7 @@
 #include <sys/time.h>
 
 #include "access/xlog.h"
+#include "catalog/pg_subscription.h"
 #include "catalog/pg_type.h"
 #include "common/connect.h"
 #include "funcapi.h"
@@ -443,9 +444,14 @@ libpqrcv_startstreaming(WalReceiverConn *conn,
 		appendStringInfo(&cmd, "proto_version '%u'",
 						 options->proto.logical.proto_version);
 
-		if (options->proto.logical.streaming &&
-			PQserverVersion(conn->streamConn) >= 140000)
-			appendStringInfoString(&cmd, ", streaming 'on'");
+		if (options->proto.logical.streaming != SUBSTREAM_OFF)
+		{
+			if (PQserverVersion(conn->streamConn) >= 160000 &&
+				options->proto.logical.streaming == SUBSTREAM_PARALLEL)
+				appendStringInfoString(&cmd, ", streaming 'parallel'");
+			else if (PQserverVersion(conn->streamConn) >= 140000)
+				appendStringInfoString(&cmd, ", streaming 'on'");
+		}
 
 		if (options->proto.logical.twophase &&
 			PQserverVersion(conn->streamConn) >= 150000)
diff --git a/src/backend/replication/logical/Makefile b/src/backend/replication/logical/Makefile
index c4e2fdeb71..2dc25e37bb 100644
--- a/src/backend/replication/logical/Makefile
+++ b/src/backend/replication/logical/Makefile
@@ -15,6 +15,7 @@ include $(top_builddir)/src/Makefile.global
 override CPPFLAGS := -I$(srcdir) $(CPPFLAGS)
 
 OBJS = \
+	applyparallelworker.o \
 	decode.o \
 	launcher.o \
 	logical.o \
diff --git a/src/backend/replication/logical/applyparallelworker.c b/src/backend/replication/logical/applyparallelworker.c
new file mode 100644
index 0000000000..2f771fc4a1
--- /dev/null
+++ b/src/backend/replication/logical/applyparallelworker.c
@@ -0,0 +1,1078 @@
+/*-------------------------------------------------------------------------
+ * applyparallelworker.c
+ *     Support routines for applying xact by parallel apply worker
+ *
+ * Copyright (c) 2016-2022, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/backend/replication/logical/applyparallelworker.c
+ *
+ * This file contains routines that are intended to support setting up, using,
+ * and tearing down a ParallelApplyWorkerInfo.
+ *
+ * Refer to the comments in file header of logical/worker.c to see more
+ * information about parallel apply worker.
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "libpq/pqformat.h"
+#include "libpq/pqmq.h"
+#include "mb/pg_wchar.h"
+#include "pgstat.h"
+#include "postmaster/interrupt.h"
+#include "replication/logicallauncher.h"
+#include "replication/logicalworker.h"
+#include "replication/origin.h"
+#include "replication/walreceiver.h"
+#include "replication/worker_internal.h"
+#include "storage/ipc.h"
+#include "storage/procarray.h"
+#include "tcop/tcopprot.h"
+#include "utils/inval.h"
+#include "utils/memutils.h"
+#include "utils/resowner.h"
+#include "utils/syscache.h"
+
+#define PG_LOGICAL_APPLY_SHM_MAGIC 0x787ca067
+
+/*
+ * DSM keys for parallel apply worker.  Unlike other parallel execution code,
+ * since we don't need to worry about DSM keys conflicting with plan_node_id we
+ * can use small integers.
+ */
+#define PARALLEL_APPLY_KEY_SHARED		1
+#define PARALLEL_APPLY_KEY_MQ			2
+#define PARALLEL_APPLY_KEY_ERROR_QUEUE	3
+
+/* Queue size of DSM, 16 MB for now. */
+#define DSM_QUEUE_SIZE	(16 * 1024 * 1024)
+
+/*
+ * Error queue size of DSM. It is desirable to make it large enough that a
+ * typical ErrorResponse can be sent without blocking.  That way, a worker that
+ * errors out can write the whole message into the queue and terminate without
+ * waiting for the user backend.
+ */
+#define DSM_ERROR_QUEUE_SIZE			(16 * 1024)
+
+/*
+ * There are three fields in each message received by the parallel apply
+ * worker: start_lsn, end_lsn and send_time. Because we have updated these
+ * statistics in the leader apply worker, we can ignore these fields in the
+ * parallel apply worker (see function LogicalRepApplyLoop).
+ */
+#define SIZE_STATS_MESSAGE (2 * sizeof(XLogRecPtr) + sizeof(TimestampTz))
+
+/*
+ * Hash table entry to map xid to the parallel apply worker state.
+ */
+typedef struct ParallelApplyWorkerEntry
+{
+	TransactionId xid;	/* Hash key -- must be first */
+	ParallelApplyWorkerInfo *winfo;
+} ParallelApplyWorkerEntry;
+
+/* Parallel apply workers hash table (initialized on first use). */
+static HTAB *ParallelApplyWorkersHash = NULL;
+
+/*
+ * A list to maintain the active parallel apply workers. The information for
+ * the new worker is added to the list after successfully launching it. The
+ * list entry is removed at the end of the transaction if there are already
+ * enough workers in the worker pool. For more information about the worker
+ * pool, see comments atop worker.c. We also remove the entry from the list if
+ * the worker is exited due to some error.
+ */
+static List *ParallelApplyWorkersList = NIL;
+
+/*
+ * Information shared between leader apply worker and parallel apply worker.
+ */
+ParallelApplyWorkerShared *MyParallelShared = NULL;
+
+/*
+ * Is there a message pending in parallel apply worker which we need to
+ * receive?
+ */
+volatile bool ParallelApplyMessagePending = false;
+
+/*
+ * Cache the parallel apply worker information required for applying the
+ * current streaming transaction. It is used to save the cost of searching the
+ * hash table when applying the changes between STREAM_START and STREAM_STOP.
+ */
+ParallelApplyWorkerInfo *stream_apply_worker = NULL;
+
+/* A list to maintain subtransactions, if any. */
+List	   *subxactlist = NIL;
+
+static bool parallel_apply_can_start(TransactionId xid);
+static bool parallel_apply_setup_dsm(ParallelApplyWorkerInfo *winfo);
+static ParallelApplyWorkerInfo *parallel_apply_setup_worker(void);
+static bool parallel_apply_get_in_xact(ParallelApplyWorkerShared *wshared);
+
+/*
+ * Returns true, if it is allowed to start a parallel apply worker, false,
+ * otherwise.
+ */
+static bool
+parallel_apply_can_start(TransactionId xid)
+{
+	if (!TransactionIdIsValid(xid))
+		return false;
+
+	/*
+	 * Don't start a new parallel worker if not in parallel streaming mode.
+	 */
+	if (MySubscription->stream != SUBSTREAM_PARALLEL)
+		return false;
+
+	/* Only leader apply workers can start parallel apply workers. */
+	if (am_parallel_apply_worker())
+		return false;
+
+	/*
+	 * Don't start a new parallel worker if user has set skiplsn as it's
+	 * possible that user want to skip the streaming transaction. For
+	 * streaming transaction, we need to spill the transaction to disk so that
+	 * we can get the last LSN of the transaction to judge whether to skip
+	 * before starting to apply the change.
+	 */
+	if (!XLogRecPtrIsInvalid(MySubscription->skiplsn))
+		return false;
+
+	/*
+	 * For streaming transactions that are being applied using a parallel apply
+	 * worker, we cannot decide whether to apply the change for a relation that
+	 * is not in the READY state (see should_apply_changes_for_rel) as we won't
+	 * know remote_final_lsn by that time. So, we don't start the new parallel
+	 * apply worker in this case.
+	 */
+	if (!AllTablesyncsReady())
+		return false;
+
+	/*
+	 * Parallel apply is not supported when subscribing to a publisher which
+	 * cannot provide the abort_time and abort_lsn.
+	 */
+	if (walrcv_server_version(LogRepWorkerWalRcvConn) < 160000)
+		return false;
+
+	return true;
+}
+
+/*
+ * Start a parallel apply worker that will be used for the specified xid.
+ *
+ * If a parallel apply worker is found but not in use then re-use it, otherwise
+ * start a fresh one. Cache the worker information in ParallelApplyWorkersHash
+ * keyed by the specified xid.
+ */
+void
+parallel_apply_start_worker(TransactionId xid)
+{
+	bool		found;
+	ListCell   *lc;
+	ParallelApplyWorkerInfo *winfo = NULL;
+	ParallelApplyWorkerEntry *entry = NULL;
+
+	if (!parallel_apply_can_start(xid))
+		return;
+
+	/* First time through, initialize apply workers hashtable. */
+	if (ParallelApplyWorkersHash == NULL)
+	{
+		HASHCTL		ctl;
+
+		MemSet(&ctl, 0, sizeof(ctl));
+		ctl.keysize = sizeof(TransactionId);
+		ctl.entrysize = sizeof(ParallelApplyWorkerEntry);
+		ctl.hcxt = ApplyContext;
+
+		ParallelApplyWorkersHash = hash_create("logical apply workers hash",
+											   16, &ctl,
+											   HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
+	}
+
+	/* Try to get a free parallel apply worker. */
+	foreach(lc, ParallelApplyWorkersList)
+	{
+		ParallelApplyWorkerInfo *tmp_winfo;
+
+		tmp_winfo = (ParallelApplyWorkerInfo *) lfirst(lc);
+
+		if (tmp_winfo->error_mq_handle == NULL)
+		{
+			/*
+			 * Release the worker information and try next one if the parallel
+			 * apply worker exited cleanly.
+			 */
+			ParallelApplyWorkersList = foreach_delete_current(ParallelApplyWorkersList, lc);
+			shm_mq_detach(tmp_winfo->mq_handle);
+			dsm_detach(tmp_winfo->dsm_seg);
+			pfree(tmp_winfo);
+		}
+		else if (!tmp_winfo->in_use)
+		{
+			/* Found a worker that has not been assigned a transaction. */
+			winfo = tmp_winfo;
+			break;
+		}
+	}
+
+	/* Try to start a new parallel apply worker. */
+	if (winfo == NULL)
+		winfo = parallel_apply_setup_worker();
+
+	/* Failed to start a new parallel apply worker. */
+	if (winfo == NULL)
+		return;
+
+	/* Create entry for requested transaction. */
+	entry = hash_search(ParallelApplyWorkersHash, &xid, HASH_ENTER, &found);
+	if (found)
+		elog(ERROR, "hash table corrupted");
+
+	/*
+	 * Set the in_parallel_apply_xact flag in the leader instead of the
+	 * parallel apply worker to avoid the race condition where the leader has
+	 * already started waiting for the parallel apply worker to finish
+	 * processing the transaction while the child process has not yet processed
+	 * the first STREAM_START and has not set the in_parallel_apply_xact to
+	 * true.
+	 */
+	parallel_apply_set_in_xact(winfo->shared, true);
+
+	winfo->in_use = true;
+	entry->winfo = winfo;
+	entry->xid = xid;
+}
+
+/*
+ * Find the previously assigned worker for the given transaction, if any.
+ */
+ParallelApplyWorkerInfo *
+parallel_apply_find_worker(TransactionId xid)
+{
+	bool		found;
+	ParallelApplyWorkerEntry *entry = NULL;
+
+	if (!TransactionIdIsValid(xid))
+		return NULL;
+
+	if (ParallelApplyWorkersHash == NULL)
+		return NULL;
+
+	/* Return the cached parallel apply worker if valid. */
+	if (stream_apply_worker != NULL)
+		return stream_apply_worker;
+
+	/*
+	 * Find entry for requested transaction.
+	 */
+	entry = hash_search(ParallelApplyWorkersHash, &xid, HASH_FIND, &found);
+	if (found)
+	{
+		/* If any workers (or the postmaster) have died, we have failed. */
+		if (entry->winfo->error_mq_handle == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("lost connection to parallel apply worker")));
+
+		Assert(parallel_apply_get_in_xact(entry->winfo->shared));
+		Assert(entry->winfo->in_use);
+
+		return entry->winfo;
+	}
+
+	return NULL;
+}
+
+/*
+ * Remove the parallel apply worker entry from the hash table. And stop the
+ * worker if there are enough workers in the pool.
+ */
+void
+parallel_apply_free_worker(ParallelApplyWorkerInfo *winfo, TransactionId xid)
+{
+	int			napplyworkers;
+
+	Assert(!am_parallel_apply_worker());
+	Assert(!parallel_apply_get_in_xact(winfo->shared));
+
+	if (!hash_search(ParallelApplyWorkersHash, &xid, HASH_REMOVE, NULL))
+		elog(ERROR, "hash table corrupted");
+
+	LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+	napplyworkers = logicalrep_parallel_apply_worker_count(MyLogicalRepWorker->subid);
+	LWLockRelease(LogicalRepWorkerLock);
+
+	winfo->in_use = false;
+
+	/* Are there enough workers in the pool? */
+	if (napplyworkers > (max_parallel_apply_workers_per_subscription / 2))
+	{
+		logicalrep_worker_stop_by_slot(winfo->shared->logicalrep_worker_slot_no,
+									   winfo->shared->logicalrep_worker_generation);
+
+		ParallelApplyWorkersList = list_delete_ptr(ParallelApplyWorkersList, winfo);
+
+		shm_mq_detach(winfo->mq_handle);
+		shm_mq_detach(winfo->error_mq_handle);
+		dsm_detach(winfo->dsm_seg);
+		pfree(winfo);
+	}
+}
+
+/* Parallel apply worker main loop. */
+static void
+LogicalParallelApplyLoop(shm_mq_handle *mqh, volatile ParallelApplyWorkerShared *shared)
+{
+	shm_mq_result shmq_res;
+	PGPROC	   *registrant;
+	ErrorContextCallback errcallback;
+
+	registrant = BackendPidGetProc(MyBgworkerEntry->bgw_notify_pid);
+	SetLatch(&registrant->procLatch);
+
+	/*
+	 * Init the ApplyMessageContext which we clean up after each replication
+	 * protocol message.
+	 */
+	ApplyMessageContext = AllocSetContextCreate(ApplyContext,
+												"ApplyMessageContext",
+												ALLOCSET_DEFAULT_SIZES);
+
+	/*
+	 * Push apply error context callback. Fields will be filled while applying
+	 * a change.
+	 */
+	errcallback.callback = apply_error_callback;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	for (;;)
+	{
+		void	   *data;
+		Size		len;
+		int			c;
+		StringInfoData s;
+		MemoryContext oldctx;
+
+		CHECK_FOR_INTERRUPTS();
+
+		/* Ensure we are reading the data into our memory context. */
+		oldctx = MemoryContextSwitchTo(ApplyMessageContext);
+
+		shmq_res = shm_mq_receive(mqh, &len, &data, false);
+
+		if (shmq_res != SHM_MQ_SUCCESS)
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("lost connection to the leader apply worker")));
+
+		if (len == 0)
+			break;
+
+		s.cursor = 0;
+		s.maxlen = -1;
+		s.data = (char *) data;
+		s.len = len;
+
+		/*
+		 * The first byte of message for additional communication between
+		 * leader apply worker and parallel apply workers can only be 'w'.
+		 */
+		c = pq_getmsgbyte(&s);
+		if (c != 'w')
+			elog(ERROR, "unexpected message \"%c\"", c);
+
+		/*
+		 * Ignore statistics fields that have been updated by the leader apply
+		 * worker.
+		 */
+		s.cursor += SIZE_STATS_MESSAGE;
+
+		apply_dispatch(&s);
+
+		MemoryContextSwitchTo(oldctx);
+		MemoryContextReset(ApplyMessageContext);
+
+		if (ConfigReloadPending)
+		{
+			ConfigReloadPending = false;
+			ProcessConfigFile(PGC_SIGHUP);
+		}
+	}
+
+	/* Pop the error context stack. */
+	error_context_stack = errcallback.previous;
+
+	/* Signal main process that we are done. */
+	SetLatch(&registrant->procLatch);
+}
+
+/*
+ * Make sure the leader apply worker tries to read from our error queue one more
+ * time. This guards against the case where we exit uncleanly without sending
+ * an ErrorResponse, for example because some code calls proc_exit directly.
+ */
+static void
+parallel_apply_shutdown(int code, Datum arg)
+{
+	SendProcSignal(MyLogicalRepWorker->apply_leader_pid,
+				   PROCSIG_PARALLEL_APPLY_MESSAGE,
+				   InvalidBackendId);
+
+	dsm_detach((dsm_segment *) DatumGetPointer(arg));
+}
+
+/*
+ * Parallel apply worker entry point.
+ */
+void
+ParallelApplyWorkerMain(Datum main_arg)
+{
+	ParallelApplyWorkerShared *shared;
+	dsm_handle	handle;
+	dsm_segment *seg;
+	shm_toc    *toc;
+	shm_mq	   *mq;
+	shm_mq_handle *mqh;
+	shm_mq_handle *error_mqh;
+	int			worker_slot = DatumGetInt32(main_arg);
+	char		originname[NAMEDATALEN];
+
+	/* Setup signal handling. */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
+	pqsignal(SIGTERM, die);
+	BackgroundWorkerUnblockSignals();
+
+	/*
+	 * Attach to the dynamic shared memory segment for the parallel apply, and
+	 * find its table of contents.
+	 *
+	 * Like parallel query, we don't need resource owner by this time. See
+	 * ParallelWorkerMain.
+	 */
+	memcpy(&handle, MyBgworkerEntry->bgw_extra, sizeof(dsm_handle));
+	seg = dsm_attach(handle);
+	if (seg == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("unable to map dynamic shared memory segment")));
+
+	toc = shm_toc_attach(PG_LOGICAL_APPLY_SHM_MAGIC, dsm_segment_address(seg));
+	if (toc == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("bad magic number in dynamic shared memory segment")));
+
+	before_shmem_exit(parallel_apply_shutdown, PointerGetDatum(seg));
+
+	/* Look up the shared information. */
+	shared = shm_toc_lookup(toc, PARALLEL_APPLY_KEY_SHARED, false);
+	MyParallelShared = shared;
+
+	/*
+	 * Attach to the message queue.
+	 */
+	mq = shm_toc_lookup(toc, PARALLEL_APPLY_KEY_MQ, false);
+	shm_mq_set_receiver(mq, MyProc);
+	mqh = shm_mq_attach(mq, seg, NULL);
+
+	/*
+	 * Primary initialization is complete. Now, we can attach to our slot. This
+	 * is to ensure that the leader apply worker does not write data to the
+	 * uninitialized memory queue.
+	 */
+	logicalrep_worker_attach(worker_slot);
+	MyParallelShared->logicalrep_worker_generation = MyLogicalRepWorker->generation;
+	MyParallelShared->logicalrep_worker_slot_no = worker_slot;
+
+	/*
+	 * Attach to the error queue.
+	 */
+	mq = shm_toc_lookup(toc, PARALLEL_APPLY_KEY_ERROR_QUEUE, false);
+	shm_mq_set_sender(mq, MyProc);
+	error_mqh = shm_mq_attach(mq, seg, NULL);
+
+	pq_redirect_to_shm_mq(seg, error_mqh);
+	pq_set_parallel_leader(MyLogicalRepWorker->apply_leader_pid,
+						   InvalidBackendId);
+
+	MyLogicalRepWorker->last_send_time = MyLogicalRepWorker->last_recv_time =
+		MyLogicalRepWorker->reply_time = 0;
+
+	InitializeApplyWorker();
+
+	/*
+	 * Setup callback for syscache so that we know when something changes in
+	 * the subscription relation state.
+	 */
+	CacheRegisterSyscacheCallback(SUBSCRIPTIONRELMAP,
+								  invalidate_syncing_table_states,
+								  (Datum) 0);
+
+	/*
+	 * Allocate the origin name in long-lived context for error context
+	 * message.
+	 */
+	snprintf(originname, sizeof(originname), "pg_%u", MySubscription->oid);
+	apply_error_callback_arg.origin_name = MemoryContextStrdup(ApplyContext,
+															   originname);
+
+	LogicalParallelApplyLoop(mqh, shared);
+
+	proc_exit(0);
+}
+
+/*
+ * Handle receipt of an interrupt indicating a parallel apply worker message.
+ *
+ * Note: this is called within a signal handler!  All we can do is set a flag
+ * that will cause the next CHECK_FOR_INTERRUPTS() to invoke
+ * HandleParallelApplyMessages().
+ */
+void
+HandleParallelApplyMessageInterrupt(void)
+{
+	InterruptPending = true;
+	ParallelApplyMessagePending = true;
+	SetLatch(MyLatch);
+}
+
+/*
+ * Handle a single protocol message received from a single parallel apply
+ * worker.
+ */
+static void
+HandleParallelApplyMessage(ParallelApplyWorkerInfo *winfo, StringInfo msg)
+{
+	char		msgtype;
+
+	msgtype = pq_getmsgbyte(msg);
+
+	switch (msgtype)
+	{
+		case 'E':				/* ErrorResponse */
+			{
+				ErrorData	edata;
+				ErrorContextCallback *save_error_context_stack;
+
+				/* Parse ErrorResponse. */
+				pq_parse_errornotice(msg, &edata);
+
+				/* Death of a worker isn't enough justification for suicide. */
+				edata.elevel = Min(edata.elevel, ERROR);
+
+				/*
+				 * If desired, add a context line to show that this is a
+				 * message propagated from a parallel apply worker.
+				 * Otherwise, it can sometimes be confusing to understand what
+				 * actually happened.
+				 */
+				if (edata.context)
+					edata.context = psprintf("%s\n%s", edata.context,
+											 _("parallel apply worker"));
+				else
+					edata.context = pstrdup(_("parallel apply worker"));
+
+				/*
+				 * Context beyond that should use the error context callbacks
+				 * that were in effect in LogicalRepApplyLoop().
+				 */
+				save_error_context_stack = error_context_stack;
+				error_context_stack = apply_error_context_stack;
+
+				ThrowErrorData(&edata);
+
+				/* Should not reach here after rethrowing an error. */
+				error_context_stack = save_error_context_stack;
+
+				break;
+			}
+
+		case 'X':				/* Terminate, indicating clean exit */
+			{
+				shm_mq_detach(winfo->error_mq_handle);
+				winfo->error_mq_handle = NULL;
+				break;
+			}
+
+			/*
+			 * Don't need to do anything about NoticeResponse and
+			 * NotifyResponse as the logical replication worker doesn't need to
+			 * send messages to the client.
+			 */
+		case 'N':
+		case 'A':
+				break;
+		default:
+			{
+				elog(ERROR, "unrecognized message type received from parallel apply worker: %c (message length %d bytes)",
+					 msgtype, msg->len);
+			}
+	}
+}
+
+/*
+ * Handle any queued protocol messages received from parallel apply workers.
+ */
+void
+HandleParallelApplyMessages(void)
+{
+	ListCell	 *lc;
+	MemoryContext oldcontext;
+
+	static MemoryContext hpm_context = NULL;
+
+	/*
+	 * This is invoked from ProcessInterrupts(), and since some of the
+	 * functions it calls contain CHECK_FOR_INTERRUPTS(), there is a potential
+	 * for recursive calls if more signals are received while this runs.  It's
+	 * unclear that recursive entry would be safe, and it doesn't seem useful
+	 * even if it is safe, so let's block interrupts until done.
+	 */
+	HOLD_INTERRUPTS();
+
+	/*
+	 * Moreover, CurrentMemoryContext might be pointing almost anywhere.  We
+	 * don't want to risk leaking data into long-lived contexts, so let's do
+	 * our work here in a private context that we can reset on each use.
+	 */
+	if (hpm_context == NULL)	/* first time through? */
+		hpm_context = AllocSetContextCreate(TopMemoryContext,
+											"HandleParallelApplyMessages",
+											ALLOCSET_DEFAULT_SIZES);
+	else
+		MemoryContextReset(hpm_context);
+
+	oldcontext = MemoryContextSwitchTo(hpm_context);
+
+	ParallelApplyMessagePending = false;
+
+	foreach(lc, ParallelApplyWorkersList)
+	{
+		shm_mq_result res;
+		Size		nbytes;
+		void	   *data;
+		ParallelApplyWorkerInfo *winfo = (ParallelApplyWorkerInfo *) lfirst(lc);
+
+		if (winfo->error_mq_handle == NULL)
+			continue;
+
+		res = shm_mq_receive(winfo->error_mq_handle, &nbytes,
+							 &data, true);
+
+		if (res == SHM_MQ_WOULD_BLOCK)
+			break;
+		else if (res == SHM_MQ_SUCCESS)
+		{
+			StringInfoData msg;
+
+			initStringInfo(&msg);
+			appendBinaryStringInfo(&msg, data, nbytes);
+			HandleParallelApplyMessage(winfo, &msg);
+			pfree(msg.data);
+		}
+		else
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("lost connection to the leader apply worker")));
+	}
+
+	MemoryContextSwitchTo(oldcontext);
+
+	/* Might as well clear the context on our way out */
+	MemoryContextReset(hpm_context);
+
+	RESUME_INTERRUPTS();
+}
+
+/*
+ * Set up a dynamic shared memory segment.
+ *
+ * We set up a control region that contains a ParallelApplyWorkerShared, plus
+ * one region to each of message queue and error queue.
+ *
+ * Returns true on success, false on failure.
+ */
+static bool
+parallel_apply_setup_dsm(ParallelApplyWorkerInfo *winfo)
+{
+	shm_toc_estimator e;
+	Size		segsize;
+	dsm_segment *seg;
+	shm_toc    *toc;
+	ParallelApplyWorkerShared *shared;
+	shm_mq	   *mq;
+	Size		queue_size = DSM_QUEUE_SIZE;
+	Size		error_queue_size = DSM_ERROR_QUEUE_SIZE;
+
+	/*
+	 * Estimate how much shared memory we need.
+	 *
+	 * Because the TOC machinery may choose to insert padding of oddly-sized
+	 * requests, we must estimate each chunk separately.
+	 *
+	 * We need one key to register the location of the header, and we need
+	 * another key to track the location of the message queue.
+	 */
+	shm_toc_initialize_estimator(&e);
+	shm_toc_estimate_chunk(&e, sizeof(ParallelApplyWorkerShared));
+	shm_toc_estimate_chunk(&e, queue_size);
+	shm_toc_estimate_chunk(&e, error_queue_size);
+
+	shm_toc_estimate_keys(&e, 3);
+	segsize = shm_toc_estimate(&e);
+
+	/* Create the shared memory segment and establish a table of contents. */
+	seg = dsm_create(shm_toc_estimate(&e), 0);
+	if (seg == NULL)
+		return false;
+
+	toc = shm_toc_create(PG_LOGICAL_APPLY_SHM_MAGIC, dsm_segment_address(seg),
+						 segsize);
+
+	/* Set up the header region. */
+	shared = shm_toc_allocate(toc, sizeof(ParallelApplyWorkerShared));
+	SpinLockInit(&shared->mutex);
+
+	shared->in_parallel_apply_xact = false;
+
+	shm_toc_insert(toc, PARALLEL_APPLY_KEY_SHARED, shared);
+
+	/* Set up message queue for the worker. */
+	mq = shm_mq_create(shm_toc_allocate(toc, queue_size), queue_size);
+	shm_toc_insert(toc, PARALLEL_APPLY_KEY_MQ, mq);
+	shm_mq_set_sender(mq, MyProc);
+
+	/* Attach the queue. */
+	winfo->mq_handle = shm_mq_attach(mq, seg, NULL);
+
+	/* Set up error queue for the worker. */
+	mq = shm_mq_create(shm_toc_allocate(toc, error_queue_size),
+					   error_queue_size);
+	shm_toc_insert(toc, PARALLEL_APPLY_KEY_ERROR_QUEUE, mq);
+	shm_mq_set_receiver(mq, MyProc);
+
+	/* Attach the queue. */
+	winfo->error_mq_handle = shm_mq_attach(mq, seg, NULL);
+
+	/* Return results to caller. */
+	winfo->dsm_seg = seg;
+	winfo->shared = shared;
+
+	return true;
+}
+
+/*
+ * Start parallel apply worker process and allocate shared memory for it.
+ */
+static ParallelApplyWorkerInfo *
+parallel_apply_setup_worker(void)
+{
+	MemoryContext oldcontext;
+	bool		launched;
+	ParallelApplyWorkerInfo *winfo;
+
+	oldcontext = MemoryContextSwitchTo(ApplyContext);
+
+	winfo = (ParallelApplyWorkerInfo *) palloc0(sizeof(ParallelApplyWorkerInfo));
+
+	/* Setup shared memory. */
+	if (!parallel_apply_setup_dsm(winfo))
+	{
+		MemoryContextSwitchTo(oldcontext);
+		pfree(winfo);
+
+		return NULL;
+	}
+
+	launched = logicalrep_worker_launch(MyLogicalRepWorker->dbid,
+										MySubscription->oid,
+										MySubscription->name,
+										MyLogicalRepWorker->userid,
+										InvalidOid,
+										dsm_segment_handle(winfo->dsm_seg));
+
+	if (launched)
+		ParallelApplyWorkersList = lappend(ParallelApplyWorkersList, winfo);
+	else
+	{
+		shm_mq_detach(winfo->mq_handle);
+		shm_mq_detach(winfo->error_mq_handle);
+		dsm_detach(winfo->dsm_seg);
+		pfree(winfo);
+
+		winfo = NULL;
+	}
+
+	MemoryContextSwitchTo(oldcontext);
+
+	return winfo;
+}
+
+/*
+ * Send the data to the specified parallel apply worker via shared-memory queue.
+ */
+void
+parallel_apply_send_data(ParallelApplyWorkerInfo *winfo, Size nbytes,
+						 const void *data)
+{
+	shm_mq_result result;
+
+	result = shm_mq_send(winfo->mq_handle, nbytes, data, false, true);
+
+	if (result != SHM_MQ_SUCCESS)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("could not send data to shared-memory queue")));
+}
+
+/*
+ * Wait until the parallel apply worker processed the transaction finish command.
+ */
+void
+parallel_apply_wait_for_xact_finish(ParallelApplyWorkerInfo *winfo)
+{
+	for (;;)
+	{
+		if (!parallel_apply_get_in_xact(winfo->shared))
+			break;
+
+		/* If any workers have died, we have failed. */
+		if (winfo->error_mq_handle == NULL)
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("lost connection to parallel apply worker")));
+
+		/* Wait to be signalled. */
+		(void) WaitLatch(MyLatch,
+						 WL_LATCH_SET | WL_TIMEOUT | WL_EXIT_ON_PM_DEATH,
+						 1000L,
+						 WAIT_EVENT_LOGICAL_PARALLEL_APPLY_STATE_CHANGE);
+
+		/* Reset the latch so we don't spin. */
+		ResetLatch(MyLatch);
+
+		/* An interrupt may have occurred while we were waiting. */
+		CHECK_FOR_INTERRUPTS();
+	}
+}
+
+/*
+ * Set the in_parallel_apply_xact flag for the given parallel apply worker.
+ */
+void
+parallel_apply_set_in_xact(ParallelApplyWorkerShared *wshared,
+						   bool in_xact)
+{
+	SpinLockAcquire(&wshared->mutex);
+	wshared->in_parallel_apply_xact = in_xact;
+	SpinLockRelease(&wshared->mutex);
+}
+
+/*
+ * Get the in_parallel_apply_xact flag for the given parallel apply worker.
+ */
+static bool
+parallel_apply_get_in_xact(ParallelApplyWorkerShared *wshared)
+{
+	bool in_xact;
+
+	SpinLockAcquire(&wshared->mutex);
+	in_xact = wshared->in_parallel_apply_xact;
+	SpinLockRelease(&wshared->mutex);
+
+	return in_xact;
+}
+
+/*
+ * Define a savepoint for a subxact in parallel apply worker if needed.
+ *
+ * The parallel apply worker can figure out if a new subtransaction was
+ * started by checking if the new change arrived with different xid. In that
+ * case define a named savepoint, so that we are able to commit/rollback it
+ * separately later.
+ */
+void
+parallel_apply_subxact_info_add(TransactionId current_xid)
+{
+	if (current_xid != stream_xid &&
+		!list_member_xid(subxactlist, current_xid))
+	{
+		MemoryContext oldctx;
+		char		spname[MAXPGPATH];
+
+		parallel_apply_savepoint_name(MySubscription->oid, current_xid,
+									  spname, sizeof(spname));
+
+		elog(DEBUG1, "defining savepoint %s in parallel apply worker", spname);
+
+		/* We must be in transaction block to define the SAVEPOINT. */
+		if (!IsTransactionBlock())
+		{
+			BeginTransactionBlock();
+			CommitTransactionCommand();
+		}
+
+		DefineSavepoint(spname);
+
+		/*
+		 * CommitTransactionCommand is needed to start a subtransaction after
+		 * issuing a SAVEPOINT inside a transaction block (see
+		 * StartSubTransaction()).
+		 */
+		CommitTransactionCommand();
+
+		oldctx = MemoryContextSwitchTo(ApplyContext);
+		subxactlist = lappend_xid(subxactlist, current_xid);
+		MemoryContextSwitchTo(oldctx);
+	}
+}
+
+/*
+ * Handle STREAM ABORT message when the transaction was applied in a parallel
+ * apply worker.
+ */
+void
+parallel_apply_stream_abort(LogicalRepStreamAbortData *abort_data)
+{
+	TransactionId xid = abort_data->xid;
+	TransactionId subxid = abort_data->subxid;
+
+	/*
+	 * Update origin state so we can restart streaming from correct
+	 * position in case of crash.
+	 */
+	replorigin_session_origin_lsn = abort_data->abort_lsn;
+	replorigin_session_origin_timestamp = abort_data->abort_time;
+
+	/*
+	 * If the two XIDs are the same, it's in fact abort of toplevel xact,
+	 * so just free the subxactlist.
+	 */
+	if (subxid == xid)
+	{
+		parallel_apply_replorigin_setup();
+
+		AbortCurrentTransaction();
+
+		if (IsTransactionBlock())
+		{
+			EndTransactionBlock(false);
+			CommitTransactionCommand();
+		}
+
+		parallel_apply_replorigin_reset();
+
+		in_remote_transaction = false;
+		pgstat_report_activity(STATE_IDLE, NULL);
+
+		list_free(subxactlist);
+		subxactlist = NIL;
+	}
+	else
+	{
+		/*
+		 * OK, so it's a subxact. Rollback to the savepoint.
+		 *
+		 * We also need to read the subxactlist, determine the offset
+		 * tracked for the subxact, and truncate the list.
+		 */
+		int			i;
+		bool		found = false;
+		char		spname[MAXPGPATH];
+
+		parallel_apply_savepoint_name(MySubscription->oid, subxid, spname,
+									  sizeof(spname));
+
+		elog(DEBUG1, "rolling back to savepoint %s in parallel apply worker", spname);
+
+		for (i = list_length(subxactlist) - 1; i >= 0; i--)
+		{
+			TransactionId xid_tmp = list_nth_xid(subxactlist, i);
+
+			if (xid_tmp == subxid)
+			{
+				found = true;
+				break;
+			}
+		}
+
+		if (found)
+		{
+			RollbackToSavepoint(spname);
+			CommitTransactionCommand();
+			subxactlist = list_truncate(subxactlist, i + 1);
+		}
+
+		pgstat_report_activity(STATE_IDLEINTRANSACTION, NULL);
+	}
+
+	parallel_apply_set_in_xact(MyParallelShared, false);
+}
+
+/*
+ * Form the savepoint name for the streaming transaction.
+ *
+ * Return the name in the supplied buffer.
+ */
+void
+parallel_apply_savepoint_name(Oid suboid, TransactionId xid,
+							  char *spname, int szsp)
+{
+	snprintf(spname, szsp, "pg_sp_%u_%u", suboid, xid);
+}
+
+/* Setup replication origin tracking. */
+void
+parallel_apply_replorigin_setup(void)
+{
+	RepOriginId originid;
+	char		originname[NAMEDATALEN];
+	bool		started_tx = false;
+
+	/* This function might be called inside or outside of transaction. */
+	if (!IsTransactionState())
+	{
+		StartTransactionCommand();
+		started_tx = true;
+	}
+
+	snprintf(originname, sizeof(originname), "pg_%u", MySubscription->oid);
+	originid = replorigin_by_name(originname, false);
+	replorigin_session_setup(originid);
+	replorigin_session_origin = originid;
+
+	if (started_tx)
+		CommitTransactionCommand();
+}
+
+/* Reset replication origin tracking. */
+void
+parallel_apply_replorigin_reset(void)
+{
+	bool		started_tx = false;
+
+	/* This function might be called inside or outside of transaction. */
+	if (!IsTransactionState())
+	{
+		StartTransactionCommand();
+		started_tx = true;
+	}
+
+	replorigin_session_reset();
+
+	replorigin_session_origin = InvalidRepOriginId;
+	replorigin_session_origin_lsn = InvalidXLogRecPtr;
+	replorigin_session_origin_timestamp = 0;
+
+	if (started_tx)
+		CommitTransactionCommand();
+}
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index 1667d720b1..a4376837e8 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -652,9 +652,10 @@ DecodeCommit(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 	{
 		for (i = 0; i < parsed->nsubxacts; i++)
 		{
-			ReorderBufferForget(ctx->reorder, parsed->subxacts[i], buf->origptr);
+			ReorderBufferForget(ctx->reorder, parsed->subxacts[i], buf->origptr,
+								commit_time);
 		}
-		ReorderBufferForget(ctx->reorder, xid, buf->origptr);
+		ReorderBufferForget(ctx->reorder, xid, buf->origptr, commit_time);
 
 		return;
 	}
@@ -822,10 +823,11 @@ DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 		for (i = 0; i < parsed->nsubxacts; i++)
 		{
 			ReorderBufferAbort(ctx->reorder, parsed->subxacts[i],
-							   buf->record->EndRecPtr);
+							   buf->record->EndRecPtr, abort_time);
 		}
 
-		ReorderBufferAbort(ctx->reorder, xid, buf->record->EndRecPtr);
+		ReorderBufferAbort(ctx->reorder, xid, buf->record->EndRecPtr,
+						   abort_time);
 	}
 
 	/* update the decoding stats */
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index 3bbd522724..8344e4509b 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -54,6 +54,7 @@
 
 int			max_logical_replication_workers = 4;
 int			max_sync_workers_per_subscription = 2;
+int			max_parallel_apply_workers_per_subscription = 2;
 
 LogicalRepWorker *MyLogicalRepWorker = NULL;
 
@@ -73,6 +74,7 @@ static void logicalrep_launcher_onexit(int code, Datum arg);
 static void logicalrep_worker_onexit(int code, Datum arg);
 static void logicalrep_worker_detach(void);
 static void logicalrep_worker_cleanup(LogicalRepWorker *worker);
+static void logicalrep_worker_stop_internal(LogicalRepWorker *worker);
 
 static bool on_commit_launcher_wakeup = false;
 
@@ -151,8 +153,10 @@ get_subscription_list(void)
  *
  * This is only needed for cleaning up the shared memory in case the worker
  * fails to attach.
+ *
+ * Return whether the attach was successful.
  */
-static void
+static bool
 WaitForReplicationWorkerAttach(LogicalRepWorker *worker,
 							   uint16 generation,
 							   BackgroundWorkerHandle *handle)
@@ -168,11 +172,11 @@ WaitForReplicationWorkerAttach(LogicalRepWorker *worker,
 
 		LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
 
-		/* Worker either died or has started; no need to do anything. */
+		/* Worker either died or has started. Return false if died. */
 		if (!worker->in_use || worker->proc)
 		{
 			LWLockRelease(LogicalRepWorkerLock);
-			return;
+			return worker->in_use;
 		}
 
 		LWLockRelease(LogicalRepWorkerLock);
@@ -187,7 +191,7 @@ WaitForReplicationWorkerAttach(LogicalRepWorker *worker,
 			if (generation == worker->generation)
 				logicalrep_worker_cleanup(worker);
 			LWLockRelease(LogicalRepWorkerLock);
-			return;
+			return false;
 		}
 
 		/*
@@ -209,6 +213,8 @@ WaitForReplicationWorkerAttach(LogicalRepWorker *worker,
 /*
  * Walks the workers array and searches for one that matches given
  * subscription id and relid.
+ *
+ * We are only interested in the leader apply worker or table sync worker.
  */
 LogicalRepWorker *
 logicalrep_worker_find(Oid subid, Oid relid, bool only_running)
@@ -223,6 +229,10 @@ logicalrep_worker_find(Oid subid, Oid relid, bool only_running)
 	{
 		LogicalRepWorker *w = &LogicalRepCtx->workers[i];
 
+		/* Skip parallel apply workers. */
+		if (isParallelApplyWorker(w))
+			continue;
+
 		if (w->in_use && w->subid == subid && w->relid == relid &&
 			(!only_running || w->proc))
 		{
@@ -259,11 +269,13 @@ logicalrep_workers_find(Oid subid, bool only_running)
 }
 
 /*
- * Start new apply background worker, if possible.
+ * Start new background worker, if possible.
+ *
+ * Returns true on success, false on failure.
  */
-void
+bool
 logicalrep_worker_launch(Oid dbid, Oid subid, const char *subname, Oid userid,
-						 Oid relid)
+						 Oid relid, dsm_handle subworker_dsm)
 {
 	BackgroundWorker bgw;
 	BackgroundWorkerHandle *bgw_handle;
@@ -272,7 +284,12 @@ logicalrep_worker_launch(Oid dbid, Oid subid, const char *subname, Oid userid,
 	int			slot = 0;
 	LogicalRepWorker *worker = NULL;
 	int			nsyncworkers;
+	int			nparallelapplyworkers;
 	TimestampTz now;
+	bool		is_subworker = (subworker_dsm != DSM_HANDLE_INVALID);
+
+	/* Sanity check: we don't support table sync in subworker. */
+	Assert(!(is_subworker && OidIsValid(relid)));
 
 	ereport(DEBUG1,
 			(errmsg_internal("starting logical replication worker for subscription \"%s\"",
@@ -350,7 +367,19 @@ retry:
 	if (OidIsValid(relid) && nsyncworkers >= max_sync_workers_per_subscription)
 	{
 		LWLockRelease(LogicalRepWorkerLock);
-		return;
+		return false;
+	}
+
+	nparallelapplyworkers = logicalrep_parallel_apply_worker_count(subid);
+
+	/*
+	 * Return silently if the number of parallel apply workers reached the
+	 * limit per subscription.
+	 */
+	if (is_subworker && nparallelapplyworkers >= max_parallel_apply_workers_per_subscription)
+	{
+		LWLockRelease(LogicalRepWorkerLock);
+		return false;
 	}
 
 	/*
@@ -364,7 +393,7 @@ retry:
 				(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
 				 errmsg("out of logical replication worker slots"),
 				 errhint("You might need to increase max_logical_replication_workers.")));
-		return;
+		return false;
 	}
 
 	/* Prepare the worker slot. */
@@ -379,6 +408,7 @@ retry:
 	worker->relstate = SUBREL_STATE_UNKNOWN;
 	worker->relstate_lsn = InvalidXLogRecPtr;
 	worker->stream_fileset = NULL;
+	worker->apply_leader_pid = is_subworker ? MyProcPid : InvalidPid;
 	worker->last_lsn = InvalidXLogRecPtr;
 	TIMESTAMP_NOBEGIN(worker->last_send_time);
 	TIMESTAMP_NOBEGIN(worker->last_recv_time);
@@ -396,10 +426,18 @@ retry:
 		BGWORKER_BACKEND_DATABASE_CONNECTION;
 	bgw.bgw_start_time = BgWorkerStart_RecoveryFinished;
 	snprintf(bgw.bgw_library_name, BGW_MAXLEN, "postgres");
-	snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyWorkerMain");
+
+	if (is_subworker)
+		snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ParallelApplyWorkerMain");
+	else
+		snprintf(bgw.bgw_function_name, BGW_MAXLEN, "ApplyWorkerMain");
+
 	if (OidIsValid(relid))
 		snprintf(bgw.bgw_name, BGW_MAXLEN,
 				 "logical replication worker for subscription %u sync %u", subid, relid);
+	else if (is_subworker)
+		snprintf(bgw.bgw_name, BGW_MAXLEN,
+				 "logical replication parallel apply worker for subscription %u", subid);
 	else
 		snprintf(bgw.bgw_name, BGW_MAXLEN,
 				 "logical replication worker for subscription %u", subid);
@@ -409,6 +447,9 @@ retry:
 	bgw.bgw_notify_pid = MyProcPid;
 	bgw.bgw_main_arg = Int32GetDatum(slot);
 
+	if (is_subworker)
+		memcpy(bgw.bgw_extra, &subworker_dsm, sizeof(dsm_handle));
+
 	if (!RegisterDynamicBackgroundWorker(&bgw, &bgw_handle))
 	{
 		/* Failed to start worker, so clean up the worker slot. */
@@ -421,11 +462,11 @@ retry:
 				(errcode(ERRCODE_CONFIGURATION_LIMIT_EXCEEDED),
 				 errmsg("out of background worker slots"),
 				 errhint("You might need to increase max_worker_processes.")));
-		return;
+		return false;
 	}
 
 	/* Now wait until it attaches. */
-	WaitForReplicationWorkerAttach(worker, generation, bgw_handle);
+	return WaitForReplicationWorkerAttach(worker, generation, bgw_handle);
 }
 
 /*
@@ -436,19 +477,53 @@ void
 logicalrep_worker_stop(Oid subid, Oid relid)
 {
 	LogicalRepWorker *worker;
-	uint16		generation;
 
 	LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
 
 	worker = logicalrep_worker_find(subid, relid, false);
 
-	/* No worker, nothing to do. */
-	if (!worker)
+	if (worker)
 	{
-		LWLockRelease(LogicalRepWorkerLock);
-		return;
+		Assert(!isParallelApplyWorker(worker));
+		logicalrep_worker_stop_internal(worker);
 	}
 
+	LWLockRelease(LogicalRepWorkerLock);
+}
+
+/*
+ * Stop the logical replication worker corresponding to the input slot number,
+ * and wait until it detaches from the slot.
+ */
+void
+logicalrep_worker_stop_by_slot(int slot_no, uint16 generation)
+{
+	LogicalRepWorker *worker;
+
+	LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+
+	worker = &LogicalRepCtx->workers[slot_no];
+
+	/*
+	 * Only stop the worker if the generation matches and the worker is alive.
+	 */
+	if (worker->generation == generation && worker->proc)
+		logicalrep_worker_stop_internal(worker);
+
+	LWLockRelease(LogicalRepWorkerLock);
+}
+
+/*
+ * Workhorse for logicalrep_worker_stop(), logicalrep_worker_detach() and
+ * logicalrep_worker_stop_by_slot(). Stop the worker and wait for it to die.
+ */
+static void
+logicalrep_worker_stop_internal(LogicalRepWorker *worker)
+{
+	uint16		generation;
+
+	Assert(LWLockHeldByMe(LogicalRepWorkerLock));
+
 	/*
 	 * Remember which generation was our worker so we can check if what we see
 	 * is still the same one.
@@ -485,10 +560,7 @@ logicalrep_worker_stop(Oid subid, Oid relid)
 		 * different, meaning that a different worker has taken the slot.
 		 */
 		if (!worker->in_use || worker->generation != generation)
-		{
-			LWLockRelease(LogicalRepWorkerLock);
 			return;
-		}
 
 		/* Worker has assigned proc, so it has started. */
 		if (worker->proc)
@@ -522,8 +594,6 @@ logicalrep_worker_stop(Oid subid, Oid relid)
 
 		LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
 	}
-
-	LWLockRelease(LogicalRepWorkerLock);
 }
 
 /*
@@ -599,6 +669,29 @@ logicalrep_worker_attach(int slot)
 static void
 logicalrep_worker_detach(void)
 {
+	/*
+	 * If this is the leader apply worker then stop all the parallel apply
+	 * workers previously started from here.
+	 */
+	if (!am_parallel_apply_worker() && !am_tablesync_worker())
+	{
+		List	   *workers;
+		ListCell   *lc;
+
+		LWLockAcquire(LogicalRepWorkerLock, LW_SHARED);
+
+		workers = logicalrep_workers_find(MyLogicalRepWorker->subid, true);
+		foreach(lc, workers)
+		{
+			LogicalRepWorker *w = (LogicalRepWorker *) lfirst(lc);
+
+			if (isParallelApplyWorker(w))
+				logicalrep_worker_stop_internal(w);
+		}
+
+		LWLockRelease(LogicalRepWorkerLock);
+	}
+
 	/* Block concurrent access. */
 	LWLockAcquire(LogicalRepWorkerLock, LW_EXCLUSIVE);
 
@@ -621,6 +714,7 @@ logicalrep_worker_cleanup(LogicalRepWorker *worker)
 	worker->userid = InvalidOid;
 	worker->subid = InvalidOid;
 	worker->relid = InvalidOid;
+	worker->apply_leader_pid = InvalidPid;
 }
 
 /*
@@ -679,6 +773,33 @@ logicalrep_sync_worker_count(Oid subid)
 	return res;
 }
 
+/*
+ * Count the number of registered (but not necessarily running) parallel apply
+ * workers for a subscription.
+ */
+int
+logicalrep_parallel_apply_worker_count(Oid subid)
+{
+	int			i;
+	int			res = 0;
+
+	Assert(LWLockHeldByMe(LogicalRepWorkerLock));
+
+	/*
+	 * Scan all attached parallel apply workers, only counting those which
+	 * have the given subscription id.
+	 */
+	for (i = 0; i < max_logical_replication_workers; i++)
+	{
+		LogicalRepWorker *w = &LogicalRepCtx->workers[i];
+
+		if (w->subid == subid && isParallelApplyWorker(w))
+			res++;
+	}
+
+	return res;
+}
+
 /*
  * ApplyLauncherShmemSize
  *		Compute space needed for replication launcher shared memory
@@ -868,7 +989,7 @@ ApplyLauncherMain(Datum main_arg)
 					wait_time = wal_retrieve_retry_interval;
 
 					logicalrep_worker_launch(sub->dbid, sub->oid, sub->name,
-											 sub->owner, InvalidOid);
+											 sub->owner, InvalidOid, DSM_HANDLE_INVALID);
 				}
 			}
 
diff --git a/src/backend/replication/logical/proto.c b/src/backend/replication/logical/proto.c
index ff8513e2d2..364d5d7c28 100644
--- a/src/backend/replication/logical/proto.c
+++ b/src/backend/replication/logical/proto.c
@@ -1163,10 +1163,14 @@ logicalrep_read_stream_commit(StringInfo in, LogicalRepCommitData *commit_data)
 /*
  * Write STREAM ABORT to the output stream. Note that xid and subxid will be
  * same for the top-level transaction abort.
+ *
+ * If write_abort_lsn is true, send the abort_lsn and abort_time fields,
+ * otherwise don't.
  */
 void
 logicalrep_write_stream_abort(StringInfo out, TransactionId xid,
-							  TransactionId subxid)
+							  TransactionId subxid, XLogRecPtr abort_lsn,
+							  TimestampTz abort_time, bool abort_info)
 {
 	pq_sendbyte(out, LOGICAL_REP_MSG_STREAM_ABORT);
 
@@ -1175,19 +1179,40 @@ logicalrep_write_stream_abort(StringInfo out, TransactionId xid,
 	/* transaction ID */
 	pq_sendint32(out, xid);
 	pq_sendint32(out, subxid);
+
+	if (abort_info)
+	{
+		pq_sendint64(out, abort_lsn);
+		pq_sendint64(out, abort_time);
+	}
 }
 
 /*
  * Read STREAM ABORT from the output stream.
+ *
+ * If read_abort_lsn is true, try to read the abort_lsn and abort_time fields,
+ * otherwise don't.
  */
 void
-logicalrep_read_stream_abort(StringInfo in, TransactionId *xid,
-							 TransactionId *subxid)
+logicalrep_read_stream_abort(StringInfo in,
+							 LogicalRepStreamAbortData *abort_data,
+							 bool read_abort_lsn)
 {
-	Assert(xid && subxid);
+	Assert(abort_data);
+
+	abort_data->xid = pq_getmsgint(in, 4);
+	abort_data->subxid = pq_getmsgint(in, 4);
 
-	*xid = pq_getmsgint(in, 4);
-	*subxid = pq_getmsgint(in, 4);
+	if (read_abort_lsn)
+	{
+		abort_data->abort_lsn = pq_getmsgint64(in);
+		abort_data->abort_time = pq_getmsgint64(in);
+	}
+	else
+	{
+		abort_data->abort_lsn = InvalidXLogRecPtr;
+		abort_data->abort_time = 0;
+	}
 }
 
 /*
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 89cf9f9389..5a20c74eec 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -2839,7 +2839,8 @@ ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
  * disk.
  */
 void
-ReorderBufferAbort(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
+ReorderBufferAbort(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn,
+				   TimestampTz abort_time)
 {
 	ReorderBufferTXN *txn;
 
@@ -2850,6 +2851,8 @@ ReorderBufferAbort(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
 	if (txn == NULL)
 		return;
 
+	txn->xact_time.abort_time = abort_time;
+
 	/* For streamed transactions notify the remote node about the abort. */
 	if (rbtxn_is_streamed(txn))
 	{
@@ -2924,7 +2927,8 @@ ReorderBufferAbortOld(ReorderBuffer *rb, TransactionId oldestRunningXid)
  * to this xid might re-create the transaction incompletely.
  */
 void
-ReorderBufferForget(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
+ReorderBufferForget(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn,
+					TimestampTz abort_time)
 {
 	ReorderBufferTXN *txn;
 
@@ -2935,6 +2939,8 @@ ReorderBufferForget(ReorderBuffer *rb, TransactionId xid, XLogRecPtr lsn)
 	if (txn == NULL)
 		return;
 
+	txn->xact_time.abort_time = abort_time;
+
 	/* For streamed transactions notify the remote node about the abort. */
 	if (rbtxn_is_streamed(txn))
 		rb->stream_abort(rb, txn, lsn);
diff --git a/src/backend/replication/logical/tablesync.c b/src/backend/replication/logical/tablesync.c
index 831d42016c..47ae9a80dd 100644
--- a/src/backend/replication/logical/tablesync.c
+++ b/src/backend/replication/logical/tablesync.c
@@ -609,7 +609,8 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 												 MySubscription->oid,
 												 MySubscription->name,
 												 MyLogicalRepWorker->userid,
-												 rstate->relid);
+												 rstate->relid,
+												 DSM_HANDLE_INVALID);
 						hentry->last_start_time = now;
 					}
 				}
@@ -630,6 +631,9 @@ process_syncing_tables_for_apply(XLogRecPtr current_lsn)
 void
 process_syncing_tables(XLogRecPtr current_lsn)
 {
+	if (am_parallel_apply_worker())
+		return;
+
 	if (am_tablesync_worker())
 		process_syncing_tables_for_sync(current_lsn);
 	else
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index eaca406d30..2bff1dbc74 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -22,8 +22,56 @@
  * STREAMED TRANSACTIONS
  * ---------------------
  * Streamed transactions (large transactions exceeding a memory limit on the
- * upstream) are not applied immediately, but instead, the data is written
- * to temporary files and then applied at once when the final commit arrives.
+ * upstream) are applied using one of two approaches:
+ *
+ * 1) Parallel apply workers
+ *
+ * If streaming = parallel, we assign a new parallel apply worker (if
+ * available) as soon as the xact's first stream is received. The leader apply
+ * worker will send changes to this new worker via shared memory. We keep this
+ * worker assigned till the transaction commit is received and also wait for
+ * the worker to finish at commit. This preserves commit ordering and avoids
+ * file I/O in most cases. We still need to spill to a file if there is no
+ * worker available. It is important to maintain commit order to avoid failures
+ * due to (a) transaction dependencies, say if we insert a row in the first
+ * transaction and update it in the second transaction then allowing to apply
+ * both in parallel can lead to failure in the update. (b) deadlocks, allowing
+ * transactions that update the same set of rows/tables in opposite order to be
+ * applied in parallel can lead to deadlocks.
+ *
+ * We maintain a worker pool to avoid restarting workers for each streaming
+ * transaction. We maintain each worker's information in the
+ * ParallelApplyWorkersList. After successfully, launching a new worker it's
+ * information is added to the ParallelApplyWorkersList. Once the worker
+ * finishes applying the transaction, we mark it available for use. Now,
+ * before starting a new worker to apply the streaming transaction, we check
+ * the list and use any worker, if available. Note that we maintain a maximum
+ * of half the max_parallel_apply_workers_per_subscription workers in the pool
+ * and after that, we simply exit the worker after applying the transaction.
+ * This worker pool threshold is a bit arbitrary and we can provide a guc for
+ * this in the future if required.
+ *
+ * The leader apply worker will create separate dynamic shared memory segment
+ * when each parallel apply worker starts. The reason for this design is that
+ * we cannot count how many workers will be started. It may be possible to
+ * allocate enough shared memory in one segment based on the maximum number of
+ * parallel apply workers (max_parallel_apply_workers_per_subscription), but this
+ * may waste some memory if no process is actually started.
+ *
+ * The dynamic shared memory segment will contain  (1) a shm_mq that can be
+ * used to send changes in the transaction from leader apply worker to parallel
+ * apply worker (2) another shm_mq that can be used to send errors (and other
+ * messages reported via elog/ereport) from the parallel apply worker to leader
+ * apply worker (3) necessary information to be shared among parallel apply
+ * workers and leader apply worker(i.e. in_parallel_apply_xact flag and the
+ * corresponding LogicalRepWorker slot information).
+ *
+ * 2) Write to temporary files and apply when the final commit arrives
+ *
+ * If streaming = true, or if streaming = parallel but there are not parallel
+ * apply workers available to handle the streamed transaction, the data is
+ * written to temporary files and then applied at once when the final commit
+ * arrives.
  *
  * Unlike the regular (non-streamed) case, handling streamed transactions has
  * to handle aborts of both the toplevel transaction and subtransactions. This
@@ -219,20 +267,35 @@ typedef struct ApplyExecutionData
 	PartitionTupleRouting *proute;	/* partition routing info */
 } ApplyExecutionData;
 
-/* Struct for saving and restoring apply errcontext information */
-typedef struct ApplyErrorCallbackArg
+/*
+ * What action to take for the transaction.
+ *
+ * TRANS_LEADER_APPLY means that we are in the leader apply worker and changes
+ * of the transaction are applied directly in the worker.
+ *
+ * TRANS_LEADER_SERIALIZE means that we are in leader apply worker and changes
+ * are written to temporary files and then applied when the final commit
+ * arrives.
+ *
+ * TRANS_LEADER_SEND_TO_PARALLEL means that we are in the leader apply worker
+ * and need to send the changes to the parallel apply worker.
+ *
+ * TRANS_PARALLEL_APPLY means that we are in the parallel apply worker and
+ * changes of the transaction are applied directly in the worker.
+ */
+typedef enum
 {
-	LogicalRepMsgType command;	/* 0 if invalid */
-	LogicalRepRelMapEntry *rel;
+	/* The action for non-streaming transactions. */
+	TRANS_LEADER_APPLY,
 
-	/* Remote node information */
-	int			remote_attnum;	/* -1 if invalid */
-	TransactionId remote_xid;
-	XLogRecPtr	finish_lsn;
-	char	   *origin_name;
-} ApplyErrorCallbackArg;
+	/* Actions for streaming transactions. */
+	TRANS_LEADER_SERIALIZE,
+	TRANS_LEADER_SEND_TO_PARALLEL,
+	TRANS_PARALLEL_APPLY
+} TransApplyAction;
 
-static ApplyErrorCallbackArg apply_error_callback_arg =
+/* errcontext tracker */
+ApplyErrorCallbackArg apply_error_callback_arg =
 {
 	.command = 0,
 	.rel = NULL,
@@ -242,7 +305,9 @@ static ApplyErrorCallbackArg apply_error_callback_arg =
 	.origin_name = NULL,
 };
 
-static MemoryContext ApplyMessageContext = NULL;
+ErrorContextCallback	*apply_error_context_stack = NULL;
+
+MemoryContext ApplyMessageContext = NULL;
 MemoryContext ApplyContext = NULL;
 
 /* per stream context for streaming transactions */
@@ -251,7 +316,7 @@ static MemoryContext LogicalStreamingContext = NULL;
 WalReceiverConn *LogRepWorkerWalRcvConn = NULL;
 
 Subscription *MySubscription = NULL;
-static bool MySubscriptionValid = false;
+bool MySubscriptionValid = false;
 
 bool		in_remote_transaction = false;
 static XLogRecPtr remote_final_lsn = InvalidXLogRecPtr;
@@ -259,19 +324,27 @@ static XLogRecPtr remote_final_lsn = InvalidXLogRecPtr;
 /* fields valid only when processing streamed transaction */
 static bool in_streamed_transaction = false;
 
-static TransactionId stream_xid = InvalidTransactionId;
+TransactionId stream_xid = InvalidTransactionId;
+
+/*
+ * The number of changes sent to parallel apply workers during one streaming
+ * block.
+ */
+static uint32 nchanges = 0;
 
 /*
  * We enable skipping all data modification changes (INSERT, UPDATE, etc.) for
  * the subscription if the remote transaction's finish LSN matches the subskiplsn.
  * Once we start skipping changes, we don't stop it until we skip all changes of
  * the transaction even if pg_subscription is updated and MySubscription->skiplsn
- * gets changed or reset during that. Also, in streaming transaction cases, we
- * don't skip receiving and spooling the changes since we decide whether or not
+ * gets changed or reset during that. Also, in streaming transaction cases (streaming = on),
+ * we don't skip receiving and spooling the changes since we decide whether or not
  * to skip applying the changes when starting to apply changes. The subskiplsn is
  * cleared after successfully skipping the transaction or applying non-empty
  * transaction. The latter prevents the mistakenly specified subskiplsn from
- * being left.
+ * being left. Note that we cannot skip the streaming transactions when using
+ * parallel apply workers because we cannot get the finish LSN before
+ * applying the changes.
  */
 static XLogRecPtr skip_xact_finish_lsn = InvalidXLogRecPtr;
 #define is_skipping_changes() (unlikely(!XLogRecPtrIsInvalid(skip_xact_finish_lsn)))
@@ -324,9 +397,6 @@ static void maybe_reread_subscription(void);
 
 static void DisableSubscriptionAndExit(void);
 
-/* prototype needed because of stream_commit */
-static void apply_dispatch(StringInfo s);
-
 static void apply_handle_commit_internal(LogicalRepCommitData *commit_data);
 static void apply_handle_insert_internal(ApplyExecutionData *edata,
 										 ResultRelInfo *relinfo,
@@ -359,10 +429,12 @@ static void stop_skipping_changes(void);
 static void clear_subscription_skip_lsn(XLogRecPtr finish_lsn);
 
 /* Functions for apply error callback */
-static void apply_error_callback(void *arg);
 static inline void set_apply_error_context_xact(TransactionId xid, XLogRecPtr lsn);
 static inline void reset_apply_error_context_info(void);
 
+static TransApplyAction get_transaction_apply_action(TransactionId xid,
+													 ParallelApplyWorkerInfo **winfo);
+
 /*
  * Should this worker apply changes for given relation.
  *
@@ -375,12 +447,34 @@ static inline void reset_apply_error_context_info(void);
  * record + 1 (ie start of next record) and next record can be COMMIT of
  * transaction we are now processing (which is what we set remote_final_lsn
  * to in apply_handle_begin).
+ *
+ * Note that for streaming transactions that are being applied in the parallel
+ * apply worker, we disallow applying changes on a table that is not in
+ * the READY state, because we cannot decide whether to apply the change as we
+ * won't know remote_final_lsn by that time.
+ *
+ * We already checked this in parallel_apply_can_start() before assigning the
+ * streaming transaction to the parallel worker, but it also needs to be
+ * checked here because if the user executes ALTER SUBSCRIPTION ... REFRESH
+ * PUBLICATION in parallel, the new table can be added to pg_subscription_rel
+ * while applying this transaction.
  */
 static bool
 should_apply_changes_for_rel(LogicalRepRelMapEntry *rel)
 {
 	if (am_tablesync_worker())
 		return MyLogicalRepWorker->relid == rel->localreloid;
+	else if (am_parallel_apply_worker())
+	{
+		if (rel->state != SUBREL_STATE_READY)
+			ereport(ERROR,
+					(errmsg("logical replication apply workers for subscription \"%s\" will restart",
+							MySubscription->name),
+					 errdetail("Cannot handle streamed replication transaction using parallel "
+							   "apply workers until all tables are synchronized.")));
+
+		return true;
+	}
 	else
 		return (rel->state == SUBREL_STATE_READY ||
 				(rel->state == SUBREL_STATE_SYNCDONE &&
@@ -426,43 +520,87 @@ end_replication_step(void)
 }
 
 /*
- * Handle streamed transactions.
+ * Handle streamed transactions for both the leader apply worker and the parallel
+ * apply workers.
+ *
+ * In streaming case (receiving a block of streamed transaction), for
+ * SUBSTREAM_ON mode, simply redirect it to a file for the proper toplevel
+ * transaction, and for SUBSTREAM_PARALLEL mode, send the changes to parallel
+ * apply workers (LOGICAL_REP_MSG_RELATION or LOGICAL_REP_MSG_TYPE changes
+ * will be applied by both leader apply worker and parallel apply workers).
  *
- * If in streaming mode (receiving a block of streamed transaction), we
- * simply redirect it to a file for the proper toplevel transaction.
+ * For non-streamed transactions, returns false;
+ * For streamed transactions, returns true if in leader apply worker, false
+ * otherwise.
  *
- * Returns true for streamed transactions, false otherwise (regular mode).
+ * Exception: If the message being processed is LOGICAL_REP_MSG_RELATION
+ * or LOGICAL_REP_MSG_TYPE, return false even if the message needs to be sent
+ * to a parallel apply worker.
  */
 static bool
 handle_streamed_transaction(LogicalRepMsgType action, StringInfo s)
 {
-	TransactionId xid;
+	TransactionId current_xid = InvalidTransactionId;
+	ParallelApplyWorkerInfo *winfo = NULL;
+	TransApplyAction	apply_action;
+
+	apply_action = get_transaction_apply_action(stream_xid, &winfo);
 
 	/* not in streaming mode */
-	if (!in_streamed_transaction)
+	if (apply_action == TRANS_LEADER_APPLY)
 		return false;
 
-	Assert(stream_fd != NULL);
 	Assert(TransactionIdIsValid(stream_xid));
 
 	/*
 	 * We should have received XID of the subxact as the first part of the
 	 * message, so extract it.
 	 */
-	xid = pq_getmsgint(s, 4);
+	current_xid = pq_getmsgint(s, 4);
 
-	if (!TransactionIdIsValid(xid))
+	if (!TransactionIdIsValid(current_xid))
 		ereport(ERROR,
 				(errcode(ERRCODE_PROTOCOL_VIOLATION),
 				 errmsg_internal("invalid transaction ID in streamed replication transaction")));
 
-	/* Add the new subxact to the array (unless already there). */
-	subxact_info_add(xid);
+	switch (apply_action)
+	{
+		case TRANS_LEADER_SERIALIZE:
+			Assert(stream_fd != NULL);
+
+			/* Add the new subxact to the array (unless already there). */
+			subxact_info_add(current_xid);
 
-	/* write the change to the current file */
-	stream_write_change(action, s);
+			/* write the change to the current file */
+			stream_write_change(action, s);
+			return true;
 
-	return true;
+		case TRANS_LEADER_SEND_TO_PARALLEL:
+			Assert(winfo);
+
+			parallel_apply_send_data(winfo, s->len, s->data);
+			nchanges += 1;
+
+			/*
+			 * XXX The publisher side doesn't always send relation/type update
+			 * messages after the streaming transaction, so also update the
+			 * relation/type in leader apply worker here. See function
+			 * cleanup_rel_sync_cache.
+			 */
+			if (action == LOGICAL_REP_MSG_RELATION ||
+				action == LOGICAL_REP_MSG_TYPE)
+				return false;
+			return true;
+
+		case TRANS_PARALLEL_APPLY:
+			/* Define a savepoint for a subxact if needed. */
+			parallel_apply_subxact_info_add(current_xid);
+			return false;
+
+		default:
+			Assert(false);
+			return false;	/* silence compiler warning */
+	}
 }
 
 /*
@@ -898,8 +1036,11 @@ apply_handle_prepare_internal(LogicalRepPreparedTxnData *prepare_data)
 	 * BeginTransactionBlock is necessary to balance the EndTransactionBlock
 	 * called within the PrepareTransactionBlock below.
 	 */
-	BeginTransactionBlock();
-	CommitTransactionCommand(); /* Completes the preceding Begin command. */
+	if (!IsTransactionBlock())
+	{
+		BeginTransactionBlock();
+		CommitTransactionCommand(); /* Completes the preceding Begin command. */
+	}
 
 	/*
 	 * Update origin state so we can restart streaming from correct position
@@ -968,6 +1109,12 @@ apply_handle_prepare(StringInfo s)
 
 /*
  * Handle a COMMIT PREPARED of a previously PREPARED transaction.
+ *
+ * Note that we don't need to wait here if the transaction was prepared in a
+ * parallel apply worker. Because we have already waited for the prepare to
+ * finish in apply_handle_stream_prepare() which will ensure all the operations
+ * in that transaction have happened in the subscriber and no concurrent
+ * transaction can create deadlock or transaction dependency issues.
  */
 static void
 apply_handle_commit_prepared(StringInfo s)
@@ -1011,6 +1158,12 @@ apply_handle_commit_prepared(StringInfo s)
 
 /*
  * Handle a ROLLBACK PREPARED of a previously PREPARED TRANSACTION.
+ *
+ * Note that we don't need to wait here if the transaction was prepared in a
+ * parallel apply worker. Because we have already waited for the prepare to
+ * finish in apply_handle_stream_prepare() which will ensure all the operations
+ * in that transaction have happened in the subscriber and no concurrent
+ * transaction can create deadlock or transaction dependency issues.
  */
 static void
 apply_handle_rollback_prepared(StringInfo s)
@@ -1064,17 +1217,15 @@ apply_handle_rollback_prepared(StringInfo s)
 
 /*
  * Handle STREAM PREPARE.
- *
- * Logic is in two parts:
- * 1. Replay all the spooled operations
- * 2. Mark the transaction as prepared
  */
 static void
 apply_handle_stream_prepare(StringInfo s)
 {
 	LogicalRepPreparedTxnData prepare_data;
+	ParallelApplyWorkerInfo *winfo = NULL;
+	TransApplyAction	apply_action;
 
-	if (in_streamed_transaction)
+	if (in_streamed_transaction || stream_apply_worker)
 		ereport(ERROR,
 				(errcode(ERRCODE_PROTOCOL_VIOLATION),
 				 errmsg_internal("STREAM PREPARE message without STREAM STOP")));
@@ -1088,24 +1239,75 @@ apply_handle_stream_prepare(StringInfo s)
 	logicalrep_read_stream_prepare(s, &prepare_data);
 	set_apply_error_context_xact(prepare_data.xid, prepare_data.prepare_lsn);
 
-	elog(DEBUG1, "received prepare for streamed transaction %u", prepare_data.xid);
+	apply_action = get_transaction_apply_action(prepare_data.xid, &winfo);
 
-	/* Replay all the spooled operations. */
-	apply_spooled_messages(prepare_data.xid, prepare_data.prepare_lsn);
+	switch (apply_action)
+	{
+		case TRANS_LEADER_SERIALIZE:
+			/*
+			 * The transaction has been serialized to file, so replay all the
+			 * spooled operations.
+			 */
+			apply_spooled_messages(prepare_data.xid, prepare_data.prepare_lsn);
 
-	/* Mark the transaction as prepared. */
-	apply_handle_prepare_internal(&prepare_data);
+			/* Mark the transaction as prepared. */
+			apply_handle_prepare_internal(&prepare_data);
 
-	CommitTransactionCommand();
+			CommitTransactionCommand();
 
-	pgstat_report_stat(false);
+			store_flush_position(prepare_data.end_lsn);
 
-	store_flush_position(prepare_data.end_lsn);
+			/* Unlink the files with serialized changes and subxact info. */
+			stream_cleanup_files(MyLogicalRepWorker->subid, prepare_data.xid);
+			break;
 
-	in_remote_transaction = false;
+		case TRANS_LEADER_SEND_TO_PARALLEL:
+			Assert(winfo);
+
+			parallel_apply_replorigin_reset();
+
+			/* Send STREAM PREPARE message to the parallel apply worker. */
+			parallel_apply_send_data(winfo, s->len, s->data);
+
+			/*
+			 * After sending the data to the parallel apply worker, wait for
+			 * that worker to finish. This is necessary to maintain commit
+			 * order which avoids failures due to transaction dependencies and
+			 * deadlocks.
+			 */
+			parallel_apply_wait_for_xact_finish(winfo);
+			parallel_apply_replorigin_setup();
+			parallel_apply_free_worker(winfo, prepare_data.xid);
+
+			store_flush_position(prepare_data.end_lsn);
+			break;
+
+		case TRANS_PARALLEL_APPLY:
+			parallel_apply_replorigin_setup();
 
-	/* unlink the files with serialized changes and subxact info. */
-	stream_cleanup_files(MyLogicalRepWorker->subid, prepare_data.xid);
+			/* Mark the transaction as prepared. */
+			apply_handle_prepare_internal(&prepare_data);
+
+			CommitTransactionCommand();
+
+			parallel_apply_replorigin_reset();
+
+			list_free(subxactlist);
+			subxactlist = NIL;
+
+			parallel_apply_set_in_xact(MyParallelShared, false);
+
+			elog(DEBUG1, "finished processing the transaction finish command");
+			break;
+
+		default:
+			Assert(false);
+			break;
+	}
+
+	pgstat_report_stat(false);
+
+	in_remote_transaction = false;
 
 	/* Process any tables that are being synchronized in parallel. */
 	process_syncing_tables(prepare_data.end_lsn);
@@ -1134,7 +1336,7 @@ apply_handle_origin(StringInfo s)
 	 * ORIGIN message can only come inside streaming transaction or inside
 	 * remote transaction and before any actual writes.
 	 */
-	if (!in_streamed_transaction &&
+	if (!in_streamed_transaction && stream_apply_worker == NULL &&
 		(!in_remote_transaction ||
 		 (IsTransactionState() && !am_tablesync_worker())))
 		ereport(ERROR,
@@ -1149,24 +1351,14 @@ static void
 apply_handle_stream_start(StringInfo s)
 {
 	bool		first_segment;
+	ParallelApplyWorkerInfo *winfo = NULL;
+	TransApplyAction apply_action;
 
-	if (in_streamed_transaction)
+	if (in_streamed_transaction || stream_apply_worker)
 		ereport(ERROR,
 				(errcode(ERRCODE_PROTOCOL_VIOLATION),
 				 errmsg_internal("duplicate STREAM START message")));
 
-	/*
-	 * Start a transaction on stream start, this transaction will be committed
-	 * on the stream stop unless it is a tablesync worker in which case it
-	 * will be committed after processing all the messages. We need the
-	 * transaction for handling the buffile, used for serializing the
-	 * streaming data and subxact info.
-	 */
-	begin_replication_step();
-
-	/* notify handle methods we're processing a remote transaction */
-	in_streamed_transaction = true;
-
 	/* extract XID of the top-level transaction */
 	stream_xid = logicalrep_read_stream_start(s, &first_segment);
 
@@ -1178,35 +1370,91 @@ apply_handle_stream_start(StringInfo s)
 	set_apply_error_context_xact(stream_xid, InvalidXLogRecPtr);
 
 	/*
-	 * Initialize the worker's stream_fileset if we haven't yet. This will be
-	 * used for the entire duration of the worker so create it in a permanent
-	 * context. We create this on the very first streaming message from any
-	 * transaction and then use it for this and other streaming transactions.
-	 * Now, we could create a fileset at the start of the worker as well but
-	 * then we won't be sure that it will ever be used.
+	 * For the first stream start, check if there is any free parallel apply
+	 * worker we can use to process this transaction.
 	 */
-	if (MyLogicalRepWorker->stream_fileset == NULL)
+	if (first_segment)
+		parallel_apply_start_worker(stream_xid);
+
+	apply_action = get_transaction_apply_action(stream_xid, &winfo);
+
+	switch (apply_action)
 	{
-		MemoryContext oldctx;
+		case TRANS_LEADER_SERIALIZE:
+			/*
+			 * Notify handle methods we're processing a remote in-progress
+			 * transaction.
+			 */
+			in_streamed_transaction = true;
 
-		oldctx = MemoryContextSwitchTo(ApplyContext);
+			/*
+			 * Since no parallel apply worker is used for the first stream start,
+			 * serialize all the changes of the transaction.
+			 *
+			 * Start a transaction on stream start, this transaction will be
+			 * committed on the stream stop unless it is a tablesync worker in
+			 * which case it will be committed after processing all the
+			 * messages. We need the transaction for handling the buffile,
+			 * used for serializing the streaming data and subxact info.
+			 */
+			begin_replication_step();
 
-		MyLogicalRepWorker->stream_fileset = palloc(sizeof(FileSet));
-		FileSetInit(MyLogicalRepWorker->stream_fileset);
+			/*
+			 * Initialize the worker's stream_fileset if we haven't yet. This will
+			 * be used for the entire duration of the worker so create it in a
+			 * permanent context. We create this on the very first streaming
+			 * message from any transaction and then use it for this and other
+			 * streaming transactions. Now, we could create a fileset at the start
+			 * of the worker as well but then we won't be sure that it will ever
+			 * be used.
+			 */
+			if (MyLogicalRepWorker->stream_fileset == NULL)
+			{
+				MemoryContext oldctx;
 
-		MemoryContextSwitchTo(oldctx);
-	}
+				oldctx = MemoryContextSwitchTo(ApplyContext);
+
+				MyLogicalRepWorker->stream_fileset = palloc(sizeof(FileSet));
+				FileSetInit(MyLogicalRepWorker->stream_fileset);
 
-	/* open the spool file for this transaction */
-	stream_open_file(MyLogicalRepWorker->subid, stream_xid, first_segment);
+				MemoryContextSwitchTo(oldctx);
+			}
 
-	/* if this is not the first segment, open existing subxact file */
-	if (!first_segment)
-		subxact_info_read(MyLogicalRepWorker->subid, stream_xid);
+			/* Open the spool file for this transaction. */
+			stream_open_file(MyLogicalRepWorker->subid, stream_xid, first_segment);
 
-	pgstat_report_activity(STATE_RUNNING, NULL);
+			/* If this is not the first segment, open existing subxact file. */
+			if (!first_segment)
+				subxact_info_read(MyLogicalRepWorker->subid, stream_xid);
 
-	end_replication_step();
+			end_replication_step();
+			break;
+
+		case TRANS_LEADER_SEND_TO_PARALLEL:
+			Assert(winfo);
+
+			parallel_apply_send_data(winfo, s->len, s->data);
+
+			nchanges = 0;
+
+			/* Cache the parallel apply worker for this transaction. */
+			stream_apply_worker = winfo;
+			break;
+
+		case TRANS_PARALLEL_APPLY:
+			/*
+			 * Make sure the handle apply_dispatch methods are aware we're in a
+			 * remote transaction.
+			 */
+			in_remote_transaction = true;
+			break;
+
+		default:
+			Assert(false);
+			break;
+	}
+
+	pgstat_report_activity(STATE_RUNNING, NULL);
 }
 
 /*
@@ -1215,58 +1463,81 @@ apply_handle_stream_start(StringInfo s)
 static void
 apply_handle_stream_stop(StringInfo s)
 {
-	if (!in_streamed_transaction)
-		ereport(ERROR,
-				(errcode(ERRCODE_PROTOCOL_VIOLATION),
-				 errmsg_internal("STREAM STOP message without STREAM START")));
+	ParallelApplyWorkerInfo *winfo = NULL;
+	TransApplyAction apply_action;
 
-	/*
-	 * Close the file with serialized changes, and serialize information about
-	 * subxacts for the toplevel transaction.
-	 */
-	subxact_info_write(MyLogicalRepWorker->subid, stream_xid);
-	stream_close_file();
+	apply_action = get_transaction_apply_action(stream_xid, &winfo);
 
-	/* We must be in a valid transaction state */
-	Assert(IsTransactionState());
+	switch (apply_action)
+	{
+		case TRANS_LEADER_SERIALIZE:
+			if (!in_streamed_transaction)
+				ereport(ERROR,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+						 errmsg_internal("STREAM STOP message without STREAM START")));
 
-	/* Commit the per-stream transaction */
-	CommitTransactionCommand();
+			/*
+			 * Close the file with serialized changes, and serialize information
+			 * about subxacts for the toplevel transaction.
+			 */
+			subxact_info_write(MyLogicalRepWorker->subid, stream_xid);
+			stream_close_file();
 
-	in_streamed_transaction = false;
+			/* We must be in a valid transaction state */
+			Assert(IsTransactionState());
 
-	/* Reset per-stream context */
-	MemoryContextReset(LogicalStreamingContext);
+			/* Commit the per-stream transaction */
+			CommitTransactionCommand();
+
+			/* Reset per-stream context */
+			MemoryContextReset(LogicalStreamingContext);
+
+			pgstat_report_activity(STATE_IDLE, NULL);
+
+			in_streamed_transaction = false;
+			break;
+
+		case TRANS_LEADER_SEND_TO_PARALLEL:
+			Assert(winfo);
+
+			if (!stream_apply_worker)
+				ereport(ERROR,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+						 errmsg_internal("STREAM STOP message without STREAM START")));
+
+			parallel_apply_send_data(winfo, s->len, s->data);
+
+			elog(DEBUG1, "applied %u changes in the streaming chunk", nchanges);
+
+			stream_apply_worker = NULL;
+
+			pgstat_report_activity(STATE_IDLE, NULL);
+			break;
+
+		case TRANS_PARALLEL_APPLY:
+			pgstat_report_activity(STATE_IDLEINTRANSACTION, NULL);
+			break;
+
+		default:
+			Assert(false);
+			break;
+	}
 
-	pgstat_report_activity(STATE_IDLE, NULL);
 	reset_apply_error_context_info();
 }
 
 /*
- * Handle STREAM abort message.
+ * Handle STREAM ABORT message when the transaction was spilled to disk.
  */
 static void
-apply_handle_stream_abort(StringInfo s)
+serialize_stream_abort(TransactionId xid, TransactionId subxid)
 {
-	TransactionId xid;
-	TransactionId subxid;
-
-	if (in_streamed_transaction)
-		ereport(ERROR,
-				(errcode(ERRCODE_PROTOCOL_VIOLATION),
-				 errmsg_internal("STREAM ABORT message without STREAM STOP")));
-
-	logicalrep_read_stream_abort(s, &xid, &subxid);
-
 	/*
 	 * If the two XIDs are the same, it's in fact abort of toplevel xact, so
 	 * just delete the files with serialized info.
 	 */
 	if (xid == subxid)
-	{
-		set_apply_error_context_xact(xid, InvalidXLogRecPtr);
 		stream_cleanup_files(MyLogicalRepWorker->subid, xid);
-	}
 	else
 	{
 		/*
@@ -1290,8 +1561,6 @@ apply_handle_stream_abort(StringInfo s)
 		bool		found = false;
 		char		path[MAXPGPATH];
 
-		set_apply_error_context_xact(subxid, InvalidXLogRecPtr);
-
 		subidx = -1;
 		begin_replication_step();
 		subxact_info_read(MyLogicalRepWorker->subid, xid);
@@ -1316,7 +1585,6 @@ apply_handle_stream_abort(StringInfo s)
 			cleanup_subxact_info();
 			end_replication_step();
 			CommitTransactionCommand();
-			reset_apply_error_context_info();
 			return;
 		}
 
@@ -1339,6 +1607,97 @@ apply_handle_stream_abort(StringInfo s)
 		end_replication_step();
 		CommitTransactionCommand();
 	}
+}
+
+/*
+ * Handle STREAM ABORT message.
+ */
+static void
+apply_handle_stream_abort(StringInfo s)
+{
+	TransactionId xid;
+	TransactionId subxid;
+	LogicalRepStreamAbortData abort_data;
+	bool read_abort_lsn = false;
+	ParallelApplyWorkerInfo *winfo = NULL;
+	TransApplyAction apply_action;
+
+	if (in_streamed_transaction || stream_apply_worker)
+		ereport(ERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg_internal("STREAM ABORT message without STREAM STOP")));
+
+	/*
+	 * Check whether the publisher sends abort_lsn and abort_time.
+	 *
+	 * Note that the parallel apply worker is only started when the publisher
+	 * sends abort_lsn and abort_time.
+	 */
+	if (am_parallel_apply_worker() ||
+		(MySubscription->stream == SUBSTREAM_PARALLEL &&
+		walrcv_server_version(LogRepWorkerWalRcvConn) >= 160000))
+		read_abort_lsn = true;
+
+	logicalrep_read_stream_abort(s, &abort_data, read_abort_lsn);
+
+	xid = abort_data.xid;
+	subxid = abort_data.subxid;
+
+	set_apply_error_context_xact(subxid, abort_data.abort_lsn);
+
+	apply_action = get_transaction_apply_action(xid, &winfo);
+
+	switch (apply_action)
+	{
+		case TRANS_LEADER_SERIALIZE:
+			/*
+			 * We are in leader apply worker and the transaction has been
+			 * serialized to file.
+			 */
+			serialize_stream_abort(xid, subxid);
+			break;
+
+		case TRANS_LEADER_SEND_TO_PARALLEL:
+			Assert(winfo);
+
+			if (subxid == xid)
+				parallel_apply_replorigin_reset();
+
+			/* Send STREAM ABORT message to the parallel apply worker. */
+			parallel_apply_send_data(winfo, s->len, s->data);
+
+			/*
+			 * After sending the data to the parallel apply worker, wait for that
+			 * worker to finish. This is necessary to maintain commit order which
+			 * avoids failures due to transaction dependencies and deadlocks.
+			 */
+			parallel_apply_wait_for_xact_finish(winfo);
+
+			if (subxid == xid)
+			{
+				parallel_apply_replorigin_setup();
+				parallel_apply_free_worker(winfo, xid);
+			}
+			else
+			{
+				/*
+				 * Set in_parallel_apply_xact to true again as we only aborted the
+				 * subtransaction and the top transaction is still in progress.
+				 */
+				parallel_apply_set_in_xact(winfo->shared, true);
+			}
+			break;
+
+		case TRANS_PARALLEL_APPLY:
+			parallel_apply_stream_abort(&abort_data);
+
+			elog(DEBUG1, "finished processing the transaction finish command");
+			break;
+
+		default:
+			Assert(false);
+			break;
+	}
 
 	reset_apply_error_context_info();
 }
@@ -1470,8 +1829,10 @@ apply_handle_stream_commit(StringInfo s)
 {
 	TransactionId xid;
 	LogicalRepCommitData commit_data;
+	ParallelApplyWorkerInfo *winfo = NULL;
+	TransApplyAction apply_action;
 
-	if (in_streamed_transaction)
+	if (in_streamed_transaction || stream_apply_worker)
 		ereport(ERROR,
 				(errcode(ERRCODE_PROTOCOL_VIOLATION),
 				 errmsg_internal("STREAM COMMIT message without STREAM STOP")));
@@ -1479,14 +1840,72 @@ apply_handle_stream_commit(StringInfo s)
 	xid = logicalrep_read_stream_commit(s, &commit_data);
 	set_apply_error_context_xact(xid, commit_data.commit_lsn);
 
-	elog(DEBUG1, "received commit for streamed transaction %u", xid);
+	apply_action = get_transaction_apply_action(xid, &winfo);
+
+	switch (apply_action)
+	{
+		case TRANS_LEADER_SERIALIZE:
+			/*
+			 * The transaction has been serialized to file, so replay all the
+			 * spooled operations.
+			 */
+			apply_spooled_messages(xid, commit_data.commit_lsn);
+
+			apply_handle_commit_internal(&commit_data);
 
-	apply_spooled_messages(xid, commit_data.commit_lsn);
+			/* Unlink the files with serialized changes and subxact info. */
+			stream_cleanup_files(MyLogicalRepWorker->subid, xid);
+			break;
 
-	apply_handle_commit_internal(&commit_data);
+		case TRANS_LEADER_SEND_TO_PARALLEL:
+			Assert(winfo);
 
-	/* unlink the files with serialized changes and subxact info */
-	stream_cleanup_files(MyLogicalRepWorker->subid, xid);
+			parallel_apply_replorigin_reset();
+
+			/* Send STREAM COMMIT message to the parallel apply worker. */
+			parallel_apply_send_data(winfo, s->len, s->data);
+
+			/*
+			 * After sending the data to the parallel apply worker, wait for
+			 * that worker to finish. This is necessary to maintain commit
+			 * order which avoids failures due to transaction dependencies and
+			 * deadlocks.
+			 */
+			parallel_apply_wait_for_xact_finish(winfo);
+			parallel_apply_replorigin_setup();
+
+			pgstat_report_stat(false);
+			store_flush_position(commit_data.end_lsn);
+			stop_skipping_changes();
+
+			parallel_apply_free_worker(winfo, xid);
+
+			/*
+			 * The transaction is either non-empty or skipped, so we clear the
+			 * subskiplsn.
+			 */
+			clear_subscription_skip_lsn(commit_data.commit_lsn);
+			break;
+
+		case TRANS_PARALLEL_APPLY:
+			parallel_apply_replorigin_setup();
+
+			apply_handle_commit_internal(&commit_data);
+
+			parallel_apply_replorigin_reset();
+
+			list_free(subxactlist);
+			subxactlist = NIL;
+
+			parallel_apply_set_in_xact(MyParallelShared, false);
+
+			elog(DEBUG1, "finished processing the transaction finish command");
+			break;
+
+		default:
+			Assert(false);
+			break;
+	}
 
 	/* Process any tables that are being synchronized in parallel. */
 	process_syncing_tables(commit_data.end_lsn);
@@ -1530,6 +1949,13 @@ apply_handle_commit_internal(LogicalRepCommitData *commit_data)
 		replorigin_session_origin_timestamp = commit_data->committime;
 
 		CommitTransactionCommand();
+
+		if (IsTransactionBlock())
+		{
+			EndTransactionBlock(false);
+			CommitTransactionCommand();
+		}
+
 		pgstat_report_stat(false);
 
 		store_flush_position(commit_data->end_lsn);
@@ -2467,7 +2893,7 @@ apply_handle_truncate(StringInfo s)
 /*
  * Logical replication protocol message dispatcher.
  */
-static void
+void
 apply_dispatch(StringInfo s)
 {
 	LogicalRepMsgType action = pq_getmsgbyte(s);
@@ -2636,6 +3062,10 @@ store_flush_position(XLogRecPtr remote_lsn)
 {
 	FlushPosition *flushpos;
 
+	/* Skip if not the leader apply worker */
+	if (am_parallel_apply_worker())
+		return;
+
 	/* Need to do this in permanent context */
 	MemoryContextSwitchTo(ApplyContext);
 
@@ -2650,7 +3080,7 @@ store_flush_position(XLogRecPtr remote_lsn)
 
 
 /* Update statistics of the worker. */
-static void
+void
 UpdateWorkerStats(XLogRecPtr last_lsn, TimestampTz send_time, bool reply)
 {
 	MyLogicalRepWorker->last_lsn = last_lsn;
@@ -2700,6 +3130,7 @@ LogicalRepApplyLoop(XLogRecPtr last_received)
 	errcallback.callback = apply_error_callback;
 	errcallback.previous = error_context_stack;
 	error_context_stack = &errcallback;
+	apply_error_context_stack = error_context_stack;
 
 	/* This outer loop iterates once per wait. */
 	for (;;)
@@ -2802,7 +3233,8 @@ LogicalRepApplyLoop(XLogRecPtr last_received)
 		/* confirm all writes so far */
 		send_feedback(last_received, false, false);
 
-		if (!in_remote_transaction && !in_streamed_transaction)
+		if (!in_remote_transaction && !in_streamed_transaction
+			&& !stream_apply_worker)
 		{
 			/*
 			 * If we didn't get any transactions for a while there might be
@@ -2914,6 +3346,7 @@ LogicalRepApplyLoop(XLogRecPtr last_received)
 
 	/* Pop the error context stack */
 	error_context_stack = errcallback.previous;
+	apply_error_context_stack = error_context_stack;
 
 	/* All done */
 	walrcv_endstreaming(LogRepWorkerWalRcvConn, &tli);
@@ -3114,7 +3547,7 @@ maybe_reread_subscription(void)
 /*
  * Callback from subscription syscache invalidation.
  */
-static void
+void
 subscription_change_cb(Datum arg, int cacheid, uint32 hashvalue)
 {
 	MySubscriptionValid = false;
@@ -3569,37 +4002,14 @@ start_apply(XLogRecPtr origin_startpos)
 	PG_END_TRY();
 }
 
-/* Logical Replication Apply worker entry point */
+/*
+ * Initialize the database connection, in-memory subscription and necessary
+ * config options.
+ */
 void
-ApplyWorkerMain(Datum main_arg)
+InitializeApplyWorker(void)
 {
-	int			worker_slot = DatumGetInt32(main_arg);
 	MemoryContext oldctx;
-	char		originname[NAMEDATALEN];
-	XLogRecPtr	origin_startpos = InvalidXLogRecPtr;
-	char	   *myslotname = NULL;
-	WalRcvStreamOptions options;
-	int			server_version;
-
-	/* Attach to slot */
-	logicalrep_worker_attach(worker_slot);
-
-	/* Setup signal handling */
-	pqsignal(SIGHUP, SignalHandlerForConfigReload);
-	pqsignal(SIGTERM, die);
-	BackgroundWorkerUnblockSignals();
-
-	/*
-	 * We don't currently need any ResourceOwner in a walreceiver process, but
-	 * if we did, we could call CreateAuxProcessResourceOwner here.
-	 */
-
-	/* Initialise stats to a sanish value */
-	MyLogicalRepWorker->last_send_time = MyLogicalRepWorker->last_recv_time =
-		MyLogicalRepWorker->reply_time = GetCurrentTimestamp();
-
-	/* Load the libpq-specific functions */
-	load_file("libpqwalreceiver", false);
 
 	/* Run as replica session replication role. */
 	SetConfigOption("session_replication_role", "replica",
@@ -3659,12 +4069,50 @@ ApplyWorkerMain(Datum main_arg)
 		ereport(LOG,
 				(errmsg("logical replication table synchronization worker for subscription \"%s\", table \"%s\" has started",
 						MySubscription->name, get_rel_name(MyLogicalRepWorker->relid))));
+	else if (am_parallel_apply_worker())
+		ereport(LOG,
+				(errmsg("logical replication parallel apply worker for subscription \"%s\" has started",
+						MySubscription->name)));
 	else
 		ereport(LOG,
 				(errmsg("logical replication apply worker for subscription \"%s\" has started",
 						MySubscription->name)));
 
 	CommitTransactionCommand();
+}
+
+/* Logical Replication Apply worker entry point */
+void
+ApplyWorkerMain(Datum main_arg)
+{
+	int			worker_slot = DatumGetInt32(main_arg);
+	char		originname[NAMEDATALEN];
+	XLogRecPtr	origin_startpos = InvalidXLogRecPtr;
+	char	   *myslotname = NULL;
+	WalRcvStreamOptions options;
+	int			server_version;
+
+	/* Attach to slot */
+	logicalrep_worker_attach(worker_slot);
+
+	/* Setup signal handling */
+	pqsignal(SIGHUP, SignalHandlerForConfigReload);
+	pqsignal(SIGTERM, die);
+	BackgroundWorkerUnblockSignals();
+
+	/*
+	 * We don't currently need any ResourceOwner in a walreceiver process, but
+	 * if we did, we could call CreateAuxProcessResourceOwner here.
+	 */
+
+	/* Initialise stats to a sanish value */
+	MyLogicalRepWorker->last_send_time = MyLogicalRepWorker->last_recv_time =
+		MyLogicalRepWorker->reply_time = GetCurrentTimestamp();
+
+	/* Load the libpq-specific functions */
+	load_file("libpqwalreceiver", false);
+
+	InitializeApplyWorker();
 
 	/* Connect to the origin and start the replication. */
 	elog(DEBUG1, "connecting to publisher using connection string \"%s\"",
@@ -3687,7 +4135,7 @@ ApplyWorkerMain(Datum main_arg)
 	}
 	else
 	{
-		/* This is main apply worker */
+		/* This is the leader apply worker */
 		RepOriginId originid;
 		TimeLineID	startpointTLI;
 		char	   *err;
@@ -3751,6 +4199,7 @@ ApplyWorkerMain(Datum main_arg)
 
 	server_version = walrcv_server_version(LogRepWorkerWalRcvConn);
 	options.proto.logical.proto_version =
+		server_version >= 160000 ? LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM :
 		server_version >= 150000 ? LOGICALREP_PROTO_TWOPHASE_VERSION_NUM :
 		server_version >= 140000 ? LOGICALREP_PROTO_STREAM_VERSION_NUM :
 		LOGICALREP_PROTO_VERSION_NUM;
@@ -3854,6 +4303,15 @@ IsLogicalWorker(void)
 	return MyLogicalRepWorker != NULL;
 }
 
+/*
+ * Is current process a logical replication parallel apply worker?
+ */
+bool
+IsLogicalParallelApplyWorker(void)
+{
+	return am_parallel_apply_worker();
+}
+
 /*
  * Start skipping changes of the transaction if the given LSN matches the
  * LSN specified by subscription's skiplsn.
@@ -3916,7 +4374,8 @@ clear_subscription_skip_lsn(XLogRecPtr finish_lsn)
 	XLogRecPtr	myskiplsn = MySubscription->skiplsn;
 	bool		started_tx = false;
 
-	if (likely(XLogRecPtrIsInvalid(myskiplsn)))
+	if (likely(XLogRecPtrIsInvalid(myskiplsn)) ||
+		am_parallel_apply_worker())
 		return;
 
 	if (!IsTransactionState())
@@ -3988,7 +4447,7 @@ clear_subscription_skip_lsn(XLogRecPtr finish_lsn)
 }
 
 /* Error callback to give more context info about the change being applied */
-static void
+void
 apply_error_callback(void *arg)
 {
 	ApplyErrorCallbackArg *errarg = &apply_error_callback_arg;
@@ -4016,23 +4475,47 @@ apply_error_callback(void *arg)
 					   errarg->remote_xid,
 					   LSN_FORMAT_ARGS(errarg->finish_lsn));
 	}
-	else if (errarg->remote_attnum < 0)
-		errcontext("processing remote data for replication origin \"%s\" during \"%s\" for replication target relation \"%s.%s\" in transaction %u finished at %X/%X",
-				   errarg->origin_name,
-				   logicalrep_message_type(errarg->command),
-				   errarg->rel->remoterel.nspname,
-				   errarg->rel->remoterel.relname,
-				   errarg->remote_xid,
-				   LSN_FORMAT_ARGS(errarg->finish_lsn));
 	else
-		errcontext("processing remote data for replication origin \"%s\" during \"%s\" for replication target relation \"%s.%s\" column \"%s\" in transaction %u finished at %X/%X",
-				   errarg->origin_name,
-				   logicalrep_message_type(errarg->command),
-				   errarg->rel->remoterel.nspname,
-				   errarg->rel->remoterel.relname,
-				   errarg->rel->remoterel.attnames[errarg->remote_attnum],
-				   errarg->remote_xid,
-				   LSN_FORMAT_ARGS(errarg->finish_lsn));
+	{
+		if (errarg->remote_attnum < 0)
+		{
+			if (XLogRecPtrIsInvalid(errarg->finish_lsn))
+				errcontext("processing remote data for replication origin \"%s\" during \"%s\" for replication target relation \"%s.%s\" in transaction %u",
+						   errarg->origin_name,
+						   logicalrep_message_type(errarg->command),
+						   errarg->rel->remoterel.nspname,
+						   errarg->rel->remoterel.relname,
+						   errarg->remote_xid);
+			else
+				errcontext("processing remote data for replication origin \"%s\" during \"%s\" for replication target relation \"%s.%s\" in transaction %u finished at %X/%X",
+						   errarg->origin_name,
+						   logicalrep_message_type(errarg->command),
+						   errarg->rel->remoterel.nspname,
+						   errarg->rel->remoterel.relname,
+						   errarg->remote_xid,
+						   LSN_FORMAT_ARGS(errarg->finish_lsn));
+		}
+		else
+		{
+			if (XLogRecPtrIsInvalid(errarg->finish_lsn))
+				errcontext("processing remote data for replication origin \"%s\" during \"%s\" for replication target relation \"%s.%s\" column \"%s\" in transaction %u",
+						   errarg->origin_name,
+						   logicalrep_message_type(errarg->command),
+						   errarg->rel->remoterel.nspname,
+						   errarg->rel->remoterel.relname,
+						   errarg->rel->remoterel.attnames[errarg->remote_attnum],
+						   errarg->remote_xid);
+			else
+				errcontext("processing remote data for replication origin \"%s\" during \"%s\" for replication target relation \"%s.%s\" column \"%s\" in transaction %u finished at %X/%X",
+						   errarg->origin_name,
+						   logicalrep_message_type(errarg->command),
+						   errarg->rel->remoterel.nspname,
+						   errarg->rel->remoterel.relname,
+						   errarg->rel->remoterel.attnames[errarg->remote_attnum],
+						   errarg->remote_xid,
+						   LSN_FORMAT_ARGS(errarg->finish_lsn));
+		}
+	}
 }
 
 /* Set transaction information of apply error callback */
@@ -4052,3 +4535,28 @@ reset_apply_error_context_info(void)
 	apply_error_callback_arg.remote_attnum = -1;
 	set_apply_error_context_xact(InvalidTransactionId, InvalidXLogRecPtr);
 }
+
+/*
+ * Return the action to take for the given transaction. *winfo is assigned to
+ * the destination parallel worker info (if the action is
+ * TRANS_LEADER_SEND_TO_PARALLEL), otherwise *winfo is assigned NULL.
+ */
+static TransApplyAction
+get_transaction_apply_action(TransactionId xid, ParallelApplyWorkerInfo **winfo)
+{
+	*winfo = NULL;
+
+	if (am_parallel_apply_worker())
+		return TRANS_PARALLEL_APPLY;
+	else if (in_remote_transaction)
+		return TRANS_LEADER_APPLY;
+
+	/*
+	 * Check if we are processing this transaction using a parallel apply
+	 * worker and if so, send the changes to that worker.
+	 */
+	else if ((*winfo = parallel_apply_find_worker(xid)))
+		return TRANS_LEADER_SEND_TO_PARALLEL;
+	else
+		return TRANS_LEADER_SERIALIZE;
+}
diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index 62e0ffecd8..98dddd821c 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -369,7 +369,7 @@ parse_output_parameters(List *options, PGOutputData *data)
 						 errmsg("conflicting or redundant options")));
 			streaming_given = true;
 
-			data->streaming = defGetBoolean(defel);
+			data->streaming = defGetStreamingMode(defel);
 		}
 		else if (strcmp(defel->defname, "two_phase") == 0)
 		{
@@ -461,13 +461,20 @@ pgoutput_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 		 * we only allow it with sufficient version of the protocol, and when
 		 * the output plugin supports it.
 		 */
-		if (!data->streaming)
+		if (data->streaming == SUBSTREAM_OFF)
 			ctx->streaming = false;
-		else if (data->protocol_version < LOGICALREP_PROTO_STREAM_VERSION_NUM)
+		else if (data->streaming == SUBSTREAM_ON &&
+				 data->protocol_version < LOGICALREP_PROTO_STREAM_VERSION_NUM)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("requested proto_version=%d does not support streaming, need %d or higher",
 							data->protocol_version, LOGICALREP_PROTO_STREAM_VERSION_NUM)));
+		else if (data->streaming == SUBSTREAM_PARALLEL &&
+				 data->protocol_version < LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM)
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					 errmsg("requested proto_version=%d does not support streaming=parallel mode, need %d or higher",
+							data->protocol_version, LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM)));
 		else if (!ctx->streaming)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
@@ -513,7 +520,7 @@ pgoutput_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 		 * Disable the streaming and prepared transactions during the slot
 		 * initialization mode.
 		 */
-		ctx->streaming = false;
+		ctx->streaming = SUBSTREAM_OFF;
 		ctx->twophase = false;
 	}
 }
@@ -1843,6 +1850,8 @@ pgoutput_stream_abort(struct LogicalDecodingContext *ctx,
 					  XLogRecPtr abort_lsn)
 {
 	ReorderBufferTXN *toptxn;
+	PGOutputData *data = (PGOutputData *) ctx->output_plugin_private;
+	bool abort_info = (data->streaming == SUBSTREAM_PARALLEL);
 
 	/*
 	 * The abort should happen outside streaming block, even for streamed
@@ -1856,7 +1865,8 @@ pgoutput_stream_abort(struct LogicalDecodingContext *ctx,
 	Assert(rbtxn_is_streamed(toptxn));
 
 	OutputPluginPrepareWrite(ctx, true);
-	logicalrep_write_stream_abort(ctx->out, toptxn->xid, txn->xid);
+	logicalrep_write_stream_abort(ctx->out, toptxn->xid, txn->xid, abort_lsn, txn->xact_time.abort_time, abort_info);
+
 	OutputPluginWrite(ctx, true);
 
 	cleanup_rel_sync_cache(toptxn->xid, false);
diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c
index 21a9fc0fdd..9cd54287b6 100644
--- a/src/backend/storage/ipc/procsignal.c
+++ b/src/backend/storage/ipc/procsignal.c
@@ -22,6 +22,7 @@
 #include "commands/async.h"
 #include "miscadmin.h"
 #include "pgstat.h"
+#include "replication/logicalworker.h"
 #include "replication/walsender.h"
 #include "storage/condition_variable.h"
 #include "storage/ipc.h"
@@ -657,6 +658,9 @@ procsignal_sigusr1_handler(SIGNAL_ARGS)
 	if (CheckProcSignal(PROCSIG_LOG_MEMORY_CONTEXT))
 		HandleLogMemoryContextInterrupt();
 
+	if (CheckProcSignal(PROCSIG_PARALLEL_APPLY_MESSAGE))
+		HandleParallelApplyMessageInterrupt();
+
 	if (CheckProcSignal(PROCSIG_RECOVERY_CONFLICT_DATABASE))
 		RecoveryConflictInterrupt(PROCSIG_RECOVERY_CONFLICT_DATABASE);
 
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 35eff28bd3..0ee50020d7 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -3377,6 +3377,9 @@ ProcessInterrupts(void)
 
 	if (LogMemoryContextPending)
 		ProcessLogMemoryContextInterrupt();
+
+	if (ParallelApplyMessagePending)
+		HandleParallelApplyMessages();
 }
 
 /*
diff --git a/src/backend/utils/activity/wait_event.c b/src/backend/utils/activity/wait_event.c
index 92f24a6c9b..c96647c4ed 100644
--- a/src/backend/utils/activity/wait_event.c
+++ b/src/backend/utils/activity/wait_event.c
@@ -388,6 +388,9 @@ pgstat_get_wait_ipc(WaitEventIPC w)
 		case WAIT_EVENT_HASH_GROW_BUCKETS_REINSERT:
 			event_name = "HashGrowBucketsReinsert";
 			break;
+		case WAIT_EVENT_LOGICAL_PARALLEL_APPLY_STATE_CHANGE:
+			event_name = "LogicalParallelApplyStateChange";
+			break;
 		case WAIT_EVENT_LOGICAL_SYNC_DATA:
 			event_name = "LogicalSyncData";
 			break;
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 550e95056c..84f6a11357 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -2973,6 +2973,18 @@ struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"max_parallel_apply_workers_per_subscription",
+			PGC_SIGHUP,
+			REPLICATION_SUBSCRIBERS,
+			gettext_noop("Maximum number of parallel apply workers per subscription."),
+			NULL,
+		},
+		&max_parallel_apply_workers_per_subscription,
+		2, 0, MAX_BACKENDS,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"log_rotation_age", PGC_SIGHUP, LOGGING_WHERE,
 			gettext_noop("Sets the amount of time to wait before forcing "
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 2ae76e5cfb..6603f0e977 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -360,6 +360,7 @@
 #max_logical_replication_workers = 4	# taken from max_worker_processes
 					# (change requires restart)
 #max_sync_workers_per_subscription = 2	# taken from max_logical_replication_workers
+#max_parallel_apply_workers_per_subscription = 2	# taken from max_logical_replication_workers
 
 
 #------------------------------------------------------------------------------
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 67b6d9079e..026cf46828 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4480,7 +4480,7 @@ getSubscriptions(Archive *fout)
 	if (fout->remoteVersion >= 140000)
 		appendPQExpBufferStr(query, " s.substream,\n");
 	else
-		appendPQExpBufferStr(query, " false AS substream,\n");
+		appendPQExpBufferStr(query, " 'f' AS substream,\n");
 
 	if (fout->remoteVersion >= 150000)
 		appendPQExpBufferStr(query,
@@ -4617,8 +4617,10 @@ dumpSubscription(Archive *fout, const SubscriptionInfo *subinfo)
 	if (strcmp(subinfo->subbinary, "t") == 0)
 		appendPQExpBufferStr(query, ", binary = true");
 
-	if (strcmp(subinfo->substream, "f") != 0)
+	if (strcmp(subinfo->substream, "t") == 0)
 		appendPQExpBufferStr(query, ", streaming = on");
+	else if (strcmp(subinfo->substream, "p") == 0)
+		appendPQExpBufferStr(query, ", streaming = parallel");
 
 	if (strcmp(subinfo->subtwophasestate, two_phase_disabled) != 0)
 		appendPQExpBufferStr(query, ", two_phase = on");
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index 7b98714f30..b99dddbea4 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -80,7 +80,8 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 	bool		subbinary;		/* True if the subscription wants the
 								 * publisher to send data in binary */
 
-	bool		substream;		/* Stream in-progress transactions. */
+	char		substream;		/* Stream in-progress transactions.
+								 * See SUBSTREAM_xxx constants. */
 
 	char		subtwophasestate;	/* Stream two-phase transactions */
 
@@ -124,7 +125,8 @@ typedef struct Subscription
 	bool		enabled;		/* Indicates if the subscription is enabled */
 	bool		binary;			/* Indicates if the subscription wants data in
 								 * binary format */
-	bool		stream;			/* Allow streaming in-progress transactions. */
+	char		stream;			/* Allow streaming in-progress transactions.
+								 * See SUBSTREAM_xxx constants. */
 	char		twophasestate;	/* Allow streaming two-phase transactions */
 	bool		disableonerr;	/* Indicates if the subscription should be
 								 * automatically disabled if a worker error
@@ -137,6 +139,21 @@ typedef struct Subscription
 								 * specified origin */
 } Subscription;
 
+/* Disallow streaming in-progress transactions. */
+#define SUBSTREAM_OFF 'f'
+
+/*
+ * Streaming in-progress transactions are written to a temporary file and
+ * applied only after the transaction is committed on upstream.
+ */
+#define SUBSTREAM_ON 't'
+
+/*
+ * Streaming in-progress transactions are applied immediately via a parallel
+ * apply worker.
+ */
+#define SUBSTREAM_PARALLEL 'p'
+
 extern Subscription *GetSubscription(Oid subid, bool missing_ok);
 extern void FreeSubscription(Subscription *sub);
 extern void DisableSubscription(Oid subid);
diff --git a/src/include/commands/defrem.h b/src/include/commands/defrem.h
index 56d2bb6616..f6ba5ffc01 100644
--- a/src/include/commands/defrem.h
+++ b/src/include/commands/defrem.h
@@ -154,6 +154,7 @@ extern List *defGetQualifiedName(DefElem *def);
 extern TypeName *defGetTypeName(DefElem *def);
 extern int	defGetTypeLength(DefElem *def);
 extern List *defGetStringList(DefElem *def);
+extern char defGetStreamingMode(DefElem *def);
 extern void errorConflictingDefElem(DefElem *defel, ParseState *pstate) pg_attribute_noreturn();
 
 #endif							/* DEFREM_H */
diff --git a/src/include/nodes/pg_list.h b/src/include/nodes/pg_list.h
index a6e04d04a3..c4253a772f 100644
--- a/src/include/nodes/pg_list.h
+++ b/src/include/nodes/pg_list.h
@@ -322,6 +322,17 @@ list_nth_oid(const List *list, int n)
 	return lfirst_oid(list_nth_cell(list, n));
 }
 
+/*
+ * Return the TransactionId value contained in the n'th element of the
+ * specified list.
+ */
+static inline TransactionId
+list_nth_xid(const List *list, int n)
+{
+	Assert(IsA(list, XidList));
+	return lfirst_xid(list_nth_cell(list, n));
+}
+
 #define list_nth_node(type,list,n)	castNode(type, list_nth(list, n))
 
 /*
diff --git a/src/include/replication/logicallauncher.h b/src/include/replication/logicallauncher.h
index f1e2821e25..d513ef533a 100644
--- a/src/include/replication/logicallauncher.h
+++ b/src/include/replication/logicallauncher.h
@@ -14,6 +14,7 @@
 
 extern PGDLLIMPORT int max_logical_replication_workers;
 extern PGDLLIMPORT int max_sync_workers_per_subscription;
+extern PGDLLIMPORT int max_parallel_apply_workers_per_subscription;
 
 extern void ApplyLauncherRegister(void);
 extern void ApplyLauncherMain(Datum main_arg);
diff --git a/src/include/replication/logicalproto.h b/src/include/replication/logicalproto.h
index a771ab8ff3..520f837473 100644
--- a/src/include/replication/logicalproto.h
+++ b/src/include/replication/logicalproto.h
@@ -32,12 +32,17 @@
  *
  * LOGICALREP_PROTO_TWOPHASE_VERSION_NUM is the minimum protocol version with
  * support for two-phase commit decoding (at prepare time). Introduced in PG15.
+ *
+ * LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM is the minimum protocol version
+ * where we support applying large streaming transactions in parallel.
+ * Introduced in PG16.
  */
 #define LOGICALREP_PROTO_MIN_VERSION_NUM 1
 #define LOGICALREP_PROTO_VERSION_NUM 1
 #define LOGICALREP_PROTO_STREAM_VERSION_NUM 2
 #define LOGICALREP_PROTO_TWOPHASE_VERSION_NUM 3
-#define LOGICALREP_PROTO_MAX_VERSION_NUM LOGICALREP_PROTO_TWOPHASE_VERSION_NUM
+#define LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM 4
+#define LOGICALREP_PROTO_MAX_VERSION_NUM LOGICALREP_PROTO_STREAM_PARALLEL_VERSION_NUM
 
 /*
  * Logical message types
@@ -175,6 +180,17 @@ typedef struct LogicalRepRollbackPreparedTxnData
 	char		gid[GIDSIZE];
 } LogicalRepRollbackPreparedTxnData;
 
+/*
+ * Transaction protocol information for stream abort.
+ */
+typedef struct LogicalRepStreamAbortData
+{
+	TransactionId xid;
+	TransactionId subxid;
+	XLogRecPtr	abort_lsn;
+	TimestampTz abort_time;
+} LogicalRepStreamAbortData;
+
 extern void logicalrep_write_begin(StringInfo out, ReorderBufferTXN *txn);
 extern void logicalrep_read_begin(StringInfo in,
 								  LogicalRepBeginData *begin_data);
@@ -246,9 +262,13 @@ extern void logicalrep_write_stream_commit(StringInfo out, ReorderBufferTXN *txn
 extern TransactionId logicalrep_read_stream_commit(StringInfo out,
 												   LogicalRepCommitData *commit_data);
 extern void logicalrep_write_stream_abort(StringInfo out, TransactionId xid,
-										  TransactionId subxid);
-extern void logicalrep_read_stream_abort(StringInfo in, TransactionId *xid,
-										 TransactionId *subxid);
+										  TransactionId subxid,
+										  XLogRecPtr abort_lsn,
+										  TimestampTz abort_time,
+										  bool abort_info);
+extern void logicalrep_read_stream_abort(StringInfo in,
+										 LogicalRepStreamAbortData *abort_data,
+										 bool read_abort_lsn);
 extern char *logicalrep_message_type(LogicalRepMsgType action);
 
 #endif							/* LOGICAL_PROTO_H */
diff --git a/src/include/replication/logicalworker.h b/src/include/replication/logicalworker.h
index cd1b6e8afc..96d7e81b06 100644
--- a/src/include/replication/logicalworker.h
+++ b/src/include/replication/logicalworker.h
@@ -12,8 +12,14 @@
 #ifndef LOGICALWORKER_H
 #define LOGICALWORKER_H
 
+extern PGDLLIMPORT volatile bool ParallelApplyMessagePending;
+
 extern void ApplyWorkerMain(Datum main_arg);
+extern void ParallelApplyWorkerMain(Datum main_arg);
 
 extern bool IsLogicalWorker(void);
+extern bool IsLogicalParallelApplyWorker(void);
+extern void HandleParallelApplyMessageInterrupt(void);
+extern void HandleParallelApplyMessages(void);
 
 #endif							/* LOGICALWORKER_H */
diff --git a/src/include/replication/pgoutput.h b/src/include/replication/pgoutput.h
index 02027550e2..3c30da8205 100644
--- a/src/include/replication/pgoutput.h
+++ b/src/include/replication/pgoutput.h
@@ -26,7 +26,7 @@ typedef struct PGOutputData
 	List	   *publication_names;
 	List	   *publications;
 	bool		binary;
-	bool		streaming;
+	char		streaming;
 	bool		messages;
 	bool		two_phase;
 	char	   *origin;
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index 8695901ba7..a74b616eff 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -301,6 +301,7 @@ typedef struct ReorderBufferTXN
 	{
 		TimestampTz commit_time;
 		TimestampTz prepare_time;
+		TimestampTz abort_time;
 	}			xact_time;
 
 	/*
@@ -658,9 +659,11 @@ extern void ReorderBufferFinishPrepared(ReorderBuffer *rb, TransactionId xid,
 extern void ReorderBufferAssignChild(ReorderBuffer *, TransactionId, TransactionId, XLogRecPtr commit_lsn);
 extern void ReorderBufferCommitChild(ReorderBuffer *, TransactionId, TransactionId,
 									 XLogRecPtr commit_lsn, XLogRecPtr end_lsn);
-extern void ReorderBufferAbort(ReorderBuffer *, TransactionId, XLogRecPtr lsn);
+extern void ReorderBufferAbort(ReorderBuffer *, TransactionId, XLogRecPtr lsn,
+							   TimestampTz abort_time);
 extern void ReorderBufferAbortOld(ReorderBuffer *, TransactionId xid);
-extern void ReorderBufferForget(ReorderBuffer *, TransactionId, XLogRecPtr lsn);
+extern void ReorderBufferForget(ReorderBuffer *, TransactionId, XLogRecPtr lsn,
+								TimestampTz abort_time);
 extern void ReorderBufferInvalidate(ReorderBuffer *, TransactionId, XLogRecPtr lsn);
 
 extern void ReorderBufferSetBaseSnapshot(ReorderBuffer *, TransactionId, XLogRecPtr lsn, struct SnapshotData *snap);
diff --git a/src/include/replication/walreceiver.h b/src/include/replication/walreceiver.h
index 9339f29303..454db48dbd 100644
--- a/src/include/replication/walreceiver.h
+++ b/src/include/replication/walreceiver.h
@@ -182,7 +182,7 @@ typedef struct
 			uint32		proto_version;	/* Logical protocol version */
 			List	   *publication_names;	/* String list of publications */
 			bool		binary; /* Ask publisher to use binary */
-			bool		streaming;	/* Streaming of large transactions */
+			char		streaming;	/* Streaming of large transactions */
 			bool		twophase;	/* Streaming of two-phase transactions at
 									 * prepare time */
 			char	   *origin; /* Only publish data originating from the
diff --git a/src/include/replication/worker_internal.h b/src/include/replication/worker_internal.h
index 901845abc2..aca3de72b7 100644
--- a/src/include/replication/worker_internal.h
+++ b/src/include/replication/worker_internal.h
@@ -17,8 +17,12 @@
 #include "access/xlogdefs.h"
 #include "catalog/pg_subscription.h"
 #include "datatype/timestamp.h"
+#include "miscadmin.h"
+#include "replication/logicalrelation.h"
 #include "storage/fileset.h"
 #include "storage/lock.h"
+#include "storage/shm_mq.h"
+#include "storage/shm_toc.h"
 #include "storage/spin.h"
 
 
@@ -60,6 +64,12 @@ typedef struct LogicalRepWorker
 	 */
 	FileSet    *stream_fileset;
 
+	/*
+	 * PID of leader apply worker if this slot is used for a parallel apply
+	 * worker, InvalidPid otherwise.
+	 */
+	pid_t			apply_leader_pid;
+
 	/* Stats. */
 	XLogRecPtr	last_lsn;
 	TimestampTz last_send_time;
@@ -68,9 +78,82 @@ typedef struct LogicalRepWorker
 	TimestampTz reply_time;
 } LogicalRepWorker;
 
+/* Struct for saving and restoring apply errcontext information */
+typedef struct ApplyErrorCallbackArg
+{
+	LogicalRepMsgType command;	/* 0 if invalid */
+	LogicalRepRelMapEntry *rel;
+
+	/* Remote node information */
+	int			remote_attnum;	/* -1 if invalid */
+	TransactionId remote_xid;
+	XLogRecPtr	finish_lsn;
+	char	   *origin_name;
+} ApplyErrorCallbackArg;
+
+/*
+ * Struct for sharing information between leader apply worker and parallel
+ * apply workers.
+ */
+typedef struct ParallelApplyWorkerShared
+{
+	slock_t		mutex;
+
+	/*
+	 * Flag used to ensure commit ordering.
+	 *
+	 * The parallel apply worker will set it to false after handling the
+	 * transaction finish commands while the apply leader will wait for it to
+	 * become false before proceeding in transaction finish commands (e.g.
+	 * STREAM_COMMIT/STREAM_ABORT/STREAM_PREPARE).
+	 */
+	bool	in_parallel_apply_xact;
+
+	/* Information from the corresponding LogicalRepWorker slot. */
+	uint16	logicalrep_worker_generation;
+
+	int		logicalrep_worker_slot_no;
+} ParallelApplyWorkerShared;
+
+/*
+ * Information which is used to manage the parallel apply worker.
+ */
+typedef struct ParallelApplyWorkerInfo
+{
+	shm_mq_handle			*mq_handle;
+
+	/*
+	 * The queue used to transfer messages from the parallel apply worker to
+	 * the leader apply worker. NULL if the parallel apply worker exited
+	 * cleanly.
+	 */
+	shm_mq_handle			*error_mq_handle;
+
+	dsm_segment				*dsm_seg;
+
+	/*
+	 * Indicates whether the worker is available to be used for parallel apply
+	 * transaction?
+	 */
+	bool					in_use;
+
+	ParallelApplyWorkerShared	*shared;
+} ParallelApplyWorkerInfo;
+
 /* Main memory context for apply worker. Permanent during worker lifetime. */
 extern PGDLLIMPORT MemoryContext ApplyContext;
 
+extern PGDLLIMPORT MemoryContext ApplyMessageContext;
+
+extern PGDLLIMPORT ErrorContextCallback	*apply_error_context_stack;
+extern PGDLLIMPORT ApplyErrorCallbackArg apply_error_callback_arg;
+
+extern PGDLLIMPORT bool MySubscriptionValid;
+
+extern PGDLLIMPORT ParallelApplyWorkerShared *MyParallelShared;
+
+extern PGDLLIMPORT List *subxactlist;
+
 /* libpqreceiver connection */
 extern PGDLLIMPORT struct WalReceiverConn *LogRepWorkerWalRcvConn;
 
@@ -79,18 +162,23 @@ extern PGDLLIMPORT Subscription *MySubscription;
 extern PGDLLIMPORT LogicalRepWorker *MyLogicalRepWorker;
 
 extern PGDLLIMPORT bool in_remote_transaction;
+extern PGDLLIMPORT TransactionId stream_xid;
+extern PGDLLIMPORT ParallelApplyWorkerInfo *stream_apply_worker;
 
 extern void logicalrep_worker_attach(int slot);
 extern LogicalRepWorker *logicalrep_worker_find(Oid subid, Oid relid,
 												bool only_running);
 extern List *logicalrep_workers_find(Oid subid, bool only_running);
-extern void logicalrep_worker_launch(Oid dbid, Oid subid, const char *subname,
-									 Oid userid, Oid relid);
+extern bool logicalrep_worker_launch(Oid dbid, Oid subid, const char *subname,
+									 Oid userid, Oid relid,
+									 dsm_handle subworker_dsm);
 extern void logicalrep_worker_stop(Oid subid, Oid relid);
+extern void logicalrep_worker_stop_by_slot(int slot_no, uint16 generation);
 extern void logicalrep_worker_wakeup(Oid subid, Oid relid);
 extern void logicalrep_worker_wakeup_ptr(LogicalRepWorker *worker);
 
 extern int	logicalrep_sync_worker_count(Oid subid);
+extern int	logicalrep_parallel_apply_worker_count(Oid subid);
 
 extern void ReplicationOriginNameForTablesync(Oid suboid, Oid relid,
 											  char *originname, int szorgname);
@@ -103,10 +191,48 @@ extern void process_syncing_tables(XLogRecPtr current_lsn);
 extern void invalidate_syncing_table_states(Datum arg, int cacheid,
 											uint32 hashvalue);
 
+extern void UpdateWorkerStats(XLogRecPtr last_lsn, TimestampTz send_time,
+							  bool reply);
+
+extern void apply_dispatch(StringInfo s);
+
+extern void InitializeApplyWorker(void);
+
+/* Function for apply error callback */
+extern void apply_error_callback(void *arg);
+
+extern void subscription_change_cb(Datum arg, int cacheid, uint32 hashvalue);
+
+/* Parallel apply worker setup and interactions */
+extern void parallel_apply_start_worker(TransactionId xid);
+extern ParallelApplyWorkerInfo *parallel_apply_find_worker(TransactionId xid);
+extern void parallel_apply_set_in_xact(ParallelApplyWorkerShared *wshared,
+									   bool in_xact);
+extern void parallel_apply_free_worker(ParallelApplyWorkerInfo *winfo,
+									   TransactionId xid);
+extern void parallel_apply_wait_for_xact_finish(ParallelApplyWorkerInfo *winfo);
+extern void parallel_apply_send_data(ParallelApplyWorkerInfo *winfo, Size nbytes,
+									 const void *data);
+
+extern void parallel_apply_subxact_info_add(TransactionId current_xid);
+extern void parallel_apply_stream_abort(LogicalRepStreamAbortData *abort_data);
+extern void parallel_apply_savepoint_name(Oid suboid, Oid relid,
+										  char *spname, int szsp);
+extern void parallel_apply_replorigin_setup(void);
+extern void parallel_apply_replorigin_reset(void);
+
+#define isParallelApplyWorker(worker) (worker->apply_leader_pid != InvalidPid)
+
 static inline bool
 am_tablesync_worker(void)
 {
 	return OidIsValid(MyLogicalRepWorker->relid);
 }
 
+static inline bool
+am_parallel_apply_worker(void)
+{
+	return isParallelApplyWorker(MyLogicalRepWorker);
+}
+
 #endif							/* WORKER_INTERNAL_H */
diff --git a/src/include/storage/procsignal.h b/src/include/storage/procsignal.h
index ee636900f3..528ef73199 100644
--- a/src/include/storage/procsignal.h
+++ b/src/include/storage/procsignal.h
@@ -35,6 +35,7 @@ typedef enum
 	PROCSIG_WALSND_INIT_STOPPING,	/* ask walsenders to prepare for shutdown  */
 	PROCSIG_BARRIER,			/* global barrier interrupt  */
 	PROCSIG_LOG_MEMORY_CONTEXT, /* ask backend to log the memory contexts */
+	PROCSIG_PARALLEL_APPLY_MESSAGE,	/* Message from parallel apply workers */
 
 	/* Recovery conflict reasons */
 	PROCSIG_RECOVERY_CONFLICT_DATABASE,
diff --git a/src/include/utils/wait_event.h b/src/include/utils/wait_event.h
index 6f2d5612e0..b2cdd554e1 100644
--- a/src/include/utils/wait_event.h
+++ b/src/include/utils/wait_event.h
@@ -105,6 +105,7 @@ typedef enum
 	WAIT_EVENT_HASH_GROW_BUCKETS_ALLOCATE,
 	WAIT_EVENT_HASH_GROW_BUCKETS_ELECT,
 	WAIT_EVENT_HASH_GROW_BUCKETS_REINSERT,
+	WAIT_EVENT_LOGICAL_PARALLEL_APPLY_STATE_CHANGE,
 	WAIT_EVENT_LOGICAL_SYNC_DATA,
 	WAIT_EVENT_LOGICAL_SYNC_STATE_CHANGE,
 	WAIT_EVENT_MQ_INTERNAL,
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
index ef0ebf96b9..99b9e867e4 100644
--- a/src/test/regress/expected/subscription.out
+++ b/src/test/regress/expected/subscription.out
@@ -217,9 +217,9 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 (1 row)
 
 DROP SUBSCRIPTION regress_testsub;
--- fail - streaming must be boolean
+-- fail - streaming must be boolean or 'parallel'
 CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, streaming = foo);
-ERROR:  streaming requires a Boolean value
+ERROR:  streaming requires a Boolean value or "parallel"
 -- now it works
 CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, streaming = true);
 WARNING:  tables were not subscribed, you will have to run ALTER SUBSCRIPTION ... REFRESH PUBLICATION to subscribe the tables
@@ -230,6 +230,14 @@ WARNING:  tables were not subscribed, you will have to run ALTER SUBSCRIPTION ..
  regress_testsub | regress_subscription_user | f       | {testpub}   | f      | t         | d                | f                | any    | off                | dbname=regress_doesnotexist | 0/0
 (1 row)
 
+ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
+\dRs+
+                                                                                         List of subscriptions
+      Name       |           Owner           | Enabled | Publication | Binary | Streaming | Two-phase commit | Disable on error | Origin | Synchronous commit |          Conninfo           | Skip LSN 
+-----------------+---------------------------+---------+-------------+--------+-----------+------------------+------------------+--------+--------------------+-----------------------------+----------
+ regress_testsub | regress_subscription_user | f       | {testpub}   | f      | p         | d                | f                | any    | off                | dbname=regress_doesnotexist | 0/0
+(1 row)
+
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 \dRs+
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
index 4425fafc46..ed148e4bd4 100644
--- a/src/test/regress/sql/subscription.sql
+++ b/src/test/regress/sql/subscription.sql
@@ -156,7 +156,7 @@ ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 
 DROP SUBSCRIPTION regress_testsub;
 
--- fail - streaming must be boolean
+-- fail - streaming must be boolean or 'parallel'
 CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUBLICATION testpub WITH (connect = false, streaming = foo);
 
 -- now it works
@@ -164,6 +164,10 @@ CREATE SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist' PUB
 
 \dRs+
 
+ALTER SUBSCRIPTION regress_testsub SET (streaming = parallel);
+
+\dRs+
+
 ALTER SUBSCRIPTION regress_testsub SET (streaming = false);
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = NONE);
 
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 5b3b305963..d205aed082 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1471,6 +1471,7 @@ LogicalRepRelId
 LogicalRepRelMapEntry
 LogicalRepRelation
 LogicalRepRollbackPreparedTxnData
+LogicalRepStreamAbortData
 LogicalRepTupleData
 LogicalRepTyp
 LogicalRepWorker
@@ -1662,6 +1663,9 @@ OverrideStackEntry
 OverridingKind
 PACE_HEADER
 PACL
+ParallelApplyWorkerEntry
+ParallelApplyWorkerInfo
+ParallelApplyWorkerShared
 PATH
 PBOOL
 PCtxtHandle
@@ -2783,6 +2787,7 @@ TransactionStmtKind
 TransformInfo
 TransformJsonStringValuesState
 TransitionCaptureState
+TransApplyAction
 TrgmArc
 TrgmArcInfo
 TrgmBound
-- 
2.23.0.windows.1



  [application/octet-stream] v29-0002-Test-streaming-parallel-option-in-tap-test.patch (74.5K, ../OS3PR01MB6275F145878B4A44586C46CE9E499@OS3PR01MB6275.jpnprd01.prod.outlook.com/3-v29-0002-Test-streaming-parallel-option-in-tap-test.patch)
  download | inline diff:
From 192f344a090967c85dfc7c958e229ca0260b890e Mon Sep 17 00:00:00 2001
From: "shiy.fnst" <[email protected]>
Date: Fri, 13 May 2022 14:50:30 +0800
Subject: [PATCH v29 2/5] Test streaming parallel option in tap test

Change all TAP tests using the SUBSCRIPTION "streaming" parameter, so they
now test both 'on' and 'parallel' values.
---
 src/test/subscription/t/015_stream.pl         | 231 +++++---
 src/test/subscription/t/016_stream_subxact.pl | 142 +++--
 src/test/subscription/t/017_stream_ddl.pl     | 220 ++++---
 .../t/018_stream_subxact_abort.pl             | 232 +++++---
 .../t/019_stream_subxact_ddl_abort.pl         | 133 ++++-
 .../subscription/t/022_twophase_cascade.pl    | 393 ++++++++-----
 .../subscription/t/023_twophase_stream.pl     | 539 +++++++++++-------
 7 files changed, 1245 insertions(+), 645 deletions(-)

diff --git a/src/test/subscription/t/015_stream.pl b/src/test/subscription/t/015_stream.pl
index cbaa327e44..f0e12190ce 100644
--- a/src/test/subscription/t/015_stream.pl
+++ b/src/test/subscription/t/015_stream.pl
@@ -8,6 +8,148 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
+# Check the log that the streamed transaction was completed successfully
+# reported by parallel apply worker.
+sub check_parallel_log
+{
+	my ($node_subscriber, $offset, $is_parallel)= @_;
+	my $parallel_message = 'finished processing the transaction finish command';
+
+	if ($is_parallel)
+	{
+		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
+	}
+}
+
+# Encapsulate all the common test steps which are related to "streaming"
+# parameter so the same code can be run both for the streaming=on and
+# streaming=parallel cases.
+sub test_streaming
+{
+	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
+
+	# Interleave a pair of transactions, each exceeding the 64kB limit.
+	my $in  = '';
+	my $out = '';
+
+	my $offset = 0;
+
+	my $timer = IPC::Run::timeout($PostgreSQL::Test::Utils::timeout_default);
+
+	my $h = $node_publisher->background_psql('postgres', \$in, \$out, $timer,
+		on_error_stop => 0);
+
+	# If "streaming" parameter is specified as "parallel", we need to check
+	# that streamed transaction was applied using a parallel apply worker.
+	# We have to look for the DEBUG1 log messages about that, so bump up the
+	# log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = debug1");
+		$node_subscriber->reload;
+	}
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	$in .= q{
+	BEGIN;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
+	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+	DELETE FROM test_tab WHERE mod(a,3) = 0;
+	};
+	$h->pump_nb;
+
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(5001, 9999) s(i);
+	DELETE FROM test_tab WHERE a > 5000;
+	COMMIT;
+	});
+
+	$in .= q{
+	COMMIT;
+	\q
+	};
+	$h->finish;    # errors make the next test fail, so ignore them here
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	my $result =
+	  $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
+	is($result, qq(3334|3334|3334),
+		'check extra columns contain local defaults');
+
+	# Test the streaming in binary mode
+	$node_subscriber->safe_psql('postgres',
+		"ALTER SUBSCRIPTION tap_sub SET (binary = on)");
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# Insert, update and delete enough rows to exceed the 64kB limit.
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(5001, 10000) s(i);
+	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+	DELETE FROM test_tab WHERE mod(a,3) = 0;
+	COMMIT;
+	});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	$result =
+	  $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
+	is($result, qq(6667|6667|6667),
+		'check extra columns contain local defaults');
+
+	# Change the local values of the extra columns on the subscriber,
+	# update publisher, and check that subscriber retains the expected
+	# values. This is to ensure that non-streaming transactions behave
+	# properly after a streaming transaction.
+	$node_subscriber->safe_psql('postgres',
+		"UPDATE test_tab SET c = 'epoch'::timestamptz + 987654321 * interval '1s'"
+	);
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	$node_publisher->safe_psql('postgres',
+		"UPDATE test_tab SET b = md5(a::text)");
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(extract(epoch from c) = 987654321), count(d = 999) FROM test_tab"
+	);
+	is($result, qq(6667|6667|6667),
+		'check extra columns contain locally changed data');
+
+	# Cleanup the test data
+	$node_publisher->safe_psql('postgres',
+		"DELETE FROM test_tab WHERE (a > 2)");
+	$node_publisher->wait_for_catchup($appname);
+
+	# Reset the log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = warning");
+		$node_subscriber->reload;
+	}
+}
+
 # Create publisher node
 my $node_publisher = PostgreSQL::Test::Cluster->new('publisher');
 $node_publisher->init(allows_streaming => 'logical');
@@ -37,6 +179,10 @@ $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION tap_pub FOR TABLE test_tab");
 
 my $appname = 'tap_sub';
+
+################################
+# Test using streaming mode 'on'
+################################
 $node_subscriber->safe_psql('postgres',
 	"CREATE SUBSCRIPTION tap_sub CONNECTION '$publisher_connstr application_name=$appname' PUBLICATION tap_pub WITH (streaming = on)"
 );
@@ -49,82 +195,25 @@ my $result =
 	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
 is($result, qq(2|2|2), 'check initial data was copied to subscriber');
 
-# Interleave a pair of transactions, each exceeding the 64kB limit.
-my $in  = '';
-my $out = '';
-
-my $timer = IPC::Run::timeout($PostgreSQL::Test::Utils::timeout_default);
-
-my $h = $node_publisher->background_psql('postgres', \$in, \$out, $timer,
-	on_error_stop => 0);
-
-$in .= q{
-BEGIN;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
-UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-DELETE FROM test_tab WHERE mod(a,3) = 0;
-};
-$h->pump_nb;
-
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(5001, 9999) s(i);
-DELETE FROM test_tab WHERE a > 5000;
-COMMIT;
-});
-
-$in .= q{
-COMMIT;
-\q
-};
-$h->finish;    # errors make the next test fail, so ignore them here
-
-$node_publisher->wait_for_catchup($appname);
-
-$result =
-  $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
-is($result, qq(3334|3334|3334), 'check extra columns contain local defaults');
+test_streaming($node_publisher, $node_subscriber, $appname, 0);
 
-# Test the streaming in binary mode
-$node_subscriber->safe_psql('postgres',
-	"ALTER SUBSCRIPTION tap_sub SET (binary = on)");
-
-# Insert, update and delete enough rows to exceed the 64kB limit.
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(5001, 10000) s(i);
-UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-DELETE FROM test_tab WHERE mod(a,3) = 0;
-COMMIT;
-});
-
-$node_publisher->wait_for_catchup($appname);
-
-$result =
-  $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
-is($result, qq(6667|6667|6667), 'check extra columns contain local defaults');
+######################################
+# Test using streaming mode 'parallel'
+######################################
+my $oldpid = $node_publisher->safe_psql('postgres',
+	"SELECT pid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
+);
 
-# Change the local values of the extra columns on the subscriber,
-# update publisher, and check that subscriber retains the expected
-# values. This is to ensure that non-streaming transactions behave
-# properly after a streaming transaction.
 $node_subscriber->safe_psql('postgres',
-	"UPDATE test_tab SET c = 'epoch'::timestamptz + 987654321 * interval '1s'"
-);
-$node_publisher->safe_psql('postgres',
-	"UPDATE test_tab SET b = md5(a::text)");
+	"ALTER SUBSCRIPTION tap_sub SET(streaming = parallel, binary = off)");
 
-$node_publisher->wait_for_catchup($appname);
+$node_publisher->poll_query_until('postgres',
+	"SELECT pid != $oldpid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
+  )
+  or die
+  "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
 
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(extract(epoch from c) = 987654321), count(d = 999) FROM test_tab"
-);
-is($result, qq(6667|6667|6667),
-	'check extra columns contain locally changed data');
+test_streaming($node_publisher, $node_subscriber, $appname, 1);
 
 $node_subscriber->stop;
 $node_publisher->stop;
diff --git a/src/test/subscription/t/016_stream_subxact.pl b/src/test/subscription/t/016_stream_subxact.pl
index bc0a9cd053..9d7e8506c4 100644
--- a/src/test/subscription/t/016_stream_subxact.pl
+++ b/src/test/subscription/t/016_stream_subxact.pl
@@ -8,6 +8,93 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
+# Check the log that the streamed transaction was completed successfully
+# reported by parallel apply worker.
+sub check_parallel_log
+{
+	my ($node_subscriber, $offset, $is_parallel)= @_;
+	my $parallel_message = 'finished processing the transaction finish command';
+
+	if ($is_parallel)
+	{
+		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
+	}
+}
+
+# Encapsulate all the common test steps which are related to "streaming"
+# parameter so the same code can be run both for the streaming=on and
+# streaming=parallel cases.
+sub test_streaming
+{
+	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
+
+	my $offset = 0;
+
+	# If "streaming" parameter is specified as "parallel", we need to check
+	# that streamed transaction was applied using a parallel apply worker.
+	# We have to look for the DEBUG1 log messages about that, so bump up the
+	# log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = debug1");
+		$node_subscriber->reload;
+	}
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# Insert, update and delete enough rows to exceed 64kB limit.
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 500) s(i);
+	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+	DELETE FROM test_tab WHERE mod(a,3) = 0;
+	SAVEPOINT s1;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(501, 1000) s(i);
+	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+	DELETE FROM test_tab WHERE mod(a,3) = 0;
+	SAVEPOINT s2;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(1001, 1500) s(i);
+	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+	DELETE FROM test_tab WHERE mod(a,3) = 0;
+	SAVEPOINT s3;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(1501, 2000) s(i);
+	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+	DELETE FROM test_tab WHERE mod(a,3) = 0;
+	SAVEPOINT s4;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(2001, 2500) s(i);
+	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+	DELETE FROM test_tab WHERE mod(a,3) = 0;
+	COMMIT;
+	});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	my $result =
+	  $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
+	is($result, qq(1667|1667|1667),
+		'check data was copied to subscriber in streaming mode and extra columns contain local defaults'
+	);
+
+	# Cleanup the test data
+	$node_publisher->safe_psql('postgres',
+		"DELETE FROM test_tab WHERE (a > 2)");
+	$node_publisher->wait_for_catchup($appname);
+
+	# Reset the log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = warning");
+		$node_subscriber->reload;
+	}
+}
+
 # Create publisher node
 my $node_publisher = PostgreSQL::Test::Cluster->new('publisher');
 $node_publisher->init(allows_streaming => 'logical');
@@ -37,6 +124,10 @@ $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION tap_pub FOR TABLE test_tab");
 
 my $appname = 'tap_sub';
+
+################################
+# Test using streaming mode 'on'
+################################
 $node_subscriber->safe_psql('postgres',
 	"CREATE SUBSCRIPTION tap_sub CONNECTION '$publisher_connstr application_name=$appname' PUBLICATION tap_pub WITH (streaming = on)"
 );
@@ -49,41 +140,26 @@ my $result =
 	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
 is($result, qq(2|2|2), 'check initial data was copied to subscriber');
 
-# Insert, update and delete enough rows to exceed 64kB limit.
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(    3,  500) s(i);
-UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-DELETE FROM test_tab WHERE mod(a,3) = 0;
-SAVEPOINT s1;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(501,  1000) s(i);
-UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-DELETE FROM test_tab WHERE mod(a,3) = 0;
-SAVEPOINT s2;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(1001,  1500) s(i);
-UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-DELETE FROM test_tab WHERE mod(a,3) = 0;
-SAVEPOINT s3;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(1501,  2000) s(i);
-UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-DELETE FROM test_tab WHERE mod(a,3) = 0;
-SAVEPOINT s4;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(2001, 2500) s(i);
-UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-DELETE FROM test_tab WHERE mod(a,3) = 0;
-COMMIT;
-});
-
-$node_publisher->wait_for_catchup($appname);
-
-$result =
-  $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
-is($result, qq(1667|1667|1667),
-	'check data was copied to subscriber in streaming mode and extra columns contain local defaults'
+test_streaming($node_publisher, $node_subscriber, $appname, 0);
+
+######################################
+# Test using streaming mode 'parallel'
+######################################
+my $oldpid = $node_publisher->safe_psql('postgres',
+	"SELECT pid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
 );
 
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET(streaming = parallel)");
+
+$node_publisher->poll_query_until('postgres',
+	"SELECT pid != $oldpid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
+  )
+  or die
+  "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
+
+test_streaming($node_publisher, $node_subscriber, $appname, 1);
+
 $node_subscriber->stop;
 $node_publisher->stop;
 
diff --git a/src/test/subscription/t/017_stream_ddl.pl b/src/test/subscription/t/017_stream_ddl.pl
index 866f1512e4..f3c55704cf 100644
--- a/src/test/subscription/t/017_stream_ddl.pl
+++ b/src/test/subscription/t/017_stream_ddl.pl
@@ -8,6 +8,137 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
+# Check the log that the streamed transaction was completed successfully
+# reported by parallel apply worker.
+sub check_parallel_log
+{
+	my ($node_subscriber, $offset, $is_parallel)= @_;
+	my $parallel_message = 'finished processing the transaction finish command';
+
+	if ($is_parallel)
+	{
+		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
+	}
+}
+
+# Encapsulate all the common test steps which are related to "streaming"
+# parameter so the same code can be run both for the streaming=on and
+# streaming=parallel cases.
+sub test_streaming
+{
+	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
+
+	my $offset = 0;
+
+	# a small (non-streamed) transaction with DDL and DML
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab VALUES (3, md5(3::text));
+	ALTER TABLE test_tab ADD COLUMN c INT;
+	SAVEPOINT s1;
+	INSERT INTO test_tab VALUES (4, md5(4::text), -4);
+	COMMIT;
+	});
+
+	# If "streaming" parameter is specified as "parallel", we need to check
+	# that streamed transaction was applied using a parallel apply worker.
+	# We have to look for the DEBUG1 log messages about that, so bump up the
+	# log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = debug1");
+		$node_subscriber->reload;
+	}
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# large (streamed) transaction with DDL and DML
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab SELECT i, md5(i::text), -i FROM generate_series(5, 1000) s(i);
+	ALTER TABLE test_tab ADD COLUMN d INT;
+	SAVEPOINT s1;
+	INSERT INTO test_tab SELECT i, md5(i::text), -i, 2*i FROM generate_series(1001, 2000) s(i);
+	COMMIT;
+	});
+
+	# a small (non-streamed) transaction with DDL and DML
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab VALUES (2001, md5(2001::text), -2001, 2*2001);
+	ALTER TABLE test_tab ADD COLUMN e INT;
+	SAVEPOINT s1;
+	INSERT INTO test_tab VALUES (2002, md5(2002::text), -2002, 2*2002, -3*2002);
+	COMMIT;
+	});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	my $result =
+	  $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d), count(e) FROM test_tab");
+	is($result, qq(2002|1999|1002|1),
+		'check data was copied to subscriber in streaming mode and extra columns contain local defaults'
+	);
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# A large (streamed) transaction with DDL and DML. One of the DDL is performed
+	# after DML to ensure that we invalidate the schema sent for test_tab so that
+	# the next transaction has to send the schema again.
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab SELECT i, md5(i::text), -i, 2*i, -3*i FROM generate_series(2003,5000) s(i);
+	ALTER TABLE test_tab ADD COLUMN f INT;
+	COMMIT;
+	});
+
+	# A small transaction that won't get streamed. This is just to ensure that we
+	# send the schema again to reflect the last column added in the previous test.
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab SELECT i, md5(i::text), -i, 2*i, -3*i, 4*i FROM generate_series(5001,5005) s(i);
+	COMMIT;
+	});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d), count(e), count(f) FROM test_tab"
+	);
+	is($result, qq(5005|5002|4005|3004|5),
+		'check data was copied to subscriber for both streaming and non-streaming transactions'
+	);
+
+	# Cleanup the test data
+	$node_publisher->safe_psql(
+		'postgres', q{
+	DELETE FROM test_tab WHERE (a > 2);
+	ALTER TABLE test_tab DROP COLUMN c, DROP COLUMN d, DROP COLUMN e, DROP COLUMN f;
+	});
+	$node_publisher->wait_for_catchup($appname);
+
+	# Reset the log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = warning");
+		$node_subscriber->reload;
+	}
+}
+
 # Create publisher node
 my $node_publisher = PostgreSQL::Test::Cluster->new('publisher');
 $node_publisher->init(allows_streaming => 'logical');
@@ -37,6 +168,10 @@ $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION tap_pub FOR TABLE test_tab");
 
 my $appname = 'tap_sub';
+
+################################
+# Test using streaming mode 'on'
+################################
 $node_subscriber->safe_psql('postgres',
 	"CREATE SUBSCRIPTION tap_sub CONNECTION '$publisher_connstr application_name=$appname' PUBLICATION tap_pub WITH (streaming = on)"
 );
@@ -49,77 +184,26 @@ my $result =
 	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
 is($result, qq(2|0|0), 'check initial data was copied to subscriber');
 
-# a small (non-streamed) transaction with DDL and DML
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab VALUES (3, md5(3::text));
-ALTER TABLE test_tab ADD COLUMN c INT;
-SAVEPOINT s1;
-INSERT INTO test_tab VALUES (4, md5(4::text), -4);
-COMMIT;
-});
-
-# large (streamed) transaction with DDL and DML
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab SELECT i, md5(i::text), -i FROM generate_series(5, 1000) s(i);
-ALTER TABLE test_tab ADD COLUMN d INT;
-SAVEPOINT s1;
-INSERT INTO test_tab SELECT i, md5(i::text), -i, 2*i FROM generate_series(1001, 2000) s(i);
-COMMIT;
-});
-
-# a small (non-streamed) transaction with DDL and DML
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab VALUES (2001, md5(2001::text), -2001, 2*2001);
-ALTER TABLE test_tab ADD COLUMN e INT;
-SAVEPOINT s1;
-INSERT INTO test_tab VALUES (2002, md5(2002::text), -2002, 2*2002, -3*2002);
-COMMIT;
-});
-
-$node_publisher->wait_for_catchup($appname);
-
-$result =
-  $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d), count(e) FROM test_tab");
-is($result, qq(2002|1999|1002|1),
-	'check data was copied to subscriber in streaming mode and extra columns contain local defaults'
-);
+test_streaming($node_publisher, $node_subscriber, $appname, 0);
 
-# A large (streamed) transaction with DDL and DML. One of the DDL is performed
-# after DML to ensure that we invalidate the schema sent for test_tab so that
-# the next transaction has to send the schema again.
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab SELECT i, md5(i::text), -i, 2*i, -3*i FROM generate_series(2003,5000) s(i);
-ALTER TABLE test_tab ADD COLUMN f INT;
-COMMIT;
-});
-
-# A small transaction that won't get streamed. This is just to ensure that we
-# send the schema again to reflect the last column added in the previous test.
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab SELECT i, md5(i::text), -i, 2*i, -3*i, 4*i FROM generate_series(5001,5005) s(i);
-COMMIT;
-});
-
-$node_publisher->wait_for_catchup($appname);
-
-$result =
-  $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d), count(e), count(f) FROM test_tab");
-is($result, qq(5005|5002|4005|3004|5),
-	'check data was copied to subscriber for both streaming and non-streaming transactions'
+######################################
+# Test using streaming mode 'parallel'
+######################################
+my $oldpid = $node_publisher->safe_psql('postgres',
+	"SELECT pid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
 );
 
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET(streaming = parallel)");
+
+$node_publisher->poll_query_until('postgres',
+	"SELECT pid != $oldpid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
+  )
+  or die
+  "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
+
+test_streaming($node_publisher, $node_subscriber, $appname, 1);
+
 $node_subscriber->stop;
 $node_publisher->stop;
 
diff --git a/src/test/subscription/t/018_stream_subxact_abort.pl b/src/test/subscription/t/018_stream_subxact_abort.pl
index 551f16df6d..f74542c2e9 100644
--- a/src/test/subscription/t/018_stream_subxact_abort.pl
+++ b/src/test/subscription/t/018_stream_subxact_abort.pl
@@ -8,6 +8,144 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
+# Check the log that the streamed transaction was completed successfully
+# reported by parallel apply worker.
+sub check_parallel_log
+{
+	my ($node_subscriber, $offset, $is_parallel)= @_;
+	my $parallel_message = 'finished processing the transaction finish command';
+
+	if ($is_parallel)
+	{
+		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
+	}
+}
+
+# Encapsulate all the common test steps which are related to "streaming"
+# parameter so the same code can be run both for the streaming=on and
+# streaming=parallel cases.
+sub test_streaming
+{
+	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
+
+	my $offset = 0;
+
+	# If "streaming" parameter is specified as "parallel", we need to check
+	# that streamed transaction was applied using a parallel apply worker.
+	# We have to look for the DEBUG1 log messages about that, so bump up the
+	# log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = debug1");
+		$node_subscriber->reload;
+	}
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# large (streamed) transaction with DDL, DML and ROLLBACKs
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3,500) s(i);
+	SAVEPOINT s1;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(501,1000) s(i);
+	SAVEPOINT s2;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(1001,1500) s(i);
+	SAVEPOINT s3;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(1501,2000) s(i);
+	ROLLBACK TO s2;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(2001,2500) s(i);
+	ROLLBACK TO s1;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(2501,3000) s(i);
+	SAVEPOINT s4;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3001,3500) s(i);
+	SAVEPOINT s5;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3501,4000) s(i);
+	COMMIT;
+	});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	my $result =
+	  $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c) FROM test_tab");
+	is($result, qq(2000|0),
+		'check rollback to savepoint was reflected on subscriber and extra columns contain local defaults'
+	);
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# large (streamed) transaction with subscriber receiving out of order
+	# subtransaction ROLLBACKs
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(4001,4500) s(i);
+	SAVEPOINT s1;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(5001,5500) s(i);
+	SAVEPOINT s2;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(6001,6500) s(i);
+	SAVEPOINT s3;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(7001,7500) s(i);
+	RELEASE s2;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(8001,8500) s(i);
+	ROLLBACK TO s1;
+	COMMIT;
+	});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	$result =
+	  $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c) FROM test_tab");
+	is($result, qq(2500|0),
+		'check rollback to savepoint was reflected on subscriber');
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# large (streamed) transaction with subscriber receiving rollback
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(8501,9000) s(i);
+	SAVEPOINT s1;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(9001,9500) s(i);
+	SAVEPOINT s2;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(9501,10000) s(i);
+	ROLLBACK;
+	});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	$result =
+	  $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c) FROM test_tab");
+	is($result, qq(2500|0), 'check rollback was reflected on subscriber');
+
+	# Cleanup the test data
+	$node_publisher->safe_psql('postgres',
+		"DELETE FROM test_tab WHERE (a > 2)");
+	$node_publisher->wait_for_catchup($appname);
+
+	# Reset the log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = warning");
+		$node_subscriber->reload;
+	}
+}
+
 # Create publisher node
 my $node_publisher = PostgreSQL::Test::Cluster->new('publisher');
 $node_publisher->init(allows_streaming => 'logical');
@@ -36,6 +174,10 @@ $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION tap_pub FOR TABLE test_tab");
 
 my $appname = 'tap_sub';
+
+################################
+# Test using streaming mode 'on'
+################################
 $node_subscriber->safe_psql('postgres',
 	"CREATE SUBSCRIPTION tap_sub CONNECTION '$publisher_connstr application_name=$appname' PUBLICATION tap_pub WITH (streaming = on)"
 );
@@ -48,81 +190,25 @@ my $result =
 	"SELECT count(*), count(c) FROM test_tab");
 is($result, qq(2|0), 'check initial data was copied to subscriber');
 
-# large (streamed) transaction with DDL, DML and ROLLBACKs
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3,500) s(i);
-SAVEPOINT s1;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(501,1000) s(i);
-SAVEPOINT s2;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(1001,1500) s(i);
-SAVEPOINT s3;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(1501,2000) s(i);
-ROLLBACK TO s2;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(2001,2500) s(i);
-ROLLBACK TO s1;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(2501,3000) s(i);
-SAVEPOINT s4;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3001,3500) s(i);
-SAVEPOINT s5;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3501,4000) s(i);
-COMMIT;
-});
-
-$node_publisher->wait_for_catchup($appname);
-
-$result =
-  $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c) FROM test_tab");
-is($result, qq(2000|0),
-	'check rollback to savepoint was reflected on subscriber and extra columns contain local defaults'
+test_streaming($node_publisher, $node_subscriber, $appname, 0);
+
+######################################
+# Test using streaming mode 'parallel'
+######################################
+my $oldpid = $node_publisher->safe_psql('postgres',
+	"SELECT pid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
 );
 
-# large (streamed) transaction with subscriber receiving out of order
-# subtransaction ROLLBACKs
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(4001,4500) s(i);
-SAVEPOINT s1;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(5001,5500) s(i);
-SAVEPOINT s2;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(6001,6500) s(i);
-SAVEPOINT s3;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(7001,7500) s(i);
-RELEASE s2;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(8001,8500) s(i);
-ROLLBACK TO s1;
-COMMIT;
-});
-
-$node_publisher->wait_for_catchup($appname);
-
-$result =
-  $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c) FROM test_tab");
-is($result, qq(2500|0),
-	'check rollback to savepoint was reflected on subscriber');
-
-# large (streamed) transaction with subscriber receiving rollback
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(8501,9000) s(i);
-SAVEPOINT s1;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(9001,9500) s(i);
-SAVEPOINT s2;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(9501,10000) s(i);
-ROLLBACK;
-});
-
-$node_publisher->wait_for_catchup($appname);
-
-$result =
-  $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c) FROM test_tab");
-is($result, qq(2500|0), 'check rollback was reflected on subscriber');
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET(streaming = parallel)");
+
+$node_publisher->poll_query_until('postgres',
+	"SELECT pid != $oldpid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
+  )
+  or die
+  "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
+
+test_streaming($node_publisher, $node_subscriber, $appname, 1);
 
 $node_subscriber->stop;
 $node_publisher->stop;
diff --git a/src/test/subscription/t/019_stream_subxact_ddl_abort.pl b/src/test/subscription/t/019_stream_subxact_ddl_abort.pl
index 4d7da82b7a..b6f3a60682 100644
--- a/src/test/subscription/t/019_stream_subxact_ddl_abort.pl
+++ b/src/test/subscription/t/019_stream_subxact_ddl_abort.pl
@@ -9,6 +9,90 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
+# Check the log that the streamed transaction was completed successfully
+# reported by parallel apply worker.
+sub check_parallel_log
+{
+	my ($node_subscriber, $offset, $is_parallel)= @_;
+	my $parallel_message = 'finished processing the transaction finish command';
+
+	if ($is_parallel)
+	{
+		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
+	}
+}
+
+# Encapsulate all the common test steps which are related to "streaming"
+# parameter so the same code can be run both for the streaming=on and
+# streaming=parallel cases.
+sub test_streaming
+{
+	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
+
+	my $offset = 0;
+
+	# If "streaming" parameter is specified as "parallel", we need to check
+	# that streamed transaction was applied using a parallel apply worker.
+	# We have to look for the DEBUG1 log messages about that, so bump up the
+	# log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = debug1");
+		$node_subscriber->reload;
+	}
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# large (streamed) transaction with DDL, DML and ROLLBACKs
+	$node_publisher->safe_psql(
+		'postgres', q{
+	BEGIN;
+	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3,500) s(i);
+	ALTER TABLE test_tab ADD COLUMN c INT;
+	SAVEPOINT s1;
+	INSERT INTO test_tab SELECT i, md5(i::text), -i FROM generate_series(501,1000) s(i);
+	ALTER TABLE test_tab ADD COLUMN d INT;
+	SAVEPOINT s2;
+	INSERT INTO test_tab SELECT i, md5(i::text), -i, 2*i FROM generate_series(1001,1500) s(i);
+	ALTER TABLE test_tab ADD COLUMN e INT;
+	SAVEPOINT s3;
+	INSERT INTO test_tab SELECT i, md5(i::text), -i, 2*i, -3*i FROM generate_series(1501,2000) s(i);
+	ALTER TABLE test_tab DROP COLUMN c;
+	ROLLBACK TO s1;
+	INSERT INTO test_tab SELECT i, md5(i::text), i FROM generate_series(501,1000) s(i);
+	COMMIT;
+	});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	my $result =
+	  $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c) FROM test_tab");
+	is($result, qq(1000|500),
+		'check rollback to savepoint was reflected on subscriber and extra columns contain local defaults'
+	);
+
+	# Cleanup the test data
+	$node_publisher->safe_psql(
+		'postgres', q{
+	DELETE FROM test_tab WHERE (a > 2);
+	ALTER TABLE test_tab DROP COLUMN c;
+	});
+	$node_publisher->wait_for_catchup($appname);
+
+	# Reset the log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = warning");
+		$node_subscriber->reload;
+	}
+}
+
 # Create publisher node
 my $node_publisher = PostgreSQL::Test::Cluster->new('publisher');
 $node_publisher->init(allows_streaming => 'logical');
@@ -37,6 +121,10 @@ $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION tap_pub FOR TABLE test_tab");
 
 my $appname = 'tap_sub';
+
+################################
+# Test using streaming mode 'on'
+################################
 $node_subscriber->safe_psql('postgres',
 	"CREATE SUBSCRIPTION tap_sub CONNECTION '$publisher_connstr application_name=$appname' PUBLICATION tap_pub WITH (streaming = on)"
 );
@@ -49,35 +137,26 @@ my $result =
 	"SELECT count(*), count(c) FROM test_tab");
 is($result, qq(2|0), 'check initial data was copied to subscriber');
 
-# large (streamed) transaction with DDL, DML and ROLLBACKs
-$node_publisher->safe_psql(
-	'postgres', q{
-BEGIN;
-INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3,500) s(i);
-ALTER TABLE test_tab ADD COLUMN c INT;
-SAVEPOINT s1;
-INSERT INTO test_tab SELECT i, md5(i::text), -i FROM generate_series(501,1000) s(i);
-ALTER TABLE test_tab ADD COLUMN d INT;
-SAVEPOINT s2;
-INSERT INTO test_tab SELECT i, md5(i::text), -i, 2*i FROM generate_series(1001,1500) s(i);
-ALTER TABLE test_tab ADD COLUMN e INT;
-SAVEPOINT s3;
-INSERT INTO test_tab SELECT i, md5(i::text), -i, 2*i, -3*i FROM generate_series(1501,2000) s(i);
-ALTER TABLE test_tab DROP COLUMN c;
-ROLLBACK TO s1;
-INSERT INTO test_tab SELECT i, md5(i::text), i FROM generate_series(501,1000) s(i);
-COMMIT;
-});
-
-$node_publisher->wait_for_catchup($appname);
-
-$result =
-  $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c) FROM test_tab");
-is($result, qq(1000|500),
-	'check rollback to savepoint was reflected on subscriber and extra columns contain local defaults'
+test_streaming($node_publisher, $node_subscriber, $appname, 0);
+
+######################################
+# Test using streaming mode 'parallel'
+######################################
+my $oldpid = $node_publisher->safe_psql('postgres',
+	"SELECT pid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
 );
 
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET(streaming = parallel)");
+
+$node_publisher->poll_query_until('postgres',
+	"SELECT pid != $oldpid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
+  )
+  or die
+  "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
+
+test_streaming($node_publisher, $node_subscriber, $appname, 1);
+
 $node_subscriber->stop;
 $node_publisher->stop;
 
diff --git a/src/test/subscription/t/022_twophase_cascade.pl b/src/test/subscription/t/022_twophase_cascade.pl
index 7a797f37ba..3b5830a3b4 100644
--- a/src/test/subscription/t/022_twophase_cascade.pl
+++ b/src/test/subscription/t/022_twophase_cascade.pl
@@ -11,6 +11,238 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
+# Check the log that the streamed transaction was completed successfully
+# reported by parallel apply worker.
+sub check_parallel_log
+{
+	my ($node_subscriber, $offset, $streaming_mode)= @_;
+	my $parallel_message = 'finished processing the transaction finish command';
+
+	if ($streaming_mode eq 'parallel')
+	{
+		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
+	}
+}
+
+# Encapsulate all the common test steps which are related to "streaming" parameter
+# so the same code can be run both for the streaming=on and streaming=parallel
+# cases.
+sub test_streaming
+{
+	my ($node_A, $node_B, $node_C, $appname_B, $appname_C, $streaming_mode) =
+	  @_;
+
+	my $offset_B = 0;
+	my $offset_C = 0;
+
+	my $oldpid_B = $node_A->safe_psql(
+		'postgres', "
+		SELECT pid FROM pg_stat_replication
+		WHERE application_name = '$appname_B' AND state = 'streaming';");
+	my $oldpid_C = $node_B->safe_psql(
+		'postgres', "
+		SELECT pid FROM pg_stat_replication
+		WHERE application_name = '$appname_C' AND state = 'streaming';");
+
+	# Setup logical replication streaming mode
+
+	$node_B->safe_psql(
+		'postgres', "
+		ALTER SUBSCRIPTION tap_sub_B
+		SET (streaming = $streaming_mode);");
+	$node_C->safe_psql(
+		'postgres', "
+		ALTER SUBSCRIPTION tap_sub_C
+		SET (streaming = $streaming_mode)");
+
+	# Wait for subscribers to finish initialization
+
+	$node_A->poll_query_until(
+		'postgres', "
+		SELECT pid != $oldpid_B FROM pg_stat_replication
+		WHERE application_name = '$appname_B' AND state = 'streaming';"
+	) or die "Timed out while waiting for apply to restart";
+	$node_B->poll_query_until(
+		'postgres', "
+		SELECT pid != $oldpid_C FROM pg_stat_replication
+		WHERE application_name = '$appname_C' AND state = 'streaming';"
+	) or die "Timed out while waiting for apply to restart";
+
+	###############################
+	# Test 2PC PREPARE / COMMIT PREPARED.
+	# 1. Data is streamed as a 2PC transaction.
+	# 2. Then do commit prepared.
+	#
+	# Expect all data is replicated on subscriber(s) after the commit.
+	###############################
+
+	# If "streaming" parameter is specified as "parallel", we need to check
+	# that streamed transaction was prepared using a parallel apply worker.
+	# We have to look for the DEBUG1 log messages about that, so bump up the
+	# log verbosity.
+	if ($streaming_mode eq 'parallel')
+	{
+		$node_B->append_conf('postgresql.conf', "log_min_messages = debug1");
+		$node_B->reload;
+
+		$node_C->append_conf('postgresql.conf', "log_min_messages = debug1");
+		$node_C->reload;
+	}
+
+	# Check the subscriber log from now on.
+	$offset_B = -s $node_B->logfile;
+	$offset_C = -s $node_C->logfile;
+
+	# Insert, update and delete enough rows to exceed the 64kB limit.
+	# Then 2PC PREPARE
+	$node_A->safe_psql(
+		'postgres', q{
+		BEGIN;
+		INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
+		UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+		DELETE FROM test_tab WHERE mod(a,3) = 0;
+		PREPARE TRANSACTION 'test_prepared_tab';});
+
+	$node_A->wait_for_catchup($appname_B);
+	$node_B->wait_for_catchup($appname_C);
+
+	check_parallel_log($node_B, $offset_B, $streaming_mode);
+	check_parallel_log($node_C, $offset_C, $streaming_mode);
+
+	# check the transaction state is prepared on subscriber(s)
+	my $result =
+	  $node_B->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(1), 'transaction is prepared on subscriber B');
+	$result =
+	  $node_C->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(1), 'transaction is prepared on subscriber C');
+
+	# 2PC COMMIT
+	$node_A->safe_psql('postgres', "COMMIT PREPARED 'test_prepared_tab';");
+
+	$node_A->wait_for_catchup($appname_B);
+	$node_B->wait_for_catchup($appname_C);
+
+	# check that transaction was committed on subscriber(s)
+	$result = $node_B->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
+	is($result, qq(3334|3334|3334),
+		'Rows inserted by 2PC have committed on subscriber B, and extra columns have local defaults'
+	);
+	$result = $node_C->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
+	is($result, qq(3334|3334|3334),
+		'Rows inserted by 2PC have committed on subscriber C, and extra columns have local defaults'
+	);
+
+	# check the transaction state is ended on subscriber(s)
+	$result =
+	  $node_B->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(0), 'transaction is committed on subscriber B');
+	$result =
+	  $node_C->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(0), 'transaction is committed on subscriber C');
+
+	###############################
+	# Test 2PC PREPARE with a nested ROLLBACK TO SAVEPOINT.
+	# 0. Cleanup from previous test leaving only 2 rows.
+	# 1. Insert one more row.
+	# 2. Record a SAVEPOINT.
+	# 3. Data is streamed using 2PC.
+	# 4. Do rollback to SAVEPOINT prior to the streamed inserts.
+	# 5. Then COMMIT PREPARED.
+	#
+	# Expect data after the SAVEPOINT is aborted leaving only 3 rows (= 2 original + 1 from step 1).
+	###############################
+
+	# First, delete the data except for 2 rows (delete will be replicated)
+	$node_A->safe_psql('postgres', "DELETE FROM test_tab WHERE a > 2;");
+
+	# Check the subscriber log from now on.
+	$offset_B = -s $node_B->logfile;
+	$offset_C = -s $node_C->logfile;
+
+	# 2PC PREPARE with a nested ROLLBACK TO SAVEPOINT
+	$node_A->safe_psql(
+		'postgres', "
+		BEGIN;
+		INSERT INTO test_tab VALUES (9999, 'foobar');
+		SAVEPOINT sp_inner;
+		INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
+		UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+		DELETE FROM test_tab WHERE mod(a,3) = 0;
+		ROLLBACK TO SAVEPOINT sp_inner;
+		PREPARE TRANSACTION 'outer';
+		");
+
+	$node_A->wait_for_catchup($appname_B);
+	$node_B->wait_for_catchup($appname_C);
+
+	check_parallel_log($node_B, $offset_B, $streaming_mode);
+	check_parallel_log($node_C, $offset_C, $streaming_mode);
+
+	# check the transaction state prepared on subscriber(s)
+	$result =
+	  $node_B->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(1), 'transaction is prepared on subscriber B');
+	$result =
+	  $node_C->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(1), 'transaction is prepared on subscriber C');
+
+	# 2PC COMMIT
+	$node_A->safe_psql('postgres', "COMMIT PREPARED 'outer';");
+
+	$node_A->wait_for_catchup($appname_B);
+	$node_B->wait_for_catchup($appname_C);
+
+	# check the transaction state is ended on subscriber
+	$result =
+	  $node_B->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(0), 'transaction is ended on subscriber B');
+	$result =
+	  $node_C->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(0), 'transaction is ended on subscriber C');
+
+	# check inserts are visible at subscriber(s).
+	# All the streamed data (prior to the SAVEPOINT) should be rolled back.
+	# (9999, 'foobar') should be committed.
+	$result = $node_B->safe_psql('postgres',
+		"SELECT count(*) FROM test_tab where b = 'foobar';");
+	is($result, qq(1), 'Rows committed are present on subscriber B');
+	$result =
+	  $node_B->safe_psql('postgres', "SELECT count(*) FROM test_tab;");
+	is($result, qq(3), 'Rows committed are present on subscriber B');
+	$result = $node_C->safe_psql('postgres',
+		"SELECT count(*) FROM test_tab where b = 'foobar';");
+	is($result, qq(1), 'Rows committed are present on subscriber C');
+	$result =
+	  $node_C->safe_psql('postgres', "SELECT count(*) FROM test_tab;");
+	is($result, qq(3), 'Rows committed are present on subscriber C');
+
+	# Cleanup the test data
+	$node_A->safe_psql('postgres', "DELETE FROM test_tab WHERE a > 2;");
+	$node_A->wait_for_catchup($appname_B);
+	$node_B->wait_for_catchup($appname_C);
+
+	# Reset the log verbosity.
+	if ($streaming_mode eq 'parallel')
+	{
+		$node_B->append_conf('postgresql.conf', "log_min_messages = warning");
+		$node_B->reload;
+
+		$node_C->append_conf('postgresql.conf', "log_min_messages = warning");
+		$node_C->reload;
+	}
+}
+
 ###############################
 # Setup a cascade of pub/sub nodes.
 # node_A -> node_B -> node_C
@@ -260,160 +492,15 @@ is($result, qq(21), 'Rows committed are present on subscriber C');
 # 2PC + STREAMING TESTS
 # ---------------------
 
-my $oldpid_B = $node_A->safe_psql(
-	'postgres', "
-	SELECT pid FROM pg_stat_replication
-	WHERE application_name = '$appname_B' AND state = 'streaming';");
-my $oldpid_C = $node_B->safe_psql(
-	'postgres', "
-	SELECT pid FROM pg_stat_replication
-	WHERE application_name = '$appname_C' AND state = 'streaming';");
-
-# Setup logical replication (streaming = on)
-
-$node_B->safe_psql(
-	'postgres', "
-	ALTER SUBSCRIPTION tap_sub_B
-	SET (streaming = on);");
-$node_C->safe_psql(
-	'postgres', "
-	ALTER SUBSCRIPTION tap_sub_C
-	SET (streaming = on)");
-
-# Wait for subscribers to finish initialization
-
-$node_A->poll_query_until(
-	'postgres', "
-	SELECT pid != $oldpid_B FROM pg_stat_replication
-	WHERE application_name = '$appname_B' AND state = 'streaming';"
-) or die "Timed out while waiting for apply to restart";
-$node_B->poll_query_until(
-	'postgres', "
-	SELECT pid != $oldpid_C FROM pg_stat_replication
-	WHERE application_name = '$appname_C' AND state = 'streaming';"
-) or die "Timed out while waiting for apply to restart";
-
-###############################
-# Test 2PC PREPARE / COMMIT PREPARED.
-# 1. Data is streamed as a 2PC transaction.
-# 2. Then do commit prepared.
-#
-# Expect all data is replicated on subscriber(s) after the commit.
-###############################
-
-# Insert, update and delete enough rows to exceed the 64kB limit.
-# Then 2PC PREPARE
-$node_A->safe_psql(
-	'postgres', q{
-	BEGIN;
-	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
-	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-	DELETE FROM test_tab WHERE mod(a,3) = 0;
-	PREPARE TRANSACTION 'test_prepared_tab';});
-
-$node_A->wait_for_catchup($appname_B);
-$node_B->wait_for_catchup($appname_C);
+################################
+# Test using streaming mode 'on'
+################################
+test_streaming($node_A, $node_B, $node_C, $appname_B, $appname_C, 'on');
 
-# check the transaction state is prepared on subscriber(s)
-$result =
-  $node_B->safe_psql('postgres', "SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(1), 'transaction is prepared on subscriber B');
-$result =
-  $node_C->safe_psql('postgres', "SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(1), 'transaction is prepared on subscriber C');
-
-# 2PC COMMIT
-$node_A->safe_psql('postgres', "COMMIT PREPARED 'test_prepared_tab';");
-
-$node_A->wait_for_catchup($appname_B);
-$node_B->wait_for_catchup($appname_C);
-
-# check that transaction was committed on subscriber(s)
-$result = $node_B->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
-is($result, qq(3334|3334|3334),
-	'Rows inserted by 2PC have committed on subscriber B, and extra columns have local defaults'
-);
-$result = $node_C->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
-is($result, qq(3334|3334|3334),
-	'Rows inserted by 2PC have committed on subscriber C, and extra columns have local defaults'
-);
-
-# check the transaction state is ended on subscriber(s)
-$result =
-  $node_B->safe_psql('postgres', "SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(0), 'transaction is committed on subscriber B');
-$result =
-  $node_C->safe_psql('postgres', "SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(0), 'transaction is committed on subscriber C');
-
-###############################
-# Test 2PC PREPARE with a nested ROLLBACK TO SAVEPOINT.
-# 0. Cleanup from previous test leaving only 2 rows.
-# 1. Insert one more row.
-# 2. Record a SAVEPOINT.
-# 3. Data is streamed using 2PC.
-# 4. Do rollback to SAVEPOINT prior to the streamed inserts.
-# 5. Then COMMIT PREPARED.
-#
-# Expect data after the SAVEPOINT is aborted leaving only 3 rows (= 2 original + 1 from step 1).
-###############################
-
-# First, delete the data except for 2 rows (delete will be replicated)
-$node_A->safe_psql('postgres', "DELETE FROM test_tab WHERE a > 2;");
-
-# 2PC PREPARE with a nested ROLLBACK TO SAVEPOINT
-$node_A->safe_psql(
-	'postgres', "
-	BEGIN;
-	INSERT INTO test_tab VALUES (9999, 'foobar');
-	SAVEPOINT sp_inner;
-	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
-	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-	DELETE FROM test_tab WHERE mod(a,3) = 0;
-	ROLLBACK TO SAVEPOINT sp_inner;
-	PREPARE TRANSACTION 'outer';
-	");
-
-$node_A->wait_for_catchup($appname_B);
-$node_B->wait_for_catchup($appname_C);
-
-# check the transaction state prepared on subscriber(s)
-$result =
-  $node_B->safe_psql('postgres', "SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(1), 'transaction is prepared on subscriber B');
-$result =
-  $node_C->safe_psql('postgres', "SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(1), 'transaction is prepared on subscriber C');
-
-# 2PC COMMIT
-$node_A->safe_psql('postgres', "COMMIT PREPARED 'outer';");
-
-$node_A->wait_for_catchup($appname_B);
-$node_B->wait_for_catchup($appname_C);
-
-# check the transaction state is ended on subscriber
-$result =
-  $node_B->safe_psql('postgres', "SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(0), 'transaction is ended on subscriber B');
-$result =
-  $node_C->safe_psql('postgres', "SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(0), 'transaction is ended on subscriber C');
-
-# check inserts are visible at subscriber(s).
-# All the streamed data (prior to the SAVEPOINT) should be rolled back.
-# (9999, 'foobar') should be committed.
-$result = $node_B->safe_psql('postgres',
-	"SELECT count(*) FROM test_tab where b = 'foobar';");
-is($result, qq(1), 'Rows committed are present on subscriber B');
-$result = $node_B->safe_psql('postgres', "SELECT count(*) FROM test_tab;");
-is($result, qq(3), 'Rows committed are present on subscriber B');
-$result = $node_C->safe_psql('postgres',
-	"SELECT count(*) FROM test_tab where b = 'foobar';");
-is($result, qq(1), 'Rows committed are present on subscriber C');
-$result = $node_C->safe_psql('postgres', "SELECT count(*) FROM test_tab;");
-is($result, qq(3), 'Rows committed are present on subscriber C');
+######################################
+# Test using streaming mode 'parallel'
+######################################
+test_streaming($node_A, $node_B, $node_C, $appname_B, $appname_C, 'parallel');
 
 ###############################
 # check all the cleanup
diff --git a/src/test/subscription/t/023_twophase_stream.pl b/src/test/subscription/t/023_twophase_stream.pl
index 9b454106bd..29989156f8 100644
--- a/src/test/subscription/t/023_twophase_stream.pl
+++ b/src/test/subscription/t/023_twophase_stream.pl
@@ -8,6 +8,307 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
+# Check the log that the streamed transaction was completed successfully
+# reported by parallel apply worker.
+sub check_parallel_log
+{
+	my ($node_subscriber, $offset, $is_parallel)= @_;
+	my $parallel_message = 'finished processing the transaction finish command';
+
+	if ($is_parallel)
+	{
+		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
+	}
+}
+
+# Encapsulate all the common test steps which are related to "streaming"
+# parameter so the same code can be run both for the streaming=on and
+# streaming=parallel cases.
+sub test_streaming
+{
+	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
+
+	my $offset = 0;
+
+	###############################
+	# Test 2PC PREPARE / COMMIT PREPARED.
+	# 1. Data is streamed as a 2PC transaction.
+	# 2. Then do commit prepared.
+	#
+	# Expect all data is replicated on subscriber side after the commit.
+	###############################
+
+	# If "streaming" parameter is specified as "parallel", we need to check
+	# that streamed transaction was prepared using a parallel apply worker.
+	# We have to look for the DEBUG1 log messages about that, so bump up the
+	# log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = debug1");
+		$node_subscriber->reload;
+	}
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# check that 2PC gets replicated to subscriber
+	# Insert, update and delete enough rows to exceed the 64kB limit.
+	$node_publisher->safe_psql(
+		'postgres', q{
+		BEGIN;
+		INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
+		UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+		DELETE FROM test_tab WHERE mod(a,3) = 0;
+		PREPARE TRANSACTION 'test_prepared_tab';});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	# check that transaction is in prepared state on subscriber
+	my $result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(1), 'transaction is prepared on subscriber');
+
+	# 2PC transaction gets committed
+	$node_publisher->safe_psql('postgres',
+		"COMMIT PREPARED 'test_prepared_tab';");
+
+	$node_publisher->wait_for_catchup($appname);
+
+	# check that transaction is committed on subscriber
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
+	is($result, qq(3334|3334|3334),
+		'Rows inserted by 2PC have committed on subscriber, and extra columns contain local defaults'
+	);
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(0), 'transaction is committed on subscriber');
+
+	###############################
+	# Test 2PC PREPARE / ROLLBACK PREPARED.
+	# 1. Table is deleted back to 2 rows which are replicated on subscriber.
+	# 2. Data is streamed using 2PC.
+	# 3. Do rollback prepared.
+	#
+	# Expect data rolls back leaving only the original 2 rows.
+	###############################
+
+	# First, delete the data except for 2 rows (will be replicated)
+	$node_publisher->safe_psql('postgres',
+		"DELETE FROM test_tab WHERE a > 2;");
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# Then insert, update and delete enough rows to exceed the 64kB limit.
+	$node_publisher->safe_psql(
+		'postgres', q{
+		BEGIN;
+		INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
+		UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+		DELETE FROM test_tab WHERE mod(a,3) = 0;
+		PREPARE TRANSACTION 'test_prepared_tab';});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	# check that transaction is in prepared state on subscriber
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(1), 'transaction is prepared on subscriber');
+
+	# 2PC transaction gets aborted
+	$node_publisher->safe_psql('postgres',
+		"ROLLBACK PREPARED 'test_prepared_tab';");
+
+	$node_publisher->wait_for_catchup($appname);
+
+	# check that transaction is aborted on subscriber
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
+	is($result, qq(2|2|2),
+		'Rows inserted by 2PC are rolled back, leaving only the original 2 rows'
+	);
+
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(0), 'transaction is aborted on subscriber');
+
+	###############################
+	# Check that 2PC COMMIT PREPARED is decoded properly on crash restart.
+	# 1. insert, update and delete enough rows to exceed the 64kB limit.
+	# 2. Then server crashes before the 2PC transaction is committed.
+	# 3. After servers are restarted the pending transaction is committed.
+	#
+	# Expect all data is replicated on subscriber side after the commit.
+	# Note: both publisher and subscriber do crash/restart.
+	###############################
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	$node_publisher->safe_psql(
+		'postgres', q{
+		BEGIN;
+		INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
+		UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+		DELETE FROM test_tab WHERE mod(a,3) = 0;
+		PREPARE TRANSACTION 'test_prepared_tab';});
+
+	$node_subscriber->stop('immediate');
+	$node_publisher->stop('immediate');
+
+	$node_publisher->start;
+	$node_subscriber->start;
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	# commit post the restart
+	$node_publisher->safe_psql('postgres',
+		"COMMIT PREPARED 'test_prepared_tab';");
+	$node_publisher->wait_for_catchup($appname);
+
+	# check inserts are visible
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
+	is($result, qq(3334|3334|3334),
+		'Rows inserted by 2PC have committed on subscriber, and extra columns contain local defaults'
+	);
+
+	###############################
+	# Do INSERT after the PREPARE but before ROLLBACK PREPARED.
+	# 1. Table is deleted back to 2 rows which are replicated on subscriber.
+	# 2. Data is streamed using 2PC.
+	# 3. A single row INSERT is done which is after the PREPARE.
+	# 4. Then do a ROLLBACK PREPARED.
+	#
+	# Expect the 2PC data rolls back leaving only 3 rows on the subscriber
+	# (the original 2 + inserted 1).
+	###############################
+
+	# First, delete the data except for 2 rows (will be replicated)
+	$node_publisher->safe_psql('postgres',
+		"DELETE FROM test_tab WHERE a > 2;");
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# Then insert, update and delete enough rows to exceed the 64kB limit.
+	$node_publisher->safe_psql(
+		'postgres', q{
+		BEGIN;
+		INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
+		UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+		DELETE FROM test_tab WHERE mod(a,3) = 0;
+		PREPARE TRANSACTION 'test_prepared_tab';});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	# check that transaction is in prepared state on subscriber
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(1), 'transaction is prepared on subscriber');
+
+	# Insert a different record (now we are outside of the 2PC transaction)
+	# Note: the 2PC transaction still holds row locks so make sure this insert is for a separate primary key
+	$node_publisher->safe_psql('postgres',
+		"INSERT INTO test_tab VALUES (99999, 'foobar')");
+
+	# 2PC transaction gets aborted
+	$node_publisher->safe_psql('postgres',
+		"ROLLBACK PREPARED 'test_prepared_tab';");
+
+	$node_publisher->wait_for_catchup($appname);
+
+	# check that transaction is aborted on subscriber,
+	# but the extra INSERT outside of the 2PC still was replicated
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
+	is($result, qq(3|3|3),
+		'check the outside insert was copied to subscriber');
+
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(0), 'transaction is aborted on subscriber');
+
+	###############################
+	# Do INSERT after the PREPARE but before COMMIT PREPARED.
+	# 1. Table is deleted back to 2 rows which are replicated on subscriber.
+	# 2. Data is streamed using 2PC.
+	# 3. A single row INSERT is done which is after the PREPARE.
+	# 4. Then do a COMMIT PREPARED.
+	#
+	# Expect 2PC data + the extra row are on the subscriber
+	# (the 3334 + inserted 1 = 3335).
+	###############################
+
+	# First, delete the data except for 2 rows (will be replicated)
+	$node_publisher->safe_psql('postgres',
+		"DELETE FROM test_tab WHERE a > 2;");
+
+	# Check the subscriber log from now on.
+	$offset = -s $node_subscriber->logfile;
+
+	# Then insert, update and delete enough rows to exceed the 64kB limit.
+	$node_publisher->safe_psql(
+		'postgres', q{
+		BEGIN;
+		INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
+		UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
+		DELETE FROM test_tab WHERE mod(a,3) = 0;
+		PREPARE TRANSACTION 'test_prepared_tab';});
+
+	$node_publisher->wait_for_catchup($appname);
+
+	check_parallel_log($node_subscriber, $offset, $is_parallel);
+
+	# check that transaction is in prepared state on subscriber
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(1), 'transaction is prepared on subscriber');
+
+	# Insert a different record (now we are outside of the 2PC transaction)
+	# Note: the 2PC transaction still holds row locks so make sure this insert is for a separare primary key
+	$node_publisher->safe_psql('postgres',
+		"INSERT INTO test_tab VALUES (99999, 'foobar')");
+
+	# 2PC transaction gets committed
+	$node_publisher->safe_psql('postgres',
+		"COMMIT PREPARED 'test_prepared_tab';");
+
+	$node_publisher->wait_for_catchup($appname);
+
+	# check that transaction is committed on subscriber
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
+	is($result, qq(3335|3335|3335),
+		'Rows inserted by 2PC (as well as outside insert) have committed on subscriber, and extra columns contain local defaults'
+	);
+
+	$result = $node_subscriber->safe_psql('postgres',
+		"SELECT count(*) FROM pg_prepared_xacts;");
+	is($result, qq(0), 'transaction is committed on subscriber');
+
+	# Cleanup the test data
+	$node_publisher->safe_psql('postgres',
+		"DELETE FROM test_tab WHERE a > 2;");
+	$node_publisher->wait_for_catchup($appname);
+
+	# Reset the log verbosity.
+	if ($is_parallel)
+	{
+		$node_subscriber->append_conf('postgresql.conf',
+			"log_min_messages = warning");
+		$node_subscriber->reload;
+	}
+}
+
 ###############################
 # Setup
 ###############################
@@ -48,6 +349,10 @@ $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION tap_pub FOR TABLE test_tab");
 
 my $appname = 'tap_sub';
+
+################################
+# Test using streaming mode 'on'
+################################
 $node_subscriber->safe_psql(
 	'postgres', "
 	CREATE SUBSCRIPTION tap_sub
@@ -64,236 +369,30 @@ my $twophase_query =
 $node_subscriber->poll_query_until('postgres', $twophase_query)
   or die "Timed out while waiting for subscriber to enable twophase";
 
-###############################
 # Check initial data was copied to subscriber
-###############################
 my $result = $node_subscriber->safe_psql('postgres',
 	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
 is($result, qq(2|2|2), 'check initial data was copied to subscriber');
 
-###############################
-# Test 2PC PREPARE / COMMIT PREPARED.
-# 1. Data is streamed as a 2PC transaction.
-# 2. Then do commit prepared.
-#
-# Expect all data is replicated on subscriber side after the commit.
-###############################
+test_streaming($node_publisher, $node_subscriber, $appname, 0);
 
-# check that 2PC gets replicated to subscriber
-# Insert, update and delete enough rows to exceed the 64kB limit.
-$node_publisher->safe_psql(
-	'postgres', q{
-	BEGIN;
-	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
-	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-	DELETE FROM test_tab WHERE mod(a,3) = 0;
-	PREPARE TRANSACTION 'test_prepared_tab';});
-
-$node_publisher->wait_for_catchup($appname);
-
-# check that transaction is in prepared state on subscriber
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(1), 'transaction is prepared on subscriber');
-
-# 2PC transaction gets committed
-$node_publisher->safe_psql('postgres',
-	"COMMIT PREPARED 'test_prepared_tab';");
-
-$node_publisher->wait_for_catchup($appname);
-
-# check that transaction is committed on subscriber
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
-is($result, qq(3334|3334|3334),
-	'Rows inserted by 2PC have committed on subscriber, and extra columns contain local defaults'
+######################################
+# Test using streaming mode 'parallel'
+######################################
+my $oldpid = $node_publisher->safe_psql('postgres',
+	"SELECT pid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
 );
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(0), 'transaction is committed on subscriber');
-
-###############################
-# Test 2PC PREPARE / ROLLBACK PREPARED.
-# 1. Table is deleted back to 2 rows which are replicated on subscriber.
-# 2. Data is streamed using 2PC.
-# 3. Do rollback prepared.
-#
-# Expect data rolls back leaving only the original 2 rows.
-###############################
-
-# First, delete the data except for 2 rows (will be replicated)
-$node_publisher->safe_psql('postgres', "DELETE FROM test_tab WHERE a > 2;");
-
-# Then insert, update and delete enough rows to exceed the 64kB limit.
-$node_publisher->safe_psql(
-	'postgres', q{
-	BEGIN;
-	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
-	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-	DELETE FROM test_tab WHERE mod(a,3) = 0;
-	PREPARE TRANSACTION 'test_prepared_tab';});
 
-$node_publisher->wait_for_catchup($appname);
-
-# check that transaction is in prepared state on subscriber
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(1), 'transaction is prepared on subscriber');
-
-# 2PC transaction gets aborted
-$node_publisher->safe_psql('postgres',
-	"ROLLBACK PREPARED 'test_prepared_tab';");
-
-$node_publisher->wait_for_catchup($appname);
-
-# check that transaction is aborted on subscriber
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
-is($result, qq(2|2|2),
-	'Rows inserted by 2PC are rolled back, leaving only the original 2 rows');
-
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(0), 'transaction is aborted on subscriber');
-
-###############################
-# Check that 2PC COMMIT PREPARED is decoded properly on crash restart.
-# 1. insert, update and delete enough rows to exceed the 64kB limit.
-# 2. Then server crashes before the 2PC transaction is committed.
-# 3. After servers are restarted the pending transaction is committed.
-#
-# Expect all data is replicated on subscriber side after the commit.
-# Note: both publisher and subscriber do crash/restart.
-###############################
-
-$node_publisher->safe_psql(
-	'postgres', q{
-	BEGIN;
-	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
-	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-	DELETE FROM test_tab WHERE mod(a,3) = 0;
-	PREPARE TRANSACTION 'test_prepared_tab';});
-
-$node_subscriber->stop('immediate');
-$node_publisher->stop('immediate');
-
-$node_publisher->start;
-$node_subscriber->start;
-
-# commit post the restart
-$node_publisher->safe_psql('postgres',
-	"COMMIT PREPARED 'test_prepared_tab';");
-$node_publisher->wait_for_catchup($appname);
-
-# check inserts are visible
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
-is($result, qq(3334|3334|3334),
-	'Rows inserted by 2PC have committed on subscriber, and extra columns contain local defaults'
-);
-
-###############################
-# Do INSERT after the PREPARE but before ROLLBACK PREPARED.
-# 1. Table is deleted back to 2 rows which are replicated on subscriber.
-# 2. Data is streamed using 2PC.
-# 3. A single row INSERT is done which is after the PREPARE.
-# 4. Then do a ROLLBACK PREPARED.
-#
-# Expect the 2PC data rolls back leaving only 3 rows on the subscriber
-# (the original 2 + inserted 1).
-###############################
-
-# First, delete the data except for 2 rows (will be replicated)
-$node_publisher->safe_psql('postgres', "DELETE FROM test_tab WHERE a > 2;");
-
-# Then insert, update and delete enough rows to exceed the 64kB limit.
-$node_publisher->safe_psql(
-	'postgres', q{
-	BEGIN;
-	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
-	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-	DELETE FROM test_tab WHERE mod(a,3) = 0;
-	PREPARE TRANSACTION 'test_prepared_tab';});
-
-$node_publisher->wait_for_catchup($appname);
-
-# check that transaction is in prepared state on subscriber
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(1), 'transaction is prepared on subscriber');
-
-# Insert a different record (now we are outside of the 2PC transaction)
-# Note: the 2PC transaction still holds row locks so make sure this insert is for a separate primary key
-$node_publisher->safe_psql('postgres',
-	"INSERT INTO test_tab VALUES (99999, 'foobar')");
-
-# 2PC transaction gets aborted
-$node_publisher->safe_psql('postgres',
-	"ROLLBACK PREPARED 'test_prepared_tab';");
-
-$node_publisher->wait_for_catchup($appname);
-
-# check that transaction is aborted on subscriber,
-# but the extra INSERT outside of the 2PC still was replicated
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
-is($result, qq(3|3|3), 'check the outside insert was copied to subscriber');
-
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(0), 'transaction is aborted on subscriber');
-
-###############################
-# Do INSERT after the PREPARE but before COMMIT PREPARED.
-# 1. Table is deleted back to 2 rows which are replicated on subscriber.
-# 2. Data is streamed using 2PC.
-# 3. A single row INSERT is done which is after the PREPARE.
-# 4. Then do a COMMIT PREPARED.
-#
-# Expect 2PC data + the extra row are on the subscriber
-# (the 3334 + inserted 1 = 3335).
-###############################
-
-# First, delete the data except for 2 rows (will be replicated)
-$node_publisher->safe_psql('postgres', "DELETE FROM test_tab WHERE a > 2;");
-
-# Then insert, update and delete enough rows to exceed the 64kB limit.
-$node_publisher->safe_psql(
-	'postgres', q{
-	BEGIN;
-	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
-	UPDATE test_tab SET b = md5(b) WHERE mod(a,2) = 0;
-	DELETE FROM test_tab WHERE mod(a,3) = 0;
-	PREPARE TRANSACTION 'test_prepared_tab';});
-
-$node_publisher->wait_for_catchup($appname);
-
-# check that transaction is in prepared state on subscriber
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(1), 'transaction is prepared on subscriber');
-
-# Insert a different record (now we are outside of the 2PC transaction)
-# Note: the 2PC transaction still holds row locks so make sure this insert is for a separare primary key
-$node_publisher->safe_psql('postgres',
-	"INSERT INTO test_tab VALUES (99999, 'foobar')");
-
-# 2PC transaction gets committed
-$node_publisher->safe_psql('postgres',
-	"COMMIT PREPARED 'test_prepared_tab';");
-
-$node_publisher->wait_for_catchup($appname);
+$node_subscriber->safe_psql('postgres',
+	"ALTER SUBSCRIPTION tap_sub SET(streaming = parallel)");
 
-# check that transaction is committed on subscriber
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
-is($result, qq(3335|3335|3335),
-	'Rows inserted by 2PC (as well as outside insert) have committed on subscriber, and extra columns contain local defaults'
-);
+$node_publisher->poll_query_until('postgres',
+	"SELECT pid != $oldpid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
+  )
+  or die
+  "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
 
-$result = $node_subscriber->safe_psql('postgres',
-	"SELECT count(*) FROM pg_prepared_xacts;");
-is($result, qq(0), 'transaction is committed on subscriber');
+test_streaming($node_publisher, $node_subscriber, $appname, 1);
 
 ###############################
 # check all the cleanup
-- 
2.23.0.windows.1



  [application/octet-stream] v29-0003-Add-some-checks-before-using-parallel-apply-work.patch (49.8K, ../OS3PR01MB6275F145878B4A44586C46CE9E499@OS3PR01MB6275.jpnprd01.prod.outlook.com/4-v29-0003-Add-some-checks-before-using-parallel-apply-work.patch)
  download | inline diff:
From de7f01ecc0b8385d764d2c185fe68dfce3898eaf Mon Sep 17 00:00:00 2001
From: "houzj.fnst" <[email protected]>
Date: Wed, 10 Aug 2022 20:37:22 +0800
Subject: [PATCH v29 3/5] Add some checks before using parallel apply worker to
 apply changes

streaming=parallel mode has two requirements:
1) The unique column in the relation on the subscriber-side should also be the
unique column on the publisher-side;
2) There cannot be any non-immutable functions used by the subscriber-side
replicated table. Look for functions in the following places:
* a. Trigger functions
* b. Column default value expressions and domain constraints
* c. Constraint expressions
It is better to only check the foreign key when it is detected that the
publisher does not have the foreign key and the subscriber does. But this
requires the publisher to send more information. In addition, since foreign key
does not take effect in the subscriber's apply worker by default, it seems that
foreign key does not hit this ERROR frequently. So, only perform a simple check
based on the subscriber schema when checking non-immutable function uesd by
trigger.

Without these safety checks, the following scenario may occur:
The parallel apply worker locks a row when processing a streaming transaction,
after that the leader apply worker tries to lock the same row when processing
another non-streamed transaction. At this time, the leader apply worker waits
for the streaming transaction to complete and the lock to be released, it won't
send subsequent data of the streaming transaction to the parallel apply worker;
the parallel apply worker waits to receive the rest of streaming transaction
and can't finish this transaction. Now a deadlock has occurred, so both workers
will wait indefinitely.
---
 doc/src/sgml/ref/create_subscription.sgml     |   5 +
 .../replication/logical/applyparallelworker.c |  42 ++
 src/backend/replication/logical/proto.c       |  86 ++-
 src/backend/replication/logical/relation.c    | 195 ++++++
 src/backend/replication/logical/tablesync.c   |   1 +
 src/backend/replication/logical/worker.c      |  23 +-
 src/backend/utils/cache/typcache.c            |  17 +
 src/include/replication/logicalproto.h        |   1 +
 src/include/replication/logicalrelation.h     |  15 +
 src/include/replication/worker_internal.h     |   2 +
 src/include/utils/typcache.h                  |   2 +
 src/test/subscription/t/015_stream.pl         |   9 +-
 src/test/subscription/t/016_stream_subxact.pl |   9 +-
 .../subscription/t/022_twophase_cascade.pl    |   8 +
 .../subscription/t/023_twophase_stream.pl     |   9 +-
 .../t/032_streaming_parallel_safety.pl        | 609 ++++++++++++++++++
 src/tools/pgindent/typedefs.list              |   1 +
 17 files changed, 1019 insertions(+), 15 deletions(-)
 create mode 100644 src/test/subscription/t/032_streaming_parallel_safety.pl

diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index 175cce8506..ef256346b8 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -245,6 +245,11 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           transaction is committed. Note that if an error happens when
           applying changes in a parallel worker, the finish LSN of the
           remote transaction might not be reported in the server log.
+          There are two prerequisites for using <literal>parallel</literal>
+          mode: 1) the unique column in the table on the subscriber-side must
+          also be the unique column on the publisher-side; 2) there cannot be
+          any non-immutable functions used by the subscriber-side replicated
+          table.
          </para>
         </listitem>
        </varlistentry>
diff --git a/src/backend/replication/logical/applyparallelworker.c b/src/backend/replication/logical/applyparallelworker.c
index 2f771fc4a1..d64ae5fb26 100644
--- a/src/backend/replication/logical/applyparallelworker.c
+++ b/src/backend/replication/logical/applyparallelworker.c
@@ -1076,3 +1076,45 @@ parallel_apply_replorigin_reset(void)
 	if (started_tx)
 		CommitTransactionCommand();
 }
+
+/*
+ * Check if changes on this relation can be applied using a parallel apply
+ * worker.
+ *
+ * Although the commit order is maintained by only allowing one process to
+ * commit at a time, the access order to the relation has changed. This could
+ * cause unexpected problems when applying transactions using a parallel
+ * apply worker if the unique column on the replicated table is
+ * inconsistent with the publisher-side, or if the relation contains
+ * non-immutable functions.
+ */
+void
+parallel_apply_relation_check(LogicalRepRelMapEntry *rel)
+{
+	/* Skip if not the parallel apply worker */
+	if (!am_parallel_apply_worker())
+		return;
+
+	/*
+	 * Partition table checks are done later in function
+	 * apply_handle_tuple_routing.
+	 */
+	if (rel->localrel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+		return;
+
+	if (rel->parallel_apply_safety == PARALLEL_APPLY_SAFETY_UNKNOWN)
+		logicalrep_rel_mark_parallel_apply(rel);
+
+	if (rel->parallel_apply_safety == PARALLEL_APPLY_UNSAFE)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("cannot replicate target relation \"%s.%s\" using "
+						"subscription parameter %s",
+						rel->remoterel.nspname, rel->remoterel.relname,
+						"streaming = parallel"),
+				 errdetail("The unique column on subscriber is not the unique "
+						   "column on publisher or there is at least one "
+						   "non-immutable function."),
+				 errhint("Please change to use subscription parameter %s.",
+						"streaming = on")));
+}
diff --git a/src/backend/replication/logical/proto.c b/src/backend/replication/logical/proto.c
index 364d5d7c28..56a47b7dc1 100644
--- a/src/backend/replication/logical/proto.c
+++ b/src/backend/replication/logical/proto.c
@@ -23,7 +23,8 @@
 /*
  * Protocol message flags.
  */
-#define LOGICALREP_IS_REPLICA_IDENTITY 1
+#define ATTR_IS_REPLICA_IDENTITY	(1 << 0)
+#define ATTR_IS_UNIQUE				(1 << 1)
 
 #define MESSAGE_TRANSACTIONAL (1<<0)
 #define TRUNCATE_CASCADE		(1<<0)
@@ -40,6 +41,66 @@ static void logicalrep_read_tuple(StringInfo in, LogicalRepTupleData *tuple);
 static void logicalrep_write_namespace(StringInfo out, Oid nspid);
 static const char *logicalrep_read_namespace(StringInfo in);
 
+/*
+ * RelationGetUniqueKeyBitmap -- get a bitmap of unique attribute numbers
+ *
+ * This is similar to RelationGetIdentityKeyBitmap(), but returns a bitmap of
+ * index attribute numbers for all unique indexes.
+ */
+static Bitmapset *
+RelationGetUniqueKeyBitmap(Relation rel)
+{
+	List		   *indexoidlist = NIL;
+	ListCell	   *indexoidscan;
+	Bitmapset	   *attunique = NULL;
+
+	if (!rel->rd_rel->relhasindex)
+		return NULL;
+
+	indexoidlist = RelationGetIndexList(rel);
+
+	foreach(indexoidscan, indexoidlist)
+	{
+		Oid			indexoid = lfirst_oid(indexoidscan);
+		Relation	indexRel;
+		int			i;
+
+		/* Look up the description for index */
+		indexRel = RelationIdGetRelation(indexoid);
+
+		if (!RelationIsValid(indexRel))
+			elog(ERROR, "could not open relation with OID %u", indexoid);
+
+		if (!indexRel->rd_index->indisunique)
+		{
+			RelationClose(indexRel);
+			continue;
+		}
+
+		/* Add referenced attributes to attunique */
+		for (i = 0; i < indexRel->rd_index->indnatts; i++)
+		{
+			int attrnum = indexRel->rd_index->indkey.values[i];
+
+			/*
+			 * We don't include non-key columns into attunique
+			 * bitmaps. See RelationGetIndexAttrBitmap.
+			 */
+			if (attrnum != 0)
+			{
+				if (i < indexRel->rd_index->indnkeyatts &&
+					!bms_is_member(attrnum - FirstLowInvalidHeapAttributeNumber, attunique))
+					attunique = bms_add_member(attunique,
+											   attrnum - FirstLowInvalidHeapAttributeNumber);
+			}
+		}
+		RelationClose(indexRel);
+	}
+	list_free(indexoidlist);
+
+	return attunique;
+}
+
 /*
  * Check if a column is covered by a column list.
  *
@@ -933,7 +994,8 @@ logicalrep_write_attrs(StringInfo out, Relation rel, Bitmapset *columns)
 	TupleDesc	desc;
 	int			i;
 	uint16		nliveatts = 0;
-	Bitmapset  *idattrs = NULL;
+	Bitmapset  *idattrs = NULL,
+			   *attunique = NULL;
 	bool		replidentfull;
 
 	desc = RelationGetDescr(rel);
@@ -958,6 +1020,9 @@ logicalrep_write_attrs(StringInfo out, Relation rel, Bitmapset *columns)
 	if (!replidentfull)
 		idattrs = RelationGetIdentityKeyBitmap(rel);
 
+	/* fetch bitmap of UNIQUE attributes */
+	attunique = RelationGetUniqueKeyBitmap(rel);
+
 	/* send the attributes */
 	for (i = 0; i < desc->natts; i++)
 	{
@@ -974,7 +1039,11 @@ logicalrep_write_attrs(StringInfo out, Relation rel, Bitmapset *columns)
 		if (replidentfull ||
 			bms_is_member(att->attnum - FirstLowInvalidHeapAttributeNumber,
 						  idattrs))
-			flags |= LOGICALREP_IS_REPLICA_IDENTITY;
+			flags |= ATTR_IS_REPLICA_IDENTITY;
+
+		if (bms_is_member(att->attnum - FirstLowInvalidHeapAttributeNumber,
+						  attunique))
+			flags |= ATTR_IS_UNIQUE;
 
 		pq_sendbyte(out, flags);
 
@@ -989,6 +1058,7 @@ logicalrep_write_attrs(StringInfo out, Relation rel, Bitmapset *columns)
 	}
 
 	bms_free(idattrs);
+	bms_free(attunique);
 }
 
 /*
@@ -1001,7 +1071,8 @@ logicalrep_read_attrs(StringInfo in, LogicalRepRelation *rel)
 	int			natts;
 	char	  **attnames;
 	Oid		   *atttyps;
-	Bitmapset  *attkeys = NULL;
+	Bitmapset  *attkeys = NULL,
+			   *attunique = NULL;
 
 	natts = pq_getmsgint(in, 2);
 	attnames = palloc(natts * sizeof(char *));
@@ -1014,9 +1085,13 @@ logicalrep_read_attrs(StringInfo in, LogicalRepRelation *rel)
 
 		/* Check for replica identity column */
 		flags = pq_getmsgbyte(in);
-		if (flags & LOGICALREP_IS_REPLICA_IDENTITY)
+		if (flags & ATTR_IS_REPLICA_IDENTITY)
 			attkeys = bms_add_member(attkeys, i);
 
+		/* Check for unique column */
+		if (flags & ATTR_IS_UNIQUE)
+			attunique = bms_add_member(attunique, i);
+
 		/* attribute name */
 		attnames[i] = pstrdup(pq_getmsgstring(in));
 
@@ -1030,6 +1105,7 @@ logicalrep_read_attrs(StringInfo in, LogicalRepRelation *rel)
 	rel->attnames = attnames;
 	rel->atttyps = atttyps;
 	rel->attkeys = attkeys;
+	rel->attunique = attunique;
 	rel->natts = natts;
 }
 
diff --git a/src/backend/replication/logical/relation.c b/src/backend/replication/logical/relation.c
index e989047681..d761012f4f 100644
--- a/src/backend/replication/logical/relation.c
+++ b/src/backend/replication/logical/relation.c
@@ -19,12 +19,19 @@
 
 #include "access/table.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_proc.h"
 #include "catalog/pg_subscription_rel.h"
+#include "commands/trigger.h"
 #include "executor/executor.h"
 #include "nodes/makefuncs.h"
+#include "optimizer/optimizer.h"
 #include "replication/logicalrelation.h"
 #include "replication/worker_internal.h"
+#include "rewrite/rewriteHandler.h"
 #include "utils/inval.h"
+#include "utils/lsyscache.h"
+#include "utils/syscache.h"
+#include "utils/typcache.h"
 
 
 static MemoryContext LogicalRepRelMapContext = NULL;
@@ -91,6 +98,23 @@ logicalrep_relmap_invalidate_cb(Datum arg, Oid reloid)
 	}
 }
 
+/*
+ * Syscache invalidation callback to reset parallel_apply_safety flag.
+ */
+static void
+logicalrep_relmap_reset_parallel_cb(Datum arg, int cacheid, uint32 hashvalue)
+{
+	HASH_SEQ_STATUS hash_seq;
+	LogicalRepRelMapEntry *entry;
+
+	if (LogicalRepRelMap == NULL)
+		return;
+
+	hash_seq_init(&hash_seq, LogicalRepRelMap);
+	while ((entry = hash_seq_search(&hash_seq)) != NULL)
+		entry->parallel_apply_safety = PARALLEL_APPLY_SAFETY_UNKNOWN;
+}
+
 /*
  * Initialize the relation map cache.
  */
@@ -116,6 +140,12 @@ logicalrep_relmap_init(void)
 	/* Watch for invalidation events. */
 	CacheRegisterRelcacheCallback(logicalrep_relmap_invalidate_cb,
 								  (Datum) 0);
+	CacheRegisterSyscacheCallback(PROCOID,
+								  logicalrep_relmap_reset_parallel_cb,
+								  (Datum) 0);
+	CacheRegisterSyscacheCallback(TYPEOID,
+								  logicalrep_relmap_reset_parallel_cb,
+								  (Datum) 0);
 }
 
 /*
@@ -142,6 +172,7 @@ logicalrep_relmap_free_entry(LogicalRepRelMapEntry *entry)
 		pfree(remoterel->atttyps);
 	}
 	bms_free(remoterel->attkeys);
+	bms_free(remoterel->attunique);
 
 	if (entry->attrmap)
 		free_attrmap(entry->attrmap);
@@ -190,6 +221,7 @@ logicalrep_relmap_update(LogicalRepRelation *remoterel)
 	}
 	entry->remoterel.replident = remoterel->replident;
 	entry->remoterel.attkeys = bms_copy(remoterel->attkeys);
+	entry->remoterel.attunique = bms_copy(remoterel->attunique);
 	MemoryContextSwitchTo(oldctx);
 }
 
@@ -310,6 +342,162 @@ logicalrep_rel_mark_updatable(LogicalRepRelMapEntry *entry)
 	}
 }
 
+/*
+ * Check if changes on one relation can be applied using a parallel apply
+ * worker and assign the 'parallel_apply_safety' flag.
+ *
+ * There are two requirements for applying changes using a parallel apply
+ * worker: 1) the unique column in the table on the subscriber-side should also
+ * be the unique column on the publisher-side; 2) there cannot be any
+ * non-immutable functions used by the subscriber-side replicated table.
+ *
+ * Without these safety checks, the following scenario may occur: The parallel
+ * apply worker locks a row when processing a streaming transaction, after
+ * that the leader apply worker tries to lock the same row when processing
+ * another non-streamed transaction. At this time, the leader apply worker
+ * waits for the streaming transaction to complete and the lock to be released,
+ * it won't send subsequent data of the streaming transaction to the parallel
+ * apply worker; the parallel apply worker waits to receive the rest of
+ * streaming transaction and can't finish this transaction. Now a deadlock has
+ * occurred, so both workers will wait indefinitely.
+ *
+ * We just mark the relation entry as 'PARALLEL_APPLY_UNSAFE' here if changes
+ * on one relation can not be applied using a parallel apply worker and leave
+ * it to parallel_apply_relation_check() to throw the actual error if needed.
+ */
+void
+logicalrep_rel_mark_parallel_apply(LogicalRepRelMapEntry *entry)
+{
+	Bitmapset   *ukey;
+	int			i;
+	TupleDesc	tupdesc;
+	int			attnum;
+
+	/* Skip if not the parallel apply worker */
+	if (!am_parallel_apply_worker())
+		return;
+
+	/* Initialize the flag. */
+	entry->parallel_apply_safety = PARALLEL_APPLY_SAFETY_UNKNOWN;
+
+	/*
+	 * First, check if the unique column in the relation on the subscriber-side
+	 * is also the unique column on the publisher-side.
+	 */
+	ukey = RelationGetIndexAttrBitmap(entry->localrel,
+									  INDEX_ATTR_BITMAP_KEY);
+
+	if (ukey)
+	{
+		i = -1;
+		while ((i = bms_next_member(ukey, i)) >= 0)
+		{
+			attnum = AttrNumberGetAttrOffset(i + FirstLowInvalidHeapAttributeNumber);
+
+			if (entry->attrmap->attnums[attnum] < 0 ||
+				!bms_is_member(entry->attrmap->attnums[attnum], entry->remoterel.attunique))
+			{
+				entry->parallel_apply_safety = PARALLEL_APPLY_UNSAFE;
+				bms_free(ukey);
+				return;
+			}
+		}
+
+		bms_free(ukey);
+	}
+
+	/*
+	 * Then, check if there is any non-immutable function used by the
+	 * subscriber-side relation. Look for functions in the following places:
+	 * a. trigger functions;
+	 * b. Column default value expressions and domain constraints;
+	 * c. Constraint expressions;
+	 */
+	/* Check the trigger functions. */
+	if (entry->localrel->trigdesc != NULL)
+	{
+		for (i = 0; i < entry->localrel->trigdesc->numtriggers; i++)
+		{
+			Trigger    *trig = entry->localrel->trigdesc->triggers + i;
+
+			if (trig->tgenabled != TRIGGER_FIRES_ALWAYS &&
+				trig->tgenabled != TRIGGER_FIRES_ON_REPLICA)
+				continue;
+
+			if (func_volatile(trig->tgfoid) != PROVOLATILE_IMMUTABLE)
+			{
+				entry->parallel_apply_safety = PARALLEL_APPLY_UNSAFE;
+				return;
+			}
+		}
+	}
+
+	/* Check the columns. */
+	tupdesc = RelationGetDescr(entry->localrel);
+	for (attnum = 0; attnum < tupdesc->natts; attnum++)
+	{
+		Form_pg_attribute att = TupleDescAttr(tupdesc, attnum);
+		Node *defaultexpr = NULL;
+
+		/* We don't check dropped or generated attributes */
+		if (att->attisdropped || att->attgenerated)
+			continue;
+
+		defaultexpr = build_column_default(entry->localrel, attnum + 1);
+		if (defaultexpr && contain_mutable_functions(defaultexpr))
+		{
+			entry->parallel_apply_safety = PARALLEL_APPLY_UNSAFE;
+			return;
+		}
+
+		/*
+		 * If the column is of a DOMAIN type, determine whether that domain has
+		 * any CHECK expressions that are not immutable.
+		 */
+		if (get_typtype(att->atttypid) == TYPTYPE_DOMAIN)
+		{
+			List	   *domain_constraints;
+			ListCell   *lc;
+
+			domain_constraints = GetDomainConstraints(att->atttypid);
+
+			foreach(lc, domain_constraints)
+			{
+				DomainConstraintState *con = (DomainConstraintState *) lfirst(lc);
+
+				if (con->check_expr && contain_mutable_functions((Node *) con->check_expr))
+				{
+					entry->parallel_apply_safety = PARALLEL_APPLY_UNSAFE;
+					return;
+				}
+			}
+		}
+	}
+
+	/* Check the constraints. */
+	if (tupdesc->constr)
+	{
+		ConstrCheck *check = tupdesc->constr->check;
+
+		/*
+		 * Determine if there are any CHECK constraints which
+		 * contains non-immutable function.
+		 */
+		for (i = 0; i < tupdesc->constr->num_check; i++)
+		{
+			Expr	   *check_expr = stringToNode(check[i].ccbin);
+
+			if (contain_mutable_functions((Node *) check_expr))
+			{
+				entry->parallel_apply_safety = PARALLEL_APPLY_UNSAFE;
+				return;
+			}
+		}
+	}
+
+	entry->parallel_apply_safety = PARALLEL_APPLY_SAFE;
+}
+
 /*
  * Open the local relation associated with the remote one.
  *
@@ -438,6 +626,9 @@ logicalrep_rel_open(LogicalRepRelId remoteid, LOCKMODE lockmode)
 		 */
 		logicalrep_rel_mark_updatable(entry);
 
+		/* Set if changes could be applied using a parallel apply worker */
+		logicalrep_rel_mark_parallel_apply(entry);
+
 		entry->localrelvalid = true;
 	}
 
@@ -653,6 +844,7 @@ logicalrep_partition_open(LogicalRepRelMapEntry *root,
 		}
 		entry->remoterel.replident = remoterel->replident;
 		entry->remoterel.attkeys = bms_copy(remoterel->attkeys);
+		entry->remoterel.attunique = bms_copy(remoterel->attunique);
 	}
 
 	entry->localrel = partrel;
@@ -696,6 +888,9 @@ logicalrep_partition_open(LogicalRepRelMapEntry *root,
 	/* Set if the table's replica identity is enough to apply update/delete. */
 	logicalrep_rel_mark_updatable(entry);
 
+	/* Set if changes could be applied using a parallel apply worker */
+	logicalrep_rel_mark_parallel_apply(entry);
+
 	entry->localrelvalid = true;
 
 	/* state and statelsn are left set to 0. */
diff --git a/src/backend/replication/logical/tablesync.c b/src/backend/replication/logical/tablesync.c
index 47ae9a80dd..b437b74248 100644
--- a/src/backend/replication/logical/tablesync.c
+++ b/src/backend/replication/logical/tablesync.c
@@ -921,6 +921,7 @@ fetch_remote_table_info(char *nspname, char *relname,
 	lrel->attnames = palloc0(MaxTupleAttributeNumber * sizeof(char *));
 	lrel->atttyps = palloc0(MaxTupleAttributeNumber * sizeof(Oid));
 	lrel->attkeys = NULL;
+	lrel->attunique = NULL;
 
 	/*
 	 * Store the columns as a list of names.  Ignore those that are not
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 2bff1dbc74..4f811d617b 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -1505,6 +1505,14 @@ apply_handle_stream_stop(StringInfo s)
 						(errcode(ERRCODE_PROTOCOL_VIOLATION),
 						 errmsg_internal("STREAM STOP message without STREAM START")));
 
+			/*
+			 * Unlike stream_commit, we don't need to wait here for stream_stop
+			 * to finish. Allowing the other transaction to be applied before
+			 * stream_stop is finished can lead to failures if the unique
+			 * index/constraint is different between publisher and subscriber.
+			 * But for such cases, we don't allow streamed transactions to be
+			 * applied in parallel. See parallel_apply_relation_check.
+			 */
 			parallel_apply_send_data(winfo, s->len, s->data);
 
 			elog(DEBUG1, "applied %u changes in the streaming chunk", nchanges);
@@ -2103,6 +2111,8 @@ apply_handle_insert(StringInfo s)
 	/* Set relation for error callback */
 	apply_error_callback_arg.rel = rel;
 
+	parallel_apply_relation_check(rel);
+
 	/* Initialize the executor state. */
 	edata = create_edata_for_relation(rel);
 	estate = edata->estate;
@@ -2246,6 +2256,8 @@ apply_handle_update(StringInfo s)
 	/* Check if we can do the update. */
 	check_relation_updatable(rel);
 
+	parallel_apply_relation_check(rel);
+
 	/* Initialize the executor state. */
 	edata = create_edata_for_relation(rel);
 	estate = edata->estate;
@@ -2414,6 +2426,8 @@ apply_handle_delete(StringInfo s)
 	/* Check if we can do the delete. */
 	check_relation_updatable(rel);
 
+	parallel_apply_relation_check(rel);
+
 	/* Initialize the executor state. */
 	edata = create_edata_for_relation(rel);
 	estate = edata->estate;
@@ -2599,13 +2613,14 @@ apply_handle_tuple_routing(ApplyExecutionData *edata,
 	}
 	MemoryContextSwitchTo(oldctx);
 
+	part_entry = logicalrep_partition_open(relmapentry, partrel,
+										   attrmap);
+
 	/* Check if we can do the update or delete on the leaf partition. */
 	if (operation == CMD_UPDATE || operation == CMD_DELETE)
-	{
-		part_entry = logicalrep_partition_open(relmapentry, partrel,
-											   attrmap);
 		check_relation_updatable(part_entry);
-	}
+
+	parallel_apply_relation_check(part_entry);
 
 	switch (operation)
 	{
diff --git a/src/backend/utils/cache/typcache.c b/src/backend/utils/cache/typcache.c
index 808f9ebd0d..b248899d82 100644
--- a/src/backend/utils/cache/typcache.c
+++ b/src/backend/utils/cache/typcache.c
@@ -2540,6 +2540,23 @@ compare_values_of_enum(TypeCacheEntry *tcache, Oid arg1, Oid arg2)
 		return 0;
 }
 
+/*
+ * GetDomainConstraints --- get DomainConstraintState list of specified domain type
+ */
+List *
+GetDomainConstraints(Oid type_id)
+{
+	TypeCacheEntry *typentry;
+	List		   *constraints = NIL;
+
+	typentry = lookup_type_cache(type_id, TYPECACHE_DOMAIN_CONSTR_INFO);
+
+	if(typentry->domainData != NULL)
+		constraints = typentry->domainData->constraints;
+
+	return constraints;
+}
+
 /*
  * Load (or re-load) the enumData member of the typcache entry.
  */
diff --git a/src/include/replication/logicalproto.h b/src/include/replication/logicalproto.h
index 520f837473..10c6aa09b9 100644
--- a/src/include/replication/logicalproto.h
+++ b/src/include/replication/logicalproto.h
@@ -113,6 +113,7 @@ typedef struct LogicalRepRelation
 	char		replident;		/* replica identity */
 	char		relkind;		/* remote relation kind */
 	Bitmapset  *attkeys;		/* Bitmap of key columns */
+	Bitmapset  *attunique;		/* Bitmap of unique columns */
 } LogicalRepRelation;
 
 /* Type mapping info */
diff --git a/src/include/replication/logicalrelation.h b/src/include/replication/logicalrelation.h
index 78cd7e77f5..e9f5851bf5 100644
--- a/src/include/replication/logicalrelation.h
+++ b/src/include/replication/logicalrelation.h
@@ -15,6 +15,17 @@
 #include "access/attmap.h"
 #include "replication/logicalproto.h"
 
+/*
+ *	States to determine if changes on one relation can be applied using a
+ *	parallel apply worker.
+ */
+typedef enum ParallelApplySafety
+{
+	PARALLEL_APPLY_SAFETY_UNKNOWN,
+	PARALLEL_APPLY_SAFE,
+	PARALLEL_APPLY_UNSAFE
+} ParallelApplySafety;
+
 typedef struct LogicalRepRelMapEntry
 {
 	LogicalRepRelation remoterel;	/* key is remoterel.remoteid */
@@ -31,6 +42,8 @@ typedef struct LogicalRepRelMapEntry
 	Relation	localrel;		/* relcache entry (NULL when closed) */
 	AttrMap    *attrmap;		/* map of local attributes to remote ones */
 	bool		updatable;		/* Can apply updates/deletes? */
+	ParallelApplySafety	parallel_apply_safety;	/* Can apply changes in a
+												   parallel apply worker? */
 
 	/* Sync state. */
 	char		state;
@@ -47,4 +60,6 @@ extern LogicalRepRelMapEntry *logicalrep_partition_open(LogicalRepRelMapEntry *r
 extern void logicalrep_rel_close(LogicalRepRelMapEntry *rel,
 								 LOCKMODE lockmode);
 
+extern void logicalrep_rel_mark_parallel_apply(LogicalRepRelMapEntry *entry);
+
 #endif							/* LOGICALRELATION_H */
diff --git a/src/include/replication/worker_internal.h b/src/include/replication/worker_internal.h
index aca3de72b7..c74670dd35 100644
--- a/src/include/replication/worker_internal.h
+++ b/src/include/replication/worker_internal.h
@@ -223,6 +223,8 @@ extern void parallel_apply_replorigin_reset(void);
 
 #define isParallelApplyWorker(worker) (worker->apply_leader_pid != InvalidPid)
 
+extern void parallel_apply_relation_check(LogicalRepRelMapEntry *rel);
+
 static inline bool
 am_tablesync_worker(void)
 {
diff --git a/src/include/utils/typcache.h b/src/include/utils/typcache.h
index 431ad7f1b3..ed7c2e7f48 100644
--- a/src/include/utils/typcache.h
+++ b/src/include/utils/typcache.h
@@ -199,6 +199,8 @@ extern uint64 assign_record_type_identifier(Oid type_id, int32 typmod);
 
 extern int	compare_values_of_enum(TypeCacheEntry *tcache, Oid arg1, Oid arg2);
 
+extern List *GetDomainConstraints(Oid type_id);
+
 extern size_t SharedRecordTypmodRegistryEstimate(void);
 
 extern void SharedRecordTypmodRegistryInit(SharedRecordTypmodRegistry *,
diff --git a/src/test/subscription/t/015_stream.pl b/src/test/subscription/t/015_stream.pl
index f0e12190ce..549f55b80c 100644
--- a/src/test/subscription/t/015_stream.pl
+++ b/src/test/subscription/t/015_stream.pl
@@ -204,8 +204,13 @@ my $oldpid = $node_publisher->safe_psql('postgres',
 	"SELECT pid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
 );
 
-$node_subscriber->safe_psql('postgres',
-	"ALTER SUBSCRIPTION tap_sub SET(streaming = parallel, binary = off)");
+# "streaming = parallel" does not support non-immutable functions, so change
+# the function in the default expression of column "c".
+$node_subscriber->safe_psql(
+	'postgres', qq{
+ALTER TABLE test_tab ALTER COLUMN c SET DEFAULT to_timestamp(0);
+ALTER SUBSCRIPTION tap_sub SET(streaming = parallel, binary = off);
+});
 
 $node_publisher->poll_query_until('postgres',
 	"SELECT pid != $oldpid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
diff --git a/src/test/subscription/t/016_stream_subxact.pl b/src/test/subscription/t/016_stream_subxact.pl
index 9d7e8506c4..b5156d9750 100644
--- a/src/test/subscription/t/016_stream_subxact.pl
+++ b/src/test/subscription/t/016_stream_subxact.pl
@@ -149,8 +149,13 @@ my $oldpid = $node_publisher->safe_psql('postgres',
 	"SELECT pid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
 );
 
-$node_subscriber->safe_psql('postgres',
-	"ALTER SUBSCRIPTION tap_sub SET(streaming = parallel)");
+# "streaming = parallel" does not support non-immutable functions, so change
+# the function in the default expression of column "c".
+$node_subscriber->safe_psql(
+	'postgres', qq{
+ALTER TABLE test_tab ALTER COLUMN c SET DEFAULT to_timestamp(0);
+ALTER SUBSCRIPTION tap_sub SET(streaming = parallel);
+});
 
 $node_publisher->poll_query_until('postgres',
 	"SELECT pid != $oldpid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
diff --git a/src/test/subscription/t/022_twophase_cascade.pl b/src/test/subscription/t/022_twophase_cascade.pl
index 3b5830a3b4..8c704969ce 100644
--- a/src/test/subscription/t/022_twophase_cascade.pl
+++ b/src/test/subscription/t/022_twophase_cascade.pl
@@ -500,6 +500,14 @@ test_streaming($node_A, $node_B, $node_C, $appname_B, $appname_C, 'on');
 ######################################
 # Test using streaming mode 'parallel'
 ######################################
+
+# "streaming = parallel" does not support non-immutable functions, so change
+# the function in the default expression of column "c".
+$node_B->safe_psql(
+	'postgres', "ALTER TABLE test_tab ALTER COLUMN c SET DEFAULT to_timestamp(0);");
+$node_C->safe_psql(
+	'postgres', "ALTER TABLE test_tab ALTER COLUMN c SET DEFAULT to_timestamp(0);");
+
 test_streaming($node_A, $node_B, $node_C, $appname_B, $appname_C, 'parallel');
 
 ###############################
diff --git a/src/test/subscription/t/023_twophase_stream.pl b/src/test/subscription/t/023_twophase_stream.pl
index 29989156f8..fc96999706 100644
--- a/src/test/subscription/t/023_twophase_stream.pl
+++ b/src/test/subscription/t/023_twophase_stream.pl
@@ -383,8 +383,13 @@ my $oldpid = $node_publisher->safe_psql('postgres',
 	"SELECT pid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
 );
 
-$node_subscriber->safe_psql('postgres',
-	"ALTER SUBSCRIPTION tap_sub SET(streaming = parallel)");
+# "streaming = parallel" does not support non-immutable functions, so change
+# the function in the default expression of column "c".
+$node_subscriber->safe_psql(
+	'postgres', qq{
+ALTER TABLE test_tab ALTER COLUMN c SET DEFAULT to_timestamp(0);
+ALTER SUBSCRIPTION tap_sub SET(streaming = parallel);
+});
 
 $node_publisher->poll_query_until('postgres',
 	"SELECT pid != $oldpid FROM pg_stat_replication WHERE application_name = '$appname' AND state = 'streaming';"
diff --git a/src/test/subscription/t/032_streaming_parallel_safety.pl b/src/test/subscription/t/032_streaming_parallel_safety.pl
new file mode 100644
index 0000000000..6fdbea36c6
--- /dev/null
+++ b/src/test/subscription/t/032_streaming_parallel_safety.pl
@@ -0,0 +1,609 @@
+# Copyright (c) 2022, PostgreSQL Global Development Group
+
+# Test the safety checks of streaming mode "parallel" in logical replication.
+# Without these safety checks, the subscriber's apply worker may fall into an
+# infinite wait without the user knowing.
+#
+# For normal tables, we use deadlock-producing test cases to ensure that future
+# modifications do not invalidate constraint checks.
+#
+# For partitioned tables, we just use test cases to confirm that the constraint
+# checks are as expected.
+
+use strict;
+use warnings;
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+my $offset = 0;
+
+# Create publisher node
+my $node_publisher = PostgreSQL::Test::Cluster->new('publisher');
+$node_publisher->init(allows_streaming => 'logical');
+$node_publisher->append_conf('postgresql.conf',
+	'logical_decoding_work_mem = 64kB');
+$node_publisher->start;
+
+# Create subscriber node
+my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
+$node_subscriber->init;
+$node_subscriber->start;
+
+# Setup structure on publisher
+$node_publisher->safe_psql('postgres',
+	"CREATE TABLE test_tab1 (a int)");
+$node_publisher->safe_psql('postgres',
+	"CREATE TABLE test_tab2 (a int)");
+$node_publisher->safe_psql('postgres',
+	"CREATE TABLE test_tab_partitioned (a int primary key, b varchar)");
+
+# Setup structure on subscriber
+# We need to test normal table and partition table.
+$node_subscriber->safe_psql('postgres',
+	"CREATE TABLE test_tab1 (a int)");
+$node_subscriber->safe_psql('postgres',
+	"CREATE TABLE test_tab2 (a int)");
+$node_subscriber->safe_psql('postgres',
+	"CREATE TABLE test_tab_partitioned (a int primary key, b varchar) PARTITION BY RANGE(a)");
+$node_subscriber->safe_psql('postgres',
+	"CREATE TABLE test_tab_partition (LIKE test_tab_partitioned)");
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE test_tab_partitioned ATTACH PARTITION test_tab_partition DEFAULT"
+);
+
+# Setup logical replication
+my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
+$node_publisher->safe_psql('postgres',
+	"CREATE PUBLICATION tap_pub_normal FOR TABLE test_tab1, test_tab2");
+$node_publisher->safe_psql('postgres',
+	"CREATE PUBLICATION tap_pub_partitioned FOR TABLE test_tab_partitioned");
+
+my $appname = 'tap_sub';
+$node_subscriber->safe_psql(
+	'postgres', "
+	CREATE SUBSCRIPTION tap_sub
+	CONNECTION '$publisher_connstr application_name=$appname'
+	PUBLICATION tap_pub_normal, tap_pub_partitioned
+	WITH (streaming = parallel, copy_data = false)");
+
+$node_publisher->wait_for_catchup($appname);
+
+# Interleave a pair of transactions, each exceeding the 64kB limit.
+my $in  = '';
+my $out = '';
+
+my $timer = IPC::Run::timeout($PostgreSQL::Test::Utils::timeout_default);
+
+my $h = $node_publisher->background_psql('postgres', \$in, \$out, $timer,
+	on_error_stop => 0);
+
+# ============================================================================
+# It is not allowed that the unique column in the relation on the
+# subscriber-side is not the unique column on the publisher-side. Check the
+# error reported by parallel worker in this case.
+# ============================================================================
+
+# First we check the unique index on normal table.
+$node_subscriber->safe_psql('postgres',
+	"CREATE UNIQUE INDEX idx_tab1 on test_tab1(a)");
+
+$in .= q{
+BEGIN;
+INSERT INTO test_tab1 SELECT i FROM generate_series(1, 5000) s(i);
+};
+$h->pump_nb;
+
+$node_publisher->safe_psql('postgres', "INSERT INTO test_tab1 values(1)");
+
+$in .= q{
+COMMIT;
+\q
+};
+$h->finish;
+
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
+	$offset);
+
+# Drop the unique index on the subscriber, now it works.
+$node_subscriber->safe_psql('postgres', "DROP INDEX idx_tab1");
+
+# Wait for this streaming transaction to be applied in the apply worker.
+$node_publisher->wait_for_catchup($appname);
+
+my $result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
+is($result, qq(5001), 'data replicated to subscriber after dropping index');
+
+# Clean up test data from the environment.
+$node_publisher->safe_psql('postgres', "TRUNCATE TABLE test_tab1");
+$node_publisher->wait_for_catchup($appname);
+
+# Then we check the unique index on partition table.
+$node_subscriber->safe_psql('postgres',
+	"CREATE UNIQUE INDEX test_tab_b_partition_idx ON test_tab_partition (b)");
+
+# Check the subscriber log from now on.
+$offset = -s $node_subscriber->logfile;
+
+$node_publisher->safe_psql('postgres',
+	"INSERT INTO test_tab_partitioned SELECT i, md5(i::text) FROM generate_series(1, 5000) s(i)"
+);
+
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab_partitioned" using subscription parameter streaming = parallel/,
+	$offset);
+
+# Drop the unique index on the subscriber, now it works.
+$node_subscriber->safe_psql('postgres', "DROP INDEX test_tab_b_partition_idx");
+
+# Wait for this streaming transaction to be applied in the apply worker.
+$node_publisher->wait_for_catchup($appname);
+
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab_partitioned");
+is($result, qq(5000), 'data replicated to subscriber after dropping index');
+
+# ============================================================================
+# Triggers which execute non-immutable function are not allowed on the
+# subscriber side. Check the error reported by parallel worker in this case.
+# ============================================================================
+
+# First we check the trigger function on normal table.
+$node_publisher->safe_psql('postgres',
+	"CREATE UNIQUE INDEX idx_tab2 on test_tab2(a)");
+$node_subscriber->safe_psql('postgres',
+	"CREATE UNIQUE INDEX idx_tab2 on test_tab2(a)");
+
+$node_subscriber->safe_psql(
+	'postgres', qq{
+CREATE FUNCTION trigger_func_tab1_unsafe() RETURNS TRIGGER AS \$\$
+  BEGIN
+    INSERT INTO public.test_tab2 VALUES (NEW.*);
+    RETURN NEW;
+  END
+\$\$ language plpgsql;
+CREATE TRIGGER tri_tab1_unsafe
+BEFORE INSERT ON public.test_tab1
+FOR EACH ROW EXECUTE PROCEDURE trigger_func_tab1_unsafe();
+ALTER TABLE test_tab1 ENABLE REPLICA TRIGGER tri_tab1_unsafe;
+
+CREATE FUNCTION trigger_func_tab1_safe() RETURNS TRIGGER AS \$\$
+  BEGIN
+    RAISE NOTICE 'test for safe trigger function';
+	RETURN NEW;
+  END
+\$\$ language plpgsql;
+ALTER FUNCTION trigger_func_tab1_safe IMMUTABLE;
+CREATE TRIGGER tri_tab1_safe
+BEFORE INSERT ON public.test_tab1
+FOR EACH ROW EXECUTE PROCEDURE trigger_func_tab1_safe();
+});
+
+# Check the subscriber log from now on.
+$offset = -s $node_subscriber->logfile;
+
+$in .= q{
+BEGIN;
+INSERT INTO test_tab1 VALUES(5001);
+INSERT INTO test_tab2 SELECT i FROM generate_series(1, 5000) s(i);
+};
+$h->pump_nb;
+
+$node_publisher->safe_psql('postgres', "INSERT INTO test_tab1 VALUES(5001)");
+
+$in .= q{
+COMMIT;
+\q
+};
+$h->finish;
+
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
+	$offset);
+
+# Using trigger with immutable function, now it works.
+$node_subscriber->safe_psql(
+	'postgres', qq{
+ALTER TABLE test_tab1 ENABLE REPLICA TRIGGER tri_tab1_safe;
+DROP TRIGGER tri_tab1_unsafe ON public.test_tab1;
+});
+
+# Wait for this streaming transaction to be applied in the apply worker.
+$node_publisher->wait_for_catchup($appname);
+
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
+is($result, qq(2), 'data replicated to subscriber after using immutable expression');
+
+# Clean up test data from the environment.
+$node_subscriber->safe_psql(
+	'postgres', qq{
+DROP INDEX idx_tab2;
+DROP TRIGGER tri_tab1_safe ON public.test_tab1;
+DROP function trigger_func_tab1_unsafe;
+DROP function trigger_func_tab1_safe;
+});
+$node_publisher->safe_psql(
+	'postgres', qq{
+DROP INDEX idx_tab2;
+TRUNCATE TABLE test_tab1;
+TRUNCATE TABLE test_tab2;
+});
+$node_publisher->wait_for_catchup($appname);
+
+# Then we check the trigger function on partition table.
+$node_subscriber->safe_psql(
+	'postgres', qq{
+CREATE FUNCTION trigger_func() RETURNS TRIGGER AS \$\$
+  BEGIN
+    RETURN NULL;
+  END
+\$\$ language plpgsql;
+CREATE TRIGGER insert_trig
+BEFORE INSERT ON test_tab_partition
+FOR EACH ROW EXECUTE PROCEDURE trigger_func();
+ALTER TABLE test_tab_partition ENABLE REPLICA TRIGGER insert_trig;
+});
+
+# Check the subscriber log from now on.
+$offset = -s $node_subscriber->logfile;
+
+$node_publisher->safe_psql('postgres', "DELETE FROM test_tab_partitioned");
+
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab_partitioned" using subscription parameter streaming = parallel/,
+	$offset);
+
+# Drop the trigger on the subscriber, now it works.
+$node_subscriber->safe_psql('postgres',
+	"DROP TRIGGER insert_trig ON test_tab_partition");
+
+# Wait for this streaming transaction to be applied in the apply worker.
+$node_publisher->wait_for_catchup($appname);
+
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab_partitioned");
+is($result, qq(0), 'data replicated to subscriber after dropping trigger');
+
+# ============================================================================
+# It is not allowed that column default value expression contains a
+# non-immutable function on the subscriber side. Check the error reported by
+# parallel worker in this case.
+# ============================================================================
+
+# First we check the column default value expression on normal table.
+$node_publisher->safe_psql('postgres', "INSERT INTO test_tab2 VALUES(1)");
+
+$node_subscriber->safe_psql(
+	'postgres', qq{
+CREATE FUNCTION func_count_tab2() RETURNS INT AS \$\$
+  BEGIN
+    RETURN (SELECT count(*) FROM public.test_tab2);
+  END
+\$\$ language plpgsql;
+ALTER TABLE test_tab1 ADD COLUMN b int DEFAULT func_count_tab2();
+});
+
+# Check the subscriber log from now on.
+$offset = -s $node_subscriber->logfile;
+
+$in .= q{
+BEGIN;
+TRUNCATE test_tab2;
+INSERT INTO test_tab1 SELECT i FROM generate_series(1, 5000) s(i);
+};
+$h->pump_nb;
+
+$node_publisher->safe_psql('postgres', "INSERT INTO test_tab1(a) VALUES(1)");
+
+$in .= q{
+COMMIT;
+\q
+};
+$h->finish;
+
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
+	$offset);
+
+# Alter default values to immutable expression, now it works.
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE test_tab1 ALTER COLUMN b SET DEFAULT 1");
+
+# Wait for this streaming transaction to be applied in the apply worker.
+$node_publisher->wait_for_catchup($appname);
+
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
+is($result, qq(5001),
+	'data replicated to subscriber after using immutable expression');
+
+# Clean up test data from the environment.
+$node_subscriber->safe_psql('postgres', "ALTER TABLE test_tab1 DROP COLUMN b");
+$node_publisher->safe_psql(
+	'postgres', qq{
+TRUNCATE TABLE test_tab1;
+TRUNCATE TABLE test_tab2;
+});
+$node_publisher->wait_for_catchup($appname);
+
+# Then we check the column default value expression on partition table.
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE test_tab_partition ALTER COLUMN b SET DEFAULT random()");
+
+# Check the subscriber log from now on.
+$offset = -s $node_subscriber->logfile;
+
+$node_publisher->safe_psql('postgres',
+	"INSERT INTO test_tab_partitioned SELECT i, md5(i::text) FROM generate_series(1, 5000) s(i)"
+);
+
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab_partitioned" using subscription parameter streaming = parallel/,
+	$offset);
+
+# Drop default value on the subscriber, now it works.
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE test_tab_partition ALTER COLUMN b DROP DEFAULT");
+
+# Wait for this streaming transaction to be applied in the apply worker.
+$node_publisher->wait_for_catchup($appname);
+
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab_partitioned");
+is($result, qq(5000),
+	'data replicated to subscriber after dropping default value expression');
+
+# ============================================================================
+# It is not allowed that domain constraint expression contains a non-immutable
+# function on the subscriber side. Check the error reported by parallel
+# worker in this case.
+# ============================================================================
+
+# Because the column type of the partition table must be the same as its parent
+# table, only test normal table here.
+$node_publisher->safe_psql('postgres', "INSERT INTO test_tab2 VALUES(1)");
+
+$node_publisher->safe_psql(
+	'postgres', qq{
+CREATE DOMAIN tmp_domain AS int CHECK (VALUE > -1);
+ALTER TABLE test_tab1 ALTER COLUMN a TYPE tmp_domain;
+});
+
+$node_subscriber->safe_psql(
+	'postgres', qq{
+CREATE DOMAIN tmp_domain AS INT CONSTRAINT domain_check CHECK (VALUE >= func_count_tab2());
+ALTER TABLE test_tab1 ALTER COLUMN a TYPE tmp_domain;
+});
+
+# Check the subscriber log from now on.
+$offset = -s $node_subscriber->logfile;
+
+$in .= q{
+BEGIN;
+TRUNCATE test_tab2;
+INSERT INTO test_tab1 SELECT i FROM generate_series(1, 5000) s(i);
+};
+$h->pump_nb;
+
+$node_publisher->safe_psql('postgres', "INSERT INTO test_tab1(a) VALUES(1)");
+
+$in .= q{
+COMMIT;
+\q
+};
+$h->finish;
+
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
+	$offset);
+
+# Drop domain constraint expression, now it works.
+$node_subscriber->safe_psql('postgres',
+	"ALTER DOMAIN tmp_domain DROP CONSTRAINT domain_check");
+
+# Wait for this streaming transaction to be applied in the apply worker.
+$node_publisher->wait_for_catchup($appname);
+
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
+is($result, qq(5001),
+	'data replicated to subscriber after using immutable expression'
+);
+
+# Clean up test data from the environment.
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE test_tab1 ALTER COLUMN a TYPE int");
+$node_publisher->safe_psql(
+	'postgres', qq{
+TRUNCATE TABLE test_tab1;
+TRUNCATE TABLE test_tab2;
+});
+$node_publisher->wait_for_catchup($appname);
+
+# ============================================================================
+# It is not allowed that constraint expression contains a non-immutable function
+# on the subscriber side. Check the error reported by parallel worker in this
+# case.
+# ============================================================================
+
+# First we check the constraint expression on normal table.
+$node_publisher->safe_psql('postgres', "INSERT INTO test_tab2 VALUES(1)");
+
+$node_subscriber->safe_psql(
+	'postgres', qq{
+ALTER TABLE test_tab1 ADD CONSTRAINT const_tab1_unsafe CHECK(a >= func_count_tab2());
+});
+
+# Check the subscriber log from now on.
+$offset = -s $node_subscriber->logfile;
+
+$in .= q{
+BEGIN;
+TRUNCATE test_tab2;
+INSERT INTO test_tab1 SELECT i FROM generate_series(1, 5000) s(i);
+};
+$h->pump_nb;
+
+$node_publisher->safe_psql('postgres', "INSERT INTO test_tab1(a) VALUES(1)");
+
+$in .= q{
+COMMIT;
+\q
+};
+$h->finish;
+
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
+	$offset);
+
+# Alter constraint expression to immutable expression, now it works.
+$node_subscriber->safe_psql(
+	'postgres', qq{
+ALTER TABLE test_tab1 DROP CONSTRAINT const_tab1_unsafe;
+ALTER TABLE test_tab1 ADD CONSTRAINT const_tab1_safe CHECK(a >= 0);
+});
+
+# Wait for this streaming transaction to be applied in the apply worker.
+$node_publisher->wait_for_catchup($appname);
+
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
+is($result, qq(5001),
+	'data replicated to subscriber after using immutable expression');
+
+# Clean up test data from the environment.
+$node_subscriber->safe_psql('postgres', "ALTER TABLE test_tab1 DROP CONSTRAINT const_tab1_safe");
+$node_publisher->safe_psql(
+	'postgres', qq{
+TRUNCATE TABLE test_tab1;
+TRUNCATE TABLE test_tab2;
+});
+$node_publisher->wait_for_catchup($appname);
+
+# Then we check the constraint expression on partition table.
+$node_subscriber->safe_psql(
+	'postgres', qq{
+ALTER TABLE test_tab_partition ADD CONSTRAINT test_tab_con check (a > random());
+});
+
+# Check the subscriber log from now on.
+$offset = -s $node_subscriber->logfile;
+
+$node_publisher->safe_psql('postgres', "DELETE FROM test_tab_partitioned");
+
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab_partitioned" using subscription parameter streaming = parallel/,
+	$offset);
+
+# Drop constraint on the subscriber, now it works.
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE test_tab_partition DROP CONSTRAINT test_tab_con");
+
+# Wait for this streaming transaction to be applied in the apply worker.
+$node_publisher->wait_for_catchup($appname);
+
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab_partitioned");
+is($result, qq(0),
+	'data replicated to subscriber after dropping constraint expression');
+
+# ============================================================================
+# It is not allowed that foreign key on the subscriber side. Check the error
+# reported by parallel worker in this case.
+# ============================================================================
+
+# First we check the foreign key on normal table.
+$node_publisher->safe_psql(
+	'postgres', qq{
+CREATE TABLE tab_nopublic(a int);
+ALTER TABLE test_tab2 ADD PRIMARY KEY (a);
+ALTER TABLE test_tab2 REPLICA IDENTITY FULL;
+INSERT INTO test_tab2 VALUES(1);
+});
+$node_subscriber->safe_psql('postgres', "ALTER TABLE test_tab2 ADD PRIMARY KEY (a);");
+
+$node_subscriber->safe_psql(
+	'postgres', qq{
+ALTER TABLE test_tab1 ADD CONSTRAINT test_tab1fk FOREIGN KEY(a) REFERENCES test_tab2(a);
+SELECT 'ALTER TABLE test_tab1 ENABLE REPLICA TRIGGER "' || tgname || '"' FROM pg_trigger WHERE tgrelid = 'test_tab1'::regclass::oid \\gexec
+});
+
+# Check the subscriber log from now on.
+$offset = -s $node_subscriber->logfile;
+
+$in .= q{
+BEGIN;
+INSERT INTO test_tab1(a) VALUES(1);
+INSERT INTO tab_nopublic SELECT i FROM generate_series(1, 5000) s(i);
+};
+$h->pump_nb;
+
+$node_publisher->safe_psql('postgres', "DELETE FROM test_tab2");
+
+$in .= q{
+COMMIT;
+\q
+};
+$h->finish;
+
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
+	$offset);
+
+# Drop the foreign key constraint on the subscriber, now it works.
+$node_subscriber->safe_psql('postgres', "ALTER TABLE test_tab1 DROP CONSTRAINT test_tab1fk");
+
+# Wait for this streaming transaction to be applied in the apply worker.
+$node_publisher->wait_for_catchup($appname);
+
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
+is($result, qq(1),
+	'data replicated to subscriber after dropping the foreign key');
+
+# Clean up test data from the environment.
+$node_publisher->safe_psql(
+	'postgres', qq{
+TRUNCATE TABLE test_tab1;
+TRUNCATE TABLE test_tab2;
+});
+$node_publisher->wait_for_catchup($appname);
+
+# Then we check the foreign key on partition table.
+$node_subscriber->safe_psql(
+	'postgres', qq{
+CREATE TABLE test_tab_partition_f (a int primary key);
+ALTER TABLE test_tab_partition ADD CONSTRAINT test_tab_patition_fk FOREIGN KEY(a) REFERENCES test_tab_partition_f(a);
+SELECT 'ALTER TABLE test_tab_partition ENABLE REPLICA TRIGGER "' || tgname || '"' FROM pg_trigger WHERE tgrelid = 'test_tab_partition'::regclass::oid \\gexec
+});
+
+# Check the subscriber log from now on.
+$offset = -s $node_subscriber->logfile;
+
+$node_publisher->safe_psql('postgres',
+	"INSERT INTO test_tab_partitioned SELECT i, md5(i::text) FROM generate_series(1, 5000) s(i)"
+);
+
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab_partitioned" using subscription parameter streaming = parallel/,
+	$offset);
+
+# Drop the foreign key constraint on the subscriber, now it works.
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE test_tab_partition DROP CONSTRAINT test_tab_patition_fk");
+
+# Wait for this streaming transaction to be applied in the apply worker.
+$node_publisher->wait_for_catchup($appname);
+
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab_partitioned");
+is($result, qq(5000),
+	'data replicated to subscriber after dropping the foreign key');
+
+$node_subscriber->stop;
+$node_publisher->stop;
+
+done_testing();
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index d205aed082..8b2532e7d6 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1878,6 +1878,7 @@ PageXLogRecPtr
 PagetableEntry
 Pairs
 ParallelAppendState
+ParallelApplySafety
 ParallelBitmapHeapState
 ParallelBlockTableScanDesc
 ParallelBlockTableScanWorker
-- 
2.23.0.windows.1



  [application/octet-stream] v29-0004-Retry-to-apply-streaming-xact-only-in-apply-work.patch (60.1K, ../OS3PR01MB6275F145878B4A44586C46CE9E499@OS3PR01MB6275.jpnprd01.prod.outlook.com/5-v29-0004-Retry-to-apply-streaming-xact-only-in-apply-work.patch)
  download | inline diff:
From db7edcb6a5c6e73e9be2e8144675d3f1c7c52f4c Mon Sep 17 00:00:00 2001
From: "houzj.fnst" <[email protected]>
Date: Wed, 24 Aug 2022 21:07:44 +0800
Subject: [PATCH v29 4/5] Retry to apply streaming xact only in apply worker

When the subscription parameter is set streaming=parallel, the logic tries to
apply the streaming transaction using a parallel apply worker. If this
fails the parallel worker exits with an error.

In this case, retry applying the streaming transaction using the normal
streaming=on mode. This is done to avoid getting caught in a loop of the same
retry errors.

A new flag field "subretry" has been introduced to catalog "pg_subscription".
If the subscriber exits with an error, this flag will be set true, and
whenever the transaction is applied successfully, this flag is reset false.
Now, when deciding how to apply a streaming transaction, the logic can know if
this transaction has previously failed or not (by checking the "subretry"
field).

In addition, when introduced parallel apply worker, we added some log checks to
ensure that streamed transactions are applied in parallel apply worker.
But since we introduced "retry" now, we will not be able to confirm whether
streamed transactions will be applied in parallel apply worker. So removed
these log checks.
---
 doc/src/sgml/catalogs.sgml                    |   9 +
 doc/src/sgml/ref/create_subscription.sgml     |   5 +
 src/backend/catalog/pg_subscription.c         |   1 +
 src/backend/catalog/system_views.sql          |   2 +-
 src/backend/commands/subscriptioncmds.c       |   1 +
 .../replication/logical/applyparallelworker.c |  16 +-
 src/backend/replication/logical/worker.c      | 187 +++++++++++++-----
 src/bin/pg_dump/pg_dump.c                     |   5 +-
 src/include/catalog/pg_subscription.h         |   4 +
 src/test/subscription/t/015_stream.pl         |  55 +-----
 src/test/subscription/t/016_stream_subxact.pl |  44 +----
 src/test/subscription/t/017_stream_ddl.pl     |  50 +----
 .../t/018_stream_subxact_abort.pl             |  55 +-----
 .../t/019_stream_subxact_ddl_abort.pl         |  45 +----
 .../subscription/t/022_twophase_cascade.pl    |  53 -----
 .../subscription/t/023_twophase_stream.pl     |  65 +-----
 .../t/032_streaming_parallel_safety.pl        | 140 ++++++-------
 17 files changed, 260 insertions(+), 477 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index c5769da26b..792749c560 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -7927,6 +7927,15 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>subretry</structfield> <type>bool</type>
+      </para>
+      <para>
+       True if the previous apply change failed, necessitating a retry
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>subconninfo</structfield> <type>text</type>
diff --git a/doc/src/sgml/ref/create_subscription.sgml b/doc/src/sgml/ref/create_subscription.sgml
index ef256346b8..f74250eb57 100644
--- a/doc/src/sgml/ref/create_subscription.sgml
+++ b/doc/src/sgml/ref/create_subscription.sgml
@@ -250,6 +250,11 @@ CREATE SUBSCRIPTION <replaceable class="parameter">subscription_name</replaceabl
           also be the unique column on the publisher-side; 2) there cannot be
           any non-immutable functions used by the subscriber-side replicated
           table.
+          When applying a streaming transaction, if either requirement is not
+          met, the parallel apply worker will exit with an error.
+          The <literal>parallel</literal> mode is disregarded when retrying;
+          instead the transaction will be applied using <literal>on</literal>
+          mode.
          </para>
         </listitem>
        </varlistentry>
diff --git a/src/backend/catalog/pg_subscription.c b/src/backend/catalog/pg_subscription.c
index a506fc3ec8..723b141c74 100644
--- a/src/backend/catalog/pg_subscription.c
+++ b/src/backend/catalog/pg_subscription.c
@@ -71,6 +71,7 @@ GetSubscription(Oid subid, bool missing_ok)
 	sub->stream = subform->substream;
 	sub->twophasestate = subform->subtwophasestate;
 	sub->disableonerr = subform->subdisableonerr;
+	sub->retry = subform->subretry;
 
 	/* Get conninfo */
 	datum = SysCacheGetAttr(SUBSCRIPTIONOID,
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 55f7ec79e0..f4a00496ee 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1298,7 +1298,7 @@ REVOKE ALL ON pg_replication_origin_status FROM public;
 REVOKE ALL ON pg_subscription FROM public;
 GRANT SELECT (oid, subdbid, subskiplsn, subname, subowner, subenabled,
               subbinary, substream, subtwophasestate, subdisableonerr,
-              subslotname, subsynccommit, subpublications, suborigin)
+              subretry, subslotname, subsynccommit, subpublications, suborigin)
     ON pg_subscription TO public;
 
 CREATE VIEW pg_stat_subscription_stats AS
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index fa5a0cc405..c4f39004b5 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -637,6 +637,7 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 					 LOGICALREP_TWOPHASE_STATE_PENDING :
 					 LOGICALREP_TWOPHASE_STATE_DISABLED);
 	values[Anum_pg_subscription_subdisableonerr - 1] = BoolGetDatum(opts.disableonerr);
+	values[Anum_pg_subscription_subretry - 1] = BoolGetDatum(false);
 	values[Anum_pg_subscription_subconninfo - 1] =
 		CStringGetTextDatum(conninfo);
 	if (opts.slot_name)
diff --git a/src/backend/replication/logical/applyparallelworker.c b/src/backend/replication/logical/applyparallelworker.c
index d64ae5fb26..6a1d938e35 100644
--- a/src/backend/replication/logical/applyparallelworker.c
+++ b/src/backend/replication/logical/applyparallelworker.c
@@ -144,6 +144,18 @@ parallel_apply_can_start(TransactionId xid)
 	if (!XLogRecPtrIsInvalid(MySubscription->skiplsn))
 		return false;
 
+	/*
+	 * Don't use parallel apply workers for retries, because it is possible
+	 * that the last time we tried to apply a transaction using a parallel
+	 * apply worker the checks failed (see function
+	 * parallel_apply_relation_check).
+	 */
+	if (MySubscription->retry)
+	{
+		elog(DEBUG1, "parallel apply workers are not used for retries");
+		return false;
+	}
+
 	/*
 	 * For streaming transactions that are being applied using a parallel apply
 	 * worker, we cannot decide whether to apply the change for a relation that
@@ -1114,7 +1126,5 @@ parallel_apply_relation_check(LogicalRepRelMapEntry *rel)
 						"streaming = parallel"),
 				 errdetail("The unique column on subscriber is not the unique "
 						   "column on publisher or there is at least one "
-						   "non-immutable function."),
-				 errhint("Please change to use subscription parameter %s.",
-						"streaming = on")));
+						   "non-immutable function.")));
 }
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index 4f811d617b..045b77e771 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -395,7 +395,7 @@ static void store_flush_position(XLogRecPtr remote_lsn);
 
 static void maybe_reread_subscription(void);
 
-static void DisableSubscriptionAndExit(void);
+static void DisableSubscriptionOnError(void);
 
 static void apply_handle_commit_internal(LogicalRepCommitData *commit_data);
 static void apply_handle_insert_internal(ApplyExecutionData *edata,
@@ -435,6 +435,8 @@ static inline void reset_apply_error_context_info(void);
 static TransApplyAction get_transaction_apply_action(TransactionId xid,
 													 ParallelApplyWorkerInfo **winfo);
 
+static void set_subscription_retry(bool retry);
+
 /*
  * Should this worker apply changes for given relation.
  *
@@ -982,6 +984,9 @@ apply_handle_commit(StringInfo s)
 
 	apply_handle_commit_internal(&commit_data);
 
+	/* Reset the retry flag. */
+	set_subscription_retry(false);
+
 	/* Process any tables that are being synchronized in parallel. */
 	process_syncing_tables(commit_data.end_lsn);
 
@@ -1091,6 +1096,9 @@ apply_handle_prepare(StringInfo s)
 
 	in_remote_transaction = false;
 
+	/* Reset the retry flag. */
+	set_subscription_retry(false);
+
 	/* Process any tables that are being synchronized in parallel. */
 	process_syncing_tables(prepare_data.end_lsn);
 
@@ -1147,6 +1155,9 @@ apply_handle_commit_prepared(StringInfo s)
 	store_flush_position(prepare_data.end_lsn);
 	in_remote_transaction = false;
 
+	/* Reset the retry flag. */
+	set_subscription_retry(false);
+
 	/* Process any tables that are being synchronized in parallel. */
 	process_syncing_tables(prepare_data.end_lsn);
 
@@ -1208,6 +1219,9 @@ apply_handle_rollback_prepared(StringInfo s)
 	store_flush_position(rollback_data.rollback_end_lsn);
 	in_remote_transaction = false;
 
+	/* Reset the retry flag. */
+	set_subscription_retry(false);
+
 	/* Process any tables that are being synchronized in parallel. */
 	process_syncing_tables(rollback_data.rollback_end_lsn);
 
@@ -1259,6 +1273,9 @@ apply_handle_stream_prepare(StringInfo s)
 
 			/* Unlink the files with serialized changes and subxact info. */
 			stream_cleanup_files(MyLogicalRepWorker->subid, prepare_data.xid);
+
+			/* Reset the retry flag. */
+			set_subscription_retry(false);
 			break;
 
 		case TRANS_LEADER_SEND_TO_PARALLEL:
@@ -1280,6 +1297,9 @@ apply_handle_stream_prepare(StringInfo s)
 			parallel_apply_free_worker(winfo, prepare_data.xid);
 
 			store_flush_position(prepare_data.end_lsn);
+
+			/* Reset the retry flag. */
+			set_subscription_retry(false);
 			break;
 
 		case TRANS_PARALLEL_APPLY:
@@ -1663,6 +1683,10 @@ apply_handle_stream_abort(StringInfo s)
 			 * serialized to file.
 			 */
 			serialize_stream_abort(xid, subxid);
+
+			/* Reset the retry flag. */
+			if (subxid == xid)
+				set_subscription_retry(false);
 			break;
 
 		case TRANS_LEADER_SEND_TO_PARALLEL:
@@ -1685,6 +1709,9 @@ apply_handle_stream_abort(StringInfo s)
 			{
 				parallel_apply_replorigin_setup();
 				parallel_apply_free_worker(winfo, xid);
+
+				/* Reset the retry flag. */
+				set_subscription_retry(false);
 			}
 			else
 			{
@@ -1863,6 +1890,9 @@ apply_handle_stream_commit(StringInfo s)
 
 			/* Unlink the files with serialized changes and subxact info. */
 			stream_cleanup_files(MyLogicalRepWorker->subid, xid);
+
+			/* Reset the retry flag. */
+			set_subscription_retry(false);
 			break;
 
 		case TRANS_LEADER_SEND_TO_PARALLEL:
@@ -1893,6 +1923,9 @@ apply_handle_stream_commit(StringInfo s)
 			 * subskiplsn.
 			 */
 			clear_subscription_skip_lsn(commit_data.commit_lsn);
+
+			/* Reset the retry flag. */
+			set_subscription_retry(false);
 			break;
 
 		case TRANS_PARALLEL_APPLY:
@@ -3961,20 +3994,28 @@ start_table_sync(XLogRecPtr *origin_startpos, char **myslotname)
 	}
 	PG_CATCH();
 	{
+		/*
+		 * Emit the error message, and recover from the error state to an idle
+		 * state
+		 */
+		HOLD_INTERRUPTS();
+
+		EmitErrorReport();
+		AbortOutOfAnyTransaction();
+		FlushErrorState();
+
+		RESUME_INTERRUPTS();
+
+		/* Report the worker failed during table synchronization */
+		pgstat_report_subscription_error(MySubscription->oid, false);
+
 		if (MySubscription->disableonerr)
-			DisableSubscriptionAndExit();
-		else
-		{
-			/*
-			 * Report the worker failed during table synchronization. Abort
-			 * the current transaction so that the stats message is sent in an
-			 * idle state.
-			 */
-			AbortOutOfAnyTransaction();
-			pgstat_report_subscription_error(MySubscription->oid, false);
+			DisableSubscriptionOnError();
 
-			PG_RE_THROW();
-		}
+		/* Set the retry flag. */
+		set_subscription_retry(true);
+
+		proc_exit(0);
 	}
 	PG_END_TRY();
 
@@ -3999,20 +4040,27 @@ start_apply(XLogRecPtr origin_startpos)
 	}
 	PG_CATCH();
 	{
+		/*
+		 * Emit the error message, and recover from the error state to an idle
+		 * state
+		 */
+		HOLD_INTERRUPTS();
+
+		EmitErrorReport();
+		AbortOutOfAnyTransaction();
+		FlushErrorState();
+
+		RESUME_INTERRUPTS();
+
+		/* Report the worker failed while applying changes */
+		pgstat_report_subscription_error(MySubscription->oid,
+										 !am_tablesync_worker());
+
 		if (MySubscription->disableonerr)
-			DisableSubscriptionAndExit();
-		else
-		{
-			/*
-			 * Report the worker failed while applying changes. Abort the
-			 * current transaction so that the stats message is sent in an
-			 * idle state.
-			 */
-			AbortOutOfAnyTransaction();
-			pgstat_report_subscription_error(MySubscription->oid, !am_tablesync_worker());
+			DisableSubscriptionOnError();
 
-			PG_RE_THROW();
-		}
+		/* Set the retry flag. */
+		set_subscription_retry(true);
 	}
 	PG_END_TRY();
 }
@@ -4274,39 +4322,20 @@ ApplyWorkerMain(Datum main_arg)
 }
 
 /*
- * After error recovery, disable the subscription in a new transaction
- * and exit cleanly.
+ * Disable the subscription in a new transaction.
  */
 static void
-DisableSubscriptionAndExit(void)
+DisableSubscriptionOnError(void)
 {
-	/*
-	 * Emit the error message, and recover from the error state to an idle
-	 * state
-	 */
-	HOLD_INTERRUPTS();
-
-	EmitErrorReport();
-	AbortOutOfAnyTransaction();
-	FlushErrorState();
-
-	RESUME_INTERRUPTS();
-
-	/* Report the worker failed during either table synchronization or apply */
-	pgstat_report_subscription_error(MyLogicalRepWorker->subid,
-									 !am_tablesync_worker());
-
 	/* Disable the subscription */
 	StartTransactionCommand();
 	DisableSubscription(MySubscription->oid);
 	CommitTransactionCommand();
 
-	/* Notify the subscription has been disabled and exit */
+	/* Notify the subscription has been disabled */
 	ereport(LOG,
 			errmsg("logical replication subscription \"%s\" has been disabled due to an error",
 				   MySubscription->name));
-
-	proc_exit(0);
 }
 
 /*
@@ -4575,3 +4604,67 @@ get_transaction_apply_action(TransactionId xid, ParallelApplyWorkerInfo **winfo)
 	else
 		return TRANS_LEADER_SERIALIZE;
 }
+
+/*
+ * Set subretry of pg_subscription catalog.
+ *
+ * If retry is true, subscriber is about to exit with an error. Otherwise, it
+ * means that the transaction was applied successfully.
+ */
+static void
+set_subscription_retry(bool retry)
+{
+	Relation	rel;
+	HeapTuple	tup;
+	bool		started_tx = false;
+	bool		nulls[Natts_pg_subscription];
+	bool		replaces[Natts_pg_subscription];
+	Datum		values[Natts_pg_subscription];
+
+	/* Fast path - if no state change then nothing to do */
+	if (MySubscription->retry == retry)
+		return;
+
+	/* Fast path - skip for parallel apply workers */
+	if (am_parallel_apply_worker())
+		return;
+
+	if (!IsTransactionState())
+	{
+		StartTransactionCommand();
+		started_tx = true;
+	}
+
+	/* Look up the subscription in the catalog */
+	rel = table_open(SubscriptionRelationId, RowExclusiveLock);
+	tup = SearchSysCacheCopy1(SUBSCRIPTIONOID,
+							  ObjectIdGetDatum(MySubscription->oid));
+
+	if (!HeapTupleIsValid(tup))
+		elog(ERROR, "subscription \"%s\" does not exist", MySubscription->name);
+
+	LockSharedObject(SubscriptionRelationId, MySubscription->oid, 0,
+					 AccessShareLock);
+
+	/* Form a new tuple. */
+	memset(values, 0, sizeof(values));
+	memset(nulls, false, sizeof(nulls));
+	memset(replaces, false, sizeof(replaces));
+
+	/* Set subretry */
+	values[Anum_pg_subscription_subretry - 1] = BoolGetDatum(retry);
+	replaces[Anum_pg_subscription_subretry - 1] = true;
+
+	tup = heap_modify_tuple(tup, RelationGetDescr(rel), values, nulls,
+							replaces);
+
+	/* Update the catalog. */
+	CatalogTupleUpdate(rel, &tup->t_self, tup);
+
+	/* Cleanup. */
+	heap_freetuple(tup);
+	table_close(rel, NoLock);
+
+	if (started_tx)
+		CommitTransactionCommand();
+}
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 026cf46828..067d18c612 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -4507,8 +4507,9 @@ getSubscriptions(Archive *fout)
 	ntups = PQntuples(res);
 
 	/*
-	 * Get subscription fields. We don't include subskiplsn in the dump as
-	 * after restoring the dump this value may no longer be relevant.
+	 * Get subscription fields. We don't include subskiplsn and subretry in
+	 * the dump as after restoring the dump this value may no longer be
+	 * relevant.
 	 */
 	i_tableoid = PQfnumber(res, "tableoid");
 	i_oid = PQfnumber(res, "oid");
diff --git a/src/include/catalog/pg_subscription.h b/src/include/catalog/pg_subscription.h
index b99dddbea4..0864ad6435 100644
--- a/src/include/catalog/pg_subscription.h
+++ b/src/include/catalog/pg_subscription.h
@@ -88,6 +88,8 @@ CATALOG(pg_subscription,6100,SubscriptionRelationId) BKI_SHARED_RELATION BKI_ROW
 	bool		subdisableonerr;	/* True if a worker error should cause the
 									 * subscription to be disabled */
 
+	bool		subretry BKI_DEFAULT(f);	/* True if the previous apply change failed. */
+
 #ifdef CATALOG_VARLEN			/* variable-length fields start here */
 	/* Connection string to the publisher */
 	text		subconninfo BKI_FORCE_NOT_NULL;
@@ -131,6 +133,8 @@ typedef struct Subscription
 	bool		disableonerr;	/* Indicates if the subscription should be
 								 * automatically disabled if a worker error
 								 * occurs */
+	bool		retry;			/* Indicates if the previous apply change
+								 * failed. */
 	char	   *conninfo;		/* Connection string to the publisher */
 	char	   *slotname;		/* Name of the replication slot */
 	char	   *synccommit;		/* Synchronous commit setting for worker */
diff --git a/src/test/subscription/t/015_stream.pl b/src/test/subscription/t/015_stream.pl
index 549f55b80c..742bce091d 100644
--- a/src/test/subscription/t/015_stream.pl
+++ b/src/test/subscription/t/015_stream.pl
@@ -8,51 +8,22 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
-# Check the log that the streamed transaction was completed successfully
-# reported by parallel apply worker.
-sub check_parallel_log
-{
-	my ($node_subscriber, $offset, $is_parallel)= @_;
-	my $parallel_message = 'finished processing the transaction finish command';
-
-	if ($is_parallel)
-	{
-		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
-	}
-}
-
 # Encapsulate all the common test steps which are related to "streaming"
 # parameter so the same code can be run both for the streaming=on and
 # streaming=parallel cases.
 sub test_streaming
 {
-	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
+	my ($node_publisher, $node_subscriber, $appname) = @_;
 
 	# Interleave a pair of transactions, each exceeding the 64kB limit.
 	my $in  = '';
 	my $out = '';
 
-	my $offset = 0;
-
 	my $timer = IPC::Run::timeout($PostgreSQL::Test::Utils::timeout_default);
 
 	my $h = $node_publisher->background_psql('postgres', \$in, \$out, $timer,
 		on_error_stop => 0);
 
-	# If "streaming" parameter is specified as "parallel", we need to check
-	# that streamed transaction was applied using a parallel apply worker.
-	# We have to look for the DEBUG1 log messages about that, so bump up the
-	# log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = debug1");
-		$node_subscriber->reload;
-	}
-
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	$in .= q{
 	BEGIN;
 	INSERT INTO test_tab SELECT i, md5(i::text) FROM generate_series(3, 5000) s(i);
@@ -77,8 +48,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	my $result =
 	  $node_subscriber->safe_psql('postgres',
 		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
@@ -89,9 +58,6 @@ sub test_streaming
 	$node_subscriber->safe_psql('postgres',
 		"ALTER SUBSCRIPTION tap_sub SET (binary = on)");
 
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	# Insert, update and delete enough rows to exceed the 64kB limit.
 	$node_publisher->safe_psql(
 		'postgres', q{
@@ -104,8 +70,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	$result =
 	  $node_subscriber->safe_psql('postgres',
 		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
@@ -120,16 +84,11 @@ sub test_streaming
 		"UPDATE test_tab SET c = 'epoch'::timestamptz + 987654321 * interval '1s'"
 	);
 
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	$node_publisher->safe_psql('postgres',
 		"UPDATE test_tab SET b = md5(a::text)");
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	$result = $node_subscriber->safe_psql('postgres',
 		"SELECT count(*), count(extract(epoch from c) = 987654321), count(d = 999) FROM test_tab"
 	);
@@ -140,14 +99,6 @@ sub test_streaming
 	$node_publisher->safe_psql('postgres',
 		"DELETE FROM test_tab WHERE (a > 2)");
 	$node_publisher->wait_for_catchup($appname);
-
-	# Reset the log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = warning");
-		$node_subscriber->reload;
-	}
 }
 
 # Create publisher node
@@ -195,7 +146,7 @@ my $result =
 	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
 is($result, qq(2|2|2), 'check initial data was copied to subscriber');
 
-test_streaming($node_publisher, $node_subscriber, $appname, 0);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 ######################################
 # Test using streaming mode 'parallel'
@@ -218,7 +169,7 @@ $node_publisher->poll_query_until('postgres',
   or die
   "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
 
-test_streaming($node_publisher, $node_subscriber, $appname, 1);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 $node_subscriber->stop;
 $node_publisher->stop;
diff --git a/src/test/subscription/t/016_stream_subxact.pl b/src/test/subscription/t/016_stream_subxact.pl
index b5156d9750..2beb680661 100644
--- a/src/test/subscription/t/016_stream_subxact.pl
+++ b/src/test/subscription/t/016_stream_subxact.pl
@@ -8,41 +8,12 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
-# Check the log that the streamed transaction was completed successfully
-# reported by parallel apply worker.
-sub check_parallel_log
-{
-	my ($node_subscriber, $offset, $is_parallel)= @_;
-	my $parallel_message = 'finished processing the transaction finish command';
-
-	if ($is_parallel)
-	{
-		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
-	}
-}
-
 # Encapsulate all the common test steps which are related to "streaming"
 # parameter so the same code can be run both for the streaming=on and
 # streaming=parallel cases.
 sub test_streaming
 {
-	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
-
-	my $offset = 0;
-
-	# If "streaming" parameter is specified as "parallel", we need to check
-	# that streamed transaction was applied using a parallel apply worker.
-	# We have to look for the DEBUG1 log messages about that, so bump up the
-	# log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = debug1");
-		$node_subscriber->reload;
-	}
-
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
+	my ($node_publisher, $node_subscriber, $appname) = @_;
 
 	# Insert, update and delete enough rows to exceed 64kB limit.
 	$node_publisher->safe_psql(
@@ -72,8 +43,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	my $result =
 	  $node_subscriber->safe_psql('postgres',
 		"SELECT count(*), count(c), count(d = 999) FROM test_tab");
@@ -86,13 +55,6 @@ sub test_streaming
 		"DELETE FROM test_tab WHERE (a > 2)");
 	$node_publisher->wait_for_catchup($appname);
 
-	# Reset the log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = warning");
-		$node_subscriber->reload;
-	}
 }
 
 # Create publisher node
@@ -140,7 +102,7 @@ my $result =
 	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
 is($result, qq(2|2|2), 'check initial data was copied to subscriber');
 
-test_streaming($node_publisher, $node_subscriber, $appname, 0);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 ######################################
 # Test using streaming mode 'parallel'
@@ -163,7 +125,7 @@ $node_publisher->poll_query_until('postgres',
   or die
   "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
 
-test_streaming($node_publisher, $node_subscriber, $appname, 1);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 $node_subscriber->stop;
 $node_publisher->stop;
diff --git a/src/test/subscription/t/017_stream_ddl.pl b/src/test/subscription/t/017_stream_ddl.pl
index f3c55704cf..43f9ca33b3 100644
--- a/src/test/subscription/t/017_stream_ddl.pl
+++ b/src/test/subscription/t/017_stream_ddl.pl
@@ -8,27 +8,12 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
-# Check the log that the streamed transaction was completed successfully
-# reported by parallel apply worker.
-sub check_parallel_log
-{
-	my ($node_subscriber, $offset, $is_parallel)= @_;
-	my $parallel_message = 'finished processing the transaction finish command';
-
-	if ($is_parallel)
-	{
-		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
-	}
-}
-
 # Encapsulate all the common test steps which are related to "streaming"
 # parameter so the same code can be run both for the streaming=on and
 # streaming=parallel cases.
 sub test_streaming
 {
-	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
-
-	my $offset = 0;
+	my ($node_publisher, $node_subscriber, $appname) = @_;
 
 	# a small (non-streamed) transaction with DDL and DML
 	$node_publisher->safe_psql(
@@ -41,20 +26,6 @@ sub test_streaming
 	COMMIT;
 	});
 
-	# If "streaming" parameter is specified as "parallel", we need to check
-	# that streamed transaction was applied using a parallel apply worker.
-	# We have to look for the DEBUG1 log messages about that, so bump up the
-	# log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = debug1");
-		$node_subscriber->reload;
-	}
-
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	# large (streamed) transaction with DDL and DML
 	$node_publisher->safe_psql(
 		'postgres', q{
@@ -79,8 +50,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	my $result =
 	  $node_subscriber->safe_psql('postgres',
 		"SELECT count(*), count(c), count(d), count(e) FROM test_tab");
@@ -88,9 +57,6 @@ sub test_streaming
 		'check data was copied to subscriber in streaming mode and extra columns contain local defaults'
 	);
 
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	# A large (streamed) transaction with DDL and DML. One of the DDL is performed
 	# after DML to ensure that we invalidate the schema sent for test_tab so that
 	# the next transaction has to send the schema again.
@@ -113,8 +79,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	$result = $node_subscriber->safe_psql('postgres',
 		"SELECT count(*), count(c), count(d), count(e), count(f) FROM test_tab"
 	);
@@ -129,14 +93,6 @@ sub test_streaming
 	ALTER TABLE test_tab DROP COLUMN c, DROP COLUMN d, DROP COLUMN e, DROP COLUMN f;
 	});
 	$node_publisher->wait_for_catchup($appname);
-
-	# Reset the log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = warning");
-		$node_subscriber->reload;
-	}
 }
 
 # Create publisher node
@@ -184,7 +140,7 @@ my $result =
 	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
 is($result, qq(2|0|0), 'check initial data was copied to subscriber');
 
-test_streaming($node_publisher, $node_subscriber, $appname, 0);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 ######################################
 # Test using streaming mode 'parallel'
@@ -202,7 +158,7 @@ $node_publisher->poll_query_until('postgres',
   or die
   "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
 
-test_streaming($node_publisher, $node_subscriber, $appname, 1);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 $node_subscriber->stop;
 $node_publisher->stop;
diff --git a/src/test/subscription/t/018_stream_subxact_abort.pl b/src/test/subscription/t/018_stream_subxact_abort.pl
index f74542c2e9..67c778dcfa 100644
--- a/src/test/subscription/t/018_stream_subxact_abort.pl
+++ b/src/test/subscription/t/018_stream_subxact_abort.pl
@@ -8,41 +8,12 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
-# Check the log that the streamed transaction was completed successfully
-# reported by parallel apply worker.
-sub check_parallel_log
-{
-	my ($node_subscriber, $offset, $is_parallel)= @_;
-	my $parallel_message = 'finished processing the transaction finish command';
-
-	if ($is_parallel)
-	{
-		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
-	}
-}
-
 # Encapsulate all the common test steps which are related to "streaming"
 # parameter so the same code can be run both for the streaming=on and
 # streaming=parallel cases.
 sub test_streaming
 {
-	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
-
-	my $offset = 0;
-
-	# If "streaming" parameter is specified as "parallel", we need to check
-	# that streamed transaction was applied using a parallel apply worker.
-	# We have to look for the DEBUG1 log messages about that, so bump up the
-	# log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = debug1");
-		$node_subscriber->reload;
-	}
-
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
+	my ($node_publisher, $node_subscriber, $appname) = @_;
 
 	# large (streamed) transaction with DDL, DML and ROLLBACKs
 	$node_publisher->safe_psql(
@@ -68,8 +39,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	my $result =
 	  $node_subscriber->safe_psql('postgres',
 		"SELECT count(*), count(c) FROM test_tab");
@@ -77,9 +46,6 @@ sub test_streaming
 		'check rollback to savepoint was reflected on subscriber and extra columns contain local defaults'
 	);
 
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	# large (streamed) transaction with subscriber receiving out of order
 	# subtransaction ROLLBACKs
 	$node_publisher->safe_psql(
@@ -100,17 +66,12 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	$result =
 	  $node_subscriber->safe_psql('postgres',
 		"SELECT count(*), count(c) FROM test_tab");
 	is($result, qq(2500|0),
 		'check rollback to savepoint was reflected on subscriber');
 
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	# large (streamed) transaction with subscriber receiving rollback
 	$node_publisher->safe_psql(
 		'postgres', q{
@@ -125,8 +86,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	$result =
 	  $node_subscriber->safe_psql('postgres',
 		"SELECT count(*), count(c) FROM test_tab");
@@ -136,14 +95,6 @@ sub test_streaming
 	$node_publisher->safe_psql('postgres',
 		"DELETE FROM test_tab WHERE (a > 2)");
 	$node_publisher->wait_for_catchup($appname);
-
-	# Reset the log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = warning");
-		$node_subscriber->reload;
-	}
 }
 
 # Create publisher node
@@ -190,7 +141,7 @@ my $result =
 	"SELECT count(*), count(c) FROM test_tab");
 is($result, qq(2|0), 'check initial data was copied to subscriber');
 
-test_streaming($node_publisher, $node_subscriber, $appname, 0);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 ######################################
 # Test using streaming mode 'parallel'
@@ -208,7 +159,7 @@ $node_publisher->poll_query_until('postgres',
   or die
   "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
 
-test_streaming($node_publisher, $node_subscriber, $appname, 1);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 $node_subscriber->stop;
 $node_publisher->stop;
diff --git a/src/test/subscription/t/019_stream_subxact_ddl_abort.pl b/src/test/subscription/t/019_stream_subxact_ddl_abort.pl
index b6f3a60682..41ec1e8916 100644
--- a/src/test/subscription/t/019_stream_subxact_ddl_abort.pl
+++ b/src/test/subscription/t/019_stream_subxact_ddl_abort.pl
@@ -9,41 +9,12 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
-# Check the log that the streamed transaction was completed successfully
-# reported by parallel apply worker.
-sub check_parallel_log
-{
-	my ($node_subscriber, $offset, $is_parallel)= @_;
-	my $parallel_message = 'finished processing the transaction finish command';
-
-	if ($is_parallel)
-	{
-		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
-	}
-}
-
 # Encapsulate all the common test steps which are related to "streaming"
 # parameter so the same code can be run both for the streaming=on and
 # streaming=parallel cases.
 sub test_streaming
 {
-	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
-
-	my $offset = 0;
-
-	# If "streaming" parameter is specified as "parallel", we need to check
-	# that streamed transaction was applied using a parallel apply worker.
-	# We have to look for the DEBUG1 log messages about that, so bump up the
-	# log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = debug1");
-		$node_subscriber->reload;
-	}
-
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
+	my ($node_publisher, $node_subscriber, $appname) = @_;
 
 	# large (streamed) transaction with DDL, DML and ROLLBACKs
 	$node_publisher->safe_psql(
@@ -67,8 +38,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	my $result =
 	  $node_subscriber->safe_psql('postgres',
 		"SELECT count(*), count(c) FROM test_tab");
@@ -83,14 +52,6 @@ sub test_streaming
 	ALTER TABLE test_tab DROP COLUMN c;
 	});
 	$node_publisher->wait_for_catchup($appname);
-
-	# Reset the log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = warning");
-		$node_subscriber->reload;
-	}
 }
 
 # Create publisher node
@@ -137,7 +98,7 @@ my $result =
 	"SELECT count(*), count(c) FROM test_tab");
 is($result, qq(2|0), 'check initial data was copied to subscriber');
 
-test_streaming($node_publisher, $node_subscriber, $appname, 0);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 ######################################
 # Test using streaming mode 'parallel'
@@ -155,7 +116,7 @@ $node_publisher->poll_query_until('postgres',
   or die
   "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
 
-test_streaming($node_publisher, $node_subscriber, $appname, 1);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 $node_subscriber->stop;
 $node_publisher->stop;
diff --git a/src/test/subscription/t/022_twophase_cascade.pl b/src/test/subscription/t/022_twophase_cascade.pl
index 8c704969ce..e8f20734b7 100644
--- a/src/test/subscription/t/022_twophase_cascade.pl
+++ b/src/test/subscription/t/022_twophase_cascade.pl
@@ -11,19 +11,6 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
-# Check the log that the streamed transaction was completed successfully
-# reported by parallel apply worker.
-sub check_parallel_log
-{
-	my ($node_subscriber, $offset, $streaming_mode)= @_;
-	my $parallel_message = 'finished processing the transaction finish command';
-
-	if ($streaming_mode eq 'parallel')
-	{
-		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
-	}
-}
-
 # Encapsulate all the common test steps which are related to "streaming" parameter
 # so the same code can be run both for the streaming=on and streaming=parallel
 # cases.
@@ -32,9 +19,6 @@ sub test_streaming
 	my ($node_A, $node_B, $node_C, $appname_B, $appname_C, $streaming_mode) =
 	  @_;
 
-	my $offset_B = 0;
-	my $offset_C = 0;
-
 	my $oldpid_B = $node_A->safe_psql(
 		'postgres', "
 		SELECT pid FROM pg_stat_replication
@@ -76,23 +60,6 @@ sub test_streaming
 	# Expect all data is replicated on subscriber(s) after the commit.
 	###############################
 
-	# If "streaming" parameter is specified as "parallel", we need to check
-	# that streamed transaction was prepared using a parallel apply worker.
-	# We have to look for the DEBUG1 log messages about that, so bump up the
-	# log verbosity.
-	if ($streaming_mode eq 'parallel')
-	{
-		$node_B->append_conf('postgresql.conf', "log_min_messages = debug1");
-		$node_B->reload;
-
-		$node_C->append_conf('postgresql.conf', "log_min_messages = debug1");
-		$node_C->reload;
-	}
-
-	# Check the subscriber log from now on.
-	$offset_B = -s $node_B->logfile;
-	$offset_C = -s $node_C->logfile;
-
 	# Insert, update and delete enough rows to exceed the 64kB limit.
 	# Then 2PC PREPARE
 	$node_A->safe_psql(
@@ -106,9 +73,6 @@ sub test_streaming
 	$node_A->wait_for_catchup($appname_B);
 	$node_B->wait_for_catchup($appname_C);
 
-	check_parallel_log($node_B, $offset_B, $streaming_mode);
-	check_parallel_log($node_C, $offset_C, $streaming_mode);
-
 	# check the transaction state is prepared on subscriber(s)
 	my $result =
 	  $node_B->safe_psql('postgres',
@@ -162,10 +126,6 @@ sub test_streaming
 	# First, delete the data except for 2 rows (delete will be replicated)
 	$node_A->safe_psql('postgres', "DELETE FROM test_tab WHERE a > 2;");
 
-	# Check the subscriber log from now on.
-	$offset_B = -s $node_B->logfile;
-	$offset_C = -s $node_C->logfile;
-
 	# 2PC PREPARE with a nested ROLLBACK TO SAVEPOINT
 	$node_A->safe_psql(
 		'postgres', "
@@ -182,9 +142,6 @@ sub test_streaming
 	$node_A->wait_for_catchup($appname_B);
 	$node_B->wait_for_catchup($appname_C);
 
-	check_parallel_log($node_B, $offset_B, $streaming_mode);
-	check_parallel_log($node_C, $offset_C, $streaming_mode);
-
 	# check the transaction state prepared on subscriber(s)
 	$result =
 	  $node_B->safe_psql('postgres',
@@ -231,16 +188,6 @@ sub test_streaming
 	$node_A->safe_psql('postgres', "DELETE FROM test_tab WHERE a > 2;");
 	$node_A->wait_for_catchup($appname_B);
 	$node_B->wait_for_catchup($appname_C);
-
-	# Reset the log verbosity.
-	if ($streaming_mode eq 'parallel')
-	{
-		$node_B->append_conf('postgresql.conf', "log_min_messages = warning");
-		$node_B->reload;
-
-		$node_C->append_conf('postgresql.conf', "log_min_messages = warning");
-		$node_C->reload;
-	}
 }
 
 ###############################
diff --git a/src/test/subscription/t/023_twophase_stream.pl b/src/test/subscription/t/023_twophase_stream.pl
index fc96999706..c49cb10611 100644
--- a/src/test/subscription/t/023_twophase_stream.pl
+++ b/src/test/subscription/t/023_twophase_stream.pl
@@ -8,27 +8,12 @@ use PostgreSQL::Test::Cluster;
 use PostgreSQL::Test::Utils;
 use Test::More;
 
-# Check the log that the streamed transaction was completed successfully
-# reported by parallel apply worker.
-sub check_parallel_log
-{
-	my ($node_subscriber, $offset, $is_parallel)= @_;
-	my $parallel_message = 'finished processing the transaction finish command';
-
-	if ($is_parallel)
-	{
-		$node_subscriber->wait_for_log(qr/$parallel_message/, $offset);
-	}
-}
-
 # Encapsulate all the common test steps which are related to "streaming"
 # parameter so the same code can be run both for the streaming=on and
 # streaming=parallel cases.
 sub test_streaming
 {
-	my ($node_publisher, $node_subscriber, $appname, $is_parallel) = @_;
-
-	my $offset = 0;
+	my ($node_publisher, $node_subscriber, $appname) = @_;
 
 	###############################
 	# Test 2PC PREPARE / COMMIT PREPARED.
@@ -38,20 +23,6 @@ sub test_streaming
 	# Expect all data is replicated on subscriber side after the commit.
 	###############################
 
-	# If "streaming" parameter is specified as "parallel", we need to check
-	# that streamed transaction was prepared using a parallel apply worker.
-	# We have to look for the DEBUG1 log messages about that, so bump up the
-	# log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = debug1");
-		$node_subscriber->reload;
-	}
-
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	# check that 2PC gets replicated to subscriber
 	# Insert, update and delete enough rows to exceed the 64kB limit.
 	$node_publisher->safe_psql(
@@ -64,8 +35,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	# check that transaction is in prepared state on subscriber
 	my $result = $node_subscriber->safe_psql('postgres',
 		"SELECT count(*) FROM pg_prepared_xacts;");
@@ -100,9 +69,6 @@ sub test_streaming
 	$node_publisher->safe_psql('postgres',
 		"DELETE FROM test_tab WHERE a > 2;");
 
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	# Then insert, update and delete enough rows to exceed the 64kB limit.
 	$node_publisher->safe_psql(
 		'postgres', q{
@@ -114,8 +80,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	# check that transaction is in prepared state on subscriber
 	$result = $node_subscriber->safe_psql('postgres',
 		"SELECT count(*) FROM pg_prepared_xacts;");
@@ -148,9 +112,6 @@ sub test_streaming
 	# Note: both publisher and subscriber do crash/restart.
 	###############################
 
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	$node_publisher->safe_psql(
 		'postgres', q{
 		BEGIN;
@@ -165,8 +126,6 @@ sub test_streaming
 	$node_publisher->start;
 	$node_subscriber->start;
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	# commit post the restart
 	$node_publisher->safe_psql('postgres',
 		"COMMIT PREPARED 'test_prepared_tab';");
@@ -194,9 +153,6 @@ sub test_streaming
 	$node_publisher->safe_psql('postgres',
 		"DELETE FROM test_tab WHERE a > 2;");
 
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	# Then insert, update and delete enough rows to exceed the 64kB limit.
 	$node_publisher->safe_psql(
 		'postgres', q{
@@ -208,8 +164,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	# check that transaction is in prepared state on subscriber
 	$result = $node_subscriber->safe_psql('postgres',
 		"SELECT count(*) FROM pg_prepared_xacts;");
@@ -252,9 +206,6 @@ sub test_streaming
 	$node_publisher->safe_psql('postgres',
 		"DELETE FROM test_tab WHERE a > 2;");
 
-	# Check the subscriber log from now on.
-	$offset = -s $node_subscriber->logfile;
-
 	# Then insert, update and delete enough rows to exceed the 64kB limit.
 	$node_publisher->safe_psql(
 		'postgres', q{
@@ -266,8 +217,6 @@ sub test_streaming
 
 	$node_publisher->wait_for_catchup($appname);
 
-	check_parallel_log($node_subscriber, $offset, $is_parallel);
-
 	# check that transaction is in prepared state on subscriber
 	$result = $node_subscriber->safe_psql('postgres',
 		"SELECT count(*) FROM pg_prepared_xacts;");
@@ -299,14 +248,6 @@ sub test_streaming
 	$node_publisher->safe_psql('postgres',
 		"DELETE FROM test_tab WHERE a > 2;");
 	$node_publisher->wait_for_catchup($appname);
-
-	# Reset the log verbosity.
-	if ($is_parallel)
-	{
-		$node_subscriber->append_conf('postgresql.conf',
-			"log_min_messages = warning");
-		$node_subscriber->reload;
-	}
 }
 
 ###############################
@@ -374,7 +315,7 @@ my $result = $node_subscriber->safe_psql('postgres',
 	"SELECT count(*), count(c), count(d = 999) FROM test_tab");
 is($result, qq(2|2|2), 'check initial data was copied to subscriber');
 
-test_streaming($node_publisher, $node_subscriber, $appname, 0);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 ######################################
 # Test using streaming mode 'parallel'
@@ -397,7 +338,7 @@ $node_publisher->poll_query_until('postgres',
   or die
   "Timed out while waiting for apply to restart after changing SUBSCRIPTION";
 
-test_streaming($node_publisher, $node_subscriber, $appname, 1);
+test_streaming($node_publisher, $node_subscriber, $appname);
 
 ###############################
 # check all the cleanup
diff --git a/src/test/subscription/t/032_streaming_parallel_safety.pl b/src/test/subscription/t/032_streaming_parallel_safety.pl
index 6fdbea36c6..a7bbf6ff46 100644
--- a/src/test/subscription/t/032_streaming_parallel_safety.pl
+++ b/src/test/subscription/t/032_streaming_parallel_safety.pl
@@ -81,7 +81,8 @@ my $h = $node_publisher->background_psql('postgres', \$in, \$out, $timer,
 # ============================================================================
 # It is not allowed that the unique column in the relation on the
 # subscriber-side is not the unique column on the publisher-side. Check the
-# error reported by parallel worker in this case.
+# error reported by parallel worker in this case. And after retrying in
+# apply worker, we check if the data is replicated successfully.
 # ============================================================================
 
 # First we check the unique index on normal table.
@@ -106,6 +107,10 @@ $node_subscriber->wait_for_log(
 	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
 	$offset);
 
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? duplicate key value violates unique constraint "idx_tab1"/,
+	$offset);
+
 # Drop the unique index on the subscriber, now it works.
 $node_subscriber->safe_psql('postgres', "DROP INDEX idx_tab1");
 
@@ -114,7 +119,7 @@ $node_publisher->wait_for_catchup($appname);
 
 my $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
-is($result, qq(5001), 'data replicated to subscriber after dropping index');
+is($result, qq(5001), 'data replicated to subscriber after dropping unique index to retry apply');
 
 # Clean up test data from the environment.
 $node_publisher->safe_psql('postgres', "TRUNCATE TABLE test_tab1");
@@ -135,19 +140,21 @@ $node_subscriber->wait_for_log(
 	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab_partitioned" using subscription parameter streaming = parallel/,
 	$offset);
 
-# Drop the unique index on the subscriber, now it works.
-$node_subscriber->safe_psql('postgres', "DROP INDEX test_tab_b_partition_idx");
-
 # Wait for this streaming transaction to be applied in the apply worker.
 $node_publisher->wait_for_catchup($appname);
 
 $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab_partitioned");
-is($result, qq(5000), 'data replicated to subscriber after dropping index');
+is($result, qq(5000), 'data replicated to subscriber after retrying because of unique index');
+
+# Drop the unique index on the subscriber.
+$node_subscriber->safe_psql('postgres', "DROP INDEX test_tab_b_partition_idx");
 
 # ============================================================================
 # Triggers which execute non-immutable function are not allowed on the
 # subscriber side. Check the error reported by parallel worker in this case.
+# And after retrying in apply worker, we check if the data is replicated
+# successfully.
 # ============================================================================
 
 # First we check the trigger function on normal table.
@@ -168,17 +175,6 @@ CREATE TRIGGER tri_tab1_unsafe
 BEFORE INSERT ON public.test_tab1
 FOR EACH ROW EXECUTE PROCEDURE trigger_func_tab1_unsafe();
 ALTER TABLE test_tab1 ENABLE REPLICA TRIGGER tri_tab1_unsafe;
-
-CREATE FUNCTION trigger_func_tab1_safe() RETURNS TRIGGER AS \$\$
-  BEGIN
-    RAISE NOTICE 'test for safe trigger function';
-	RETURN NEW;
-  END
-\$\$ language plpgsql;
-ALTER FUNCTION trigger_func_tab1_safe IMMUTABLE;
-CREATE TRIGGER tri_tab1_safe
-BEFORE INSERT ON public.test_tab1
-FOR EACH ROW EXECUTE PROCEDURE trigger_func_tab1_safe();
 });
 
 # Check the subscriber log from now on.
@@ -203,27 +199,25 @@ $node_subscriber->wait_for_log(
 	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
 	$offset);
 
-# Using trigger with immutable function, now it works.
-$node_subscriber->safe_psql(
-	'postgres', qq{
-ALTER TABLE test_tab1 ENABLE REPLICA TRIGGER tri_tab1_safe;
-DROP TRIGGER tri_tab1_unsafe ON public.test_tab1;
-});
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? duplicate key value violates unique constraint "idx_tab2"/,
+	$offset);
+
+# Drop the unique index on the subscriber, now it works.
+$node_subscriber->safe_psql('postgres', "DROP INDEX idx_tab2");
 
 # Wait for this streaming transaction to be applied in the apply worker.
 $node_publisher->wait_for_catchup($appname);
 
 $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
-is($result, qq(2), 'data replicated to subscriber after using immutable expression');
+is($result, qq(2), 'data replicated to subscriber after retrying because of trigger');
 
 # Clean up test data from the environment.
 $node_subscriber->safe_psql(
 	'postgres', qq{
-DROP INDEX idx_tab2;
-DROP TRIGGER tri_tab1_safe ON public.test_tab1;
+DROP TRIGGER tri_tab1_unsafe ON public.test_tab1;
 DROP function trigger_func_tab1_unsafe;
-DROP function trigger_func_tab1_safe;
 });
 $node_publisher->safe_psql(
 	'postgres', qq{
@@ -256,21 +250,22 @@ $node_subscriber->wait_for_log(
 	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab_partitioned" using subscription parameter streaming = parallel/,
 	$offset);
 
-# Drop the trigger on the subscriber, now it works.
-$node_subscriber->safe_psql('postgres',
-	"DROP TRIGGER insert_trig ON test_tab_partition");
-
 # Wait for this streaming transaction to be applied in the apply worker.
 $node_publisher->wait_for_catchup($appname);
 
 $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab_partitioned");
-is($result, qq(0), 'data replicated to subscriber after dropping trigger');
+is($result, qq(0), 'data replicated to subscriber after retrying because of trigger');
+
+# Drop the trigger on the subscriber.
+$node_subscriber->safe_psql('postgres',
+	"DROP TRIGGER insert_trig ON test_tab_partition");
 
 # ============================================================================
 # It is not allowed that column default value expression contains a
 # non-immutable function on the subscriber side. Check the error reported by
-# parallel worker in this case.
+# parallel worker in this case. And after retrying in apply worker, we check
+# if the data is replicated successfully.
 # ============================================================================
 
 # First we check the column default value expression on normal table.
@@ -308,17 +303,13 @@ $node_subscriber->wait_for_log(
 	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
 	$offset);
 
-# Alter default values to immutable expression, now it works.
-$node_subscriber->safe_psql('postgres',
-	"ALTER TABLE test_tab1 ALTER COLUMN b SET DEFAULT 1");
-
 # Wait for this streaming transaction to be applied in the apply worker.
 $node_publisher->wait_for_catchup($appname);
 
 $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
 is($result, qq(5001),
-	'data replicated to subscriber after using immutable expression');
+	'data replicated to subscriber after retrying because of column default value');
 
 # Clean up test data from the environment.
 $node_subscriber->safe_psql('postgres', "ALTER TABLE test_tab1 DROP COLUMN b");
@@ -344,22 +335,23 @@ $node_subscriber->wait_for_log(
 	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab_partitioned" using subscription parameter streaming = parallel/,
 	$offset);
 
-# Drop default value on the subscriber, now it works.
-$node_subscriber->safe_psql('postgres',
-	"ALTER TABLE test_tab_partition ALTER COLUMN b DROP DEFAULT");
-
 # Wait for this streaming transaction to be applied in the apply worker.
 $node_publisher->wait_for_catchup($appname);
 
 $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab_partitioned");
 is($result, qq(5000),
-	'data replicated to subscriber after dropping default value expression');
+	'data replicated to subscriber after retrying because of column default value');
+
+# Drop default value on the subscriber.
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE test_tab_partition ALTER COLUMN b DROP DEFAULT");
 
 # ============================================================================
 # It is not allowed that domain constraint expression contains a non-immutable
 # function on the subscriber side. Check the error reported by parallel
-# worker in this case.
+# worker in this case. And after retrying in apply worker, we check if the
+# data is replicated successfully.
 # ============================================================================
 
 # Because the column type of the partition table must be the same as its parent
@@ -400,17 +392,13 @@ $node_subscriber->wait_for_log(
 	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
 	$offset);
 
-# Drop domain constraint expression, now it works.
-$node_subscriber->safe_psql('postgres',
-	"ALTER DOMAIN tmp_domain DROP CONSTRAINT domain_check");
-
 # Wait for this streaming transaction to be applied in the apply worker.
 $node_publisher->wait_for_catchup($appname);
 
 $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
 is($result, qq(5001),
-	'data replicated to subscriber after using immutable expression'
+	'data replicated to subscriber after retrying because of domain'
 );
 
 # Clean up test data from the environment.
@@ -424,9 +412,10 @@ TRUNCATE TABLE test_tab2;
 $node_publisher->wait_for_catchup($appname);
 
 # ============================================================================
-# It is not allowed that constraint expression contains a non-immutable function
-# on the subscriber side. Check the error reported by parallel worker in this
-# case.
+# It is not allowed that constraint expression contains a non-immutable
+# function on the subscriber side. Check the error reported by parallel
+# worker in this case. And after retrying in apply worker, we check if the
+# data is replicated successfully.
 # ============================================================================
 
 # First we check the constraint expression on normal table.
@@ -459,23 +448,16 @@ $node_subscriber->wait_for_log(
 	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
 	$offset);
 
-# Alter constraint expression to immutable expression, now it works.
-$node_subscriber->safe_psql(
-	'postgres', qq{
-ALTER TABLE test_tab1 DROP CONSTRAINT const_tab1_unsafe;
-ALTER TABLE test_tab1 ADD CONSTRAINT const_tab1_safe CHECK(a >= 0);
-});
-
 # Wait for this streaming transaction to be applied in the apply worker.
 $node_publisher->wait_for_catchup($appname);
 
 $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
 is($result, qq(5001),
-	'data replicated to subscriber after using immutable expression');
+	'data replicated to subscriber after retrying because of constraint');
 
 # Clean up test data from the environment.
-$node_subscriber->safe_psql('postgres', "ALTER TABLE test_tab1 DROP CONSTRAINT const_tab1_safe");
+$node_subscriber->safe_psql('postgres', "ALTER TABLE test_tab1 DROP CONSTRAINT const_tab1_unsafe");
 $node_publisher->safe_psql(
 	'postgres', qq{
 TRUNCATE TABLE test_tab1;
@@ -498,21 +480,22 @@ $node_subscriber->wait_for_log(
 	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab_partitioned" using subscription parameter streaming = parallel/,
 	$offset);
 
-# Drop constraint on the subscriber, now it works.
-$node_subscriber->safe_psql('postgres',
-	"ALTER TABLE test_tab_partition DROP CONSTRAINT test_tab_con");
-
 # Wait for this streaming transaction to be applied in the apply worker.
 $node_publisher->wait_for_catchup($appname);
 
 $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab_partitioned");
 is($result, qq(0),
-	'data replicated to subscriber after dropping constraint expression');
+	'data replicated to subscriber after retrying because of constraint');
+
+# Drop constraint on the subscriber.
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE test_tab_partition DROP CONSTRAINT test_tab_con");
 
 # ============================================================================
 # It is not allowed that foreign key on the subscriber side. Check the error
-# reported by parallel worker in this case.
+# reported by parallel worker in this case. And after retrying in apply
+# worker, we check if the data is replicated successfully.
 # ============================================================================
 
 # First we check the foreign key on normal table.
@@ -553,8 +536,13 @@ $node_subscriber->wait_for_log(
 	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab1" using subscription parameter streaming = parallel/,
 	$offset);
 
-# Drop the foreign key constraint on the subscriber, now it works.
-$node_subscriber->safe_psql('postgres', "ALTER TABLE test_tab1 DROP CONSTRAINT test_tab1fk");
+# Wait for error log to make sure the dependent data has been deleted.
+$node_subscriber->wait_for_log(
+	qr/ERROR: ( [A-Z0-9]+:)? insert or update on table "test_tab1" violates foreign key constraint "test_tab1fk"/,
+	$offset);
+
+# Insert dependent data on the publisher, now it works.
+$node_subscriber->safe_psql('postgres', "INSERT INTO test_tab2 VALUES(1)");
 
 # Wait for this streaming transaction to be applied in the apply worker.
 $node_publisher->wait_for_catchup($appname);
@@ -562,9 +550,10 @@ $node_publisher->wait_for_catchup($appname);
 $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab1");
 is($result, qq(1),
-	'data replicated to subscriber after dropping the foreign key');
+	'data replicated to subscriber after retrying because of foreign key');
 
 # Clean up test data from the environment.
+$node_subscriber->safe_psql('postgres', "ALTER TABLE test_tab1 DROP CONSTRAINT test_tab1fk");
 $node_publisher->safe_psql(
 	'postgres', qq{
 TRUNCATE TABLE test_tab1;
@@ -576,6 +565,7 @@ $node_publisher->wait_for_catchup($appname);
 $node_subscriber->safe_psql(
 	'postgres', qq{
 CREATE TABLE test_tab_partition_f (a int primary key);
+INSERT INTO test_tab_partition_f SELECT i  FROM generate_series(1, 5000) s(i);
 ALTER TABLE test_tab_partition ADD CONSTRAINT test_tab_patition_fk FOREIGN KEY(a) REFERENCES test_tab_partition_f(a);
 SELECT 'ALTER TABLE test_tab_partition ENABLE REPLICA TRIGGER "' || tgname || '"' FROM pg_trigger WHERE tgrelid = 'test_tab_partition'::regclass::oid \\gexec
 });
@@ -591,17 +581,17 @@ $node_subscriber->wait_for_log(
 	qr/ERROR: ( [A-Z0-9]+:)? cannot replicate target relation "public.test_tab_partitioned" using subscription parameter streaming = parallel/,
 	$offset);
 
-# Drop the foreign key constraint on the subscriber, now it works.
-$node_subscriber->safe_psql('postgres',
-	"ALTER TABLE test_tab_partition DROP CONSTRAINT test_tab_patition_fk");
-
 # Wait for this streaming transaction to be applied in the apply worker.
 $node_publisher->wait_for_catchup($appname);
 
 $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM test_tab_partitioned");
 is($result, qq(5000),
-	'data replicated to subscriber after dropping the foreign key');
+	'data replicated to subscribers after retrying because of foreign key');
+
+# Drop the foreign key constraint on the subscriber.
+$node_subscriber->safe_psql('postgres',
+	"ALTER TABLE test_tab_partition DROP CONSTRAINT test_tab_patition_fk");
 
 $node_subscriber->stop;
 $node_publisher->stop;
-- 
2.23.0.windows.1



  [application/octet-stream] v29-0005-Add-a-main_worker_pid-to-pg_stat_subscription.patch (7.7K, ../OS3PR01MB6275F145878B4A44586C46CE9E499@OS3PR01MB6275.jpnprd01.prod.outlook.com/6-v29-0005-Add-a-main_worker_pid-to-pg_stat_subscription.patch)
  download | inline diff:
From 522583229cb1c4c315ce31e0ff70ab526cbfcabb Mon Sep 17 00:00:00 2001
From: "houzj.fnst" <[email protected]>
Date: Thu, 11 Aug 2022 11:49:08 +0800
Subject: [PATCH v29 5/5] Add a main_worker_pid to pg_stat_subscription

main_worker_pid is Process ID of the leader apply worker, if this process is a
apply parallel worker. NULL if this process is a leader apply worker or a
synchronization worker.

The new column can make it easier to distinguish leader apply worker and apply
parallel worker which is also similar to the 'leader_pid' column in
pg_stat_activity.
---
 doc/src/sgml/monitoring.sgml               | 21 ++++++++++++----
 src/backend/catalog/system_views.sql       |  1 +
 src/backend/replication/logical/launcher.c | 28 +++++++++++++---------
 src/include/catalog/pg_proc.dat            |  6 ++---
 src/test/regress/expected/rules.out        |  3 ++-
 5 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 1d9509a2f6..4591ffe91f 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -3178,13 +3178,24 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       </para></entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>apply_leader_pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of the leader apply worker, if this process is a apply
+       parallel worker. NULL if this process is a leader apply worker or a
+       synchronization worker.
+      </para></entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry"><para role="column_definition">
        <structfield>relid</structfield> <type>oid</type>
       </para>
       <para>
        OID of the relation that the worker is synchronizing; null for the
-       main apply worker
+       main apply worker and the apply parallel worker
       </para></entry>
      </row>
 
@@ -3194,7 +3205,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       </para>
       <para>
        Last write-ahead log location received, the initial value of
-       this field being 0
+       this field being 0; null for the apply parallel worker
       </para></entry>
      </row>
 
@@ -3203,7 +3214,8 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>last_msg_send_time</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Send time of last message received from origin WAL sender
+       Send time of last message received from origin WAL sender; null for the
+       apply parallel worker
       </para></entry>
      </row>
 
@@ -3212,7 +3224,8 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>last_msg_receipt_time</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Receipt time of last message received from origin WAL sender
+       Receipt time of last message received from origin WAL sender; null for
+       the apply parallel worker
       </para></entry>
      </row>
 
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index f4a00496ee..3f15cf24e9 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -946,6 +946,7 @@ CREATE VIEW pg_stat_subscription AS
             su.oid AS subid,
             su.subname,
             st.pid,
+            st.apply_leader_pid,
             st.relid,
             st.received_lsn,
             st.last_msg_send_time,
diff --git a/src/backend/replication/logical/launcher.c b/src/backend/replication/logical/launcher.c
index 8344e4509b..87142b3925 100644
--- a/src/backend/replication/logical/launcher.c
+++ b/src/backend/replication/logical/launcher.c
@@ -1046,7 +1046,7 @@ IsLogicalLauncher(void)
 Datum
 pg_stat_get_subscription(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_SUBSCRIPTION_COLS	8
+#define PG_STAT_GET_SUBSCRIPTION_COLS	9
 	Oid			subid = PG_ARGISNULL(0) ? InvalidOid : PG_GETARG_OID(0);
 	int			i;
 	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
@@ -1080,26 +1080,32 @@ pg_stat_get_subscription(PG_FUNCTION_ARGS)
 		else
 			nulls[1] = true;
 		values[2] = Int32GetDatum(worker_pid);
-		if (XLogRecPtrIsInvalid(worker.last_lsn))
+
+		if (worker.apply_leader_pid == 0)
 			nulls[3] = true;
 		else
-			values[3] = LSNGetDatum(worker.last_lsn);
-		if (worker.last_send_time == 0)
+			values[3] = Int32GetDatum(worker.apply_leader_pid);
+
+		if (XLogRecPtrIsInvalid(worker.last_lsn))
 			nulls[4] = true;
 		else
-			values[4] = TimestampTzGetDatum(worker.last_send_time);
-		if (worker.last_recv_time == 0)
+			values[4] = LSNGetDatum(worker.last_lsn);
+		if (worker.last_send_time == 0)
 			nulls[5] = true;
 		else
-			values[5] = TimestampTzGetDatum(worker.last_recv_time);
-		if (XLogRecPtrIsInvalid(worker.reply_lsn))
+			values[5] = TimestampTzGetDatum(worker.last_send_time);
+		if (worker.last_recv_time == 0)
 			nulls[6] = true;
 		else
-			values[6] = LSNGetDatum(worker.reply_lsn);
-		if (worker.reply_time == 0)
+			values[6] = TimestampTzGetDatum(worker.last_recv_time);
+		if (XLogRecPtrIsInvalid(worker.reply_lsn))
 			nulls[7] = true;
 		else
-			values[7] = TimestampTzGetDatum(worker.reply_time);
+			values[7] = LSNGetDatum(worker.reply_lsn);
+		if (worker.reply_time == 0)
+			nulls[8] = true;
+		else
+			values[8] = TimestampTzGetDatum(worker.reply_time);
 
 		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc,
 							 values, nulls);
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index a07e737a33..6b18f775a5 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5393,9 +5393,9 @@
   proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',
   proretset => 't', provolatile => 's', proparallel => 'r',
   prorettype => 'record', proargtypes => 'oid',
-  proallargtypes => '{oid,oid,oid,int4,pg_lsn,timestamptz,timestamptz,pg_lsn,timestamptz}',
-  proargmodes => '{i,o,o,o,o,o,o,o,o}',
-  proargnames => '{subid,subid,relid,pid,received_lsn,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time}',
+  proallargtypes => '{oid,oid,oid,int4,int4,pg_lsn,timestamptz,timestamptz,pg_lsn,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o,o,o,o,o}',
+  proargnames => '{subid,subid,relid,pid,apply_leader_pid,received_lsn,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time}',
   prosrc => 'pg_stat_get_subscription' },
 { oid => '2026', descr => 'statistics: current backend PID',
   proname => 'pg_backend_pid', provolatile => 's', proparallel => 'r',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 9dd137415e..c69f6e471b 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2086,6 +2086,7 @@ pg_stat_ssl| SELECT s.pid,
 pg_stat_subscription| SELECT su.oid AS subid,
     su.subname,
     st.pid,
+    st.apply_leader_pid,
     st.relid,
     st.received_lsn,
     st.last_msg_send_time,
@@ -2093,7 +2094,7 @@ pg_stat_subscription| SELECT su.oid AS subid,
     st.latest_end_lsn,
     st.latest_end_time
    FROM (pg_subscription su
-     LEFT JOIN pg_stat_get_subscription(NULL::oid) st(subid, relid, pid, received_lsn, last_msg_send_time, last_msg_receipt_time, latest_end_lsn, latest_end_time) ON ((st.subid = su.oid)));
+     LEFT JOIN pg_stat_get_subscription(NULL::oid) st(subid, relid, pid, apply_leader_pid, received_lsn, last_msg_send_time, last_msg_receipt_time, latest_end_lsn, latest_end_time) ON ((st.subid = su.oid)));
 pg_stat_subscription_stats| SELECT ss.subid,
     s.subname,
     ss.apply_error_count,
-- 
2.23.0.windows.1



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  To: [email protected]
  Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
  Subject: RE: Perform streaming logical transactions by background workers and parallel apply
  In-Reply-To: <OS3PR01MB6275F145878B4A44586C46CE9E499@OS3PR01MB6275.jpnprd01.prod.outlook.com>

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