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From: Tomas Vondra <[email protected]>
To: Hannu Krosing <[email protected]>
Cc: Peter Eisentraut <[email protected]>
Cc: vignesh C <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: Petr Jelinek <[email protected]>
Subject: Re: logical decoding and replication of sequences
Date: Fri, 19 Nov 2021 20:54:46 +0100
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<CALDaNm3gZZjBKWs7gufQep9ikJMtoY9Xv4CsYTpYRaT720RpbQ@mail.gmail.com>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>
	<CAMT0RQQeDR51xs8zTa25YpfKB1B34nS-Q4hhsRPznVsjMB_P1w@mail.gmail.com>
	<[email protected]>

Hi,

I've spent a bit of time exploring the alternative approach outlined by 
Hannu, i.e. tracking sequences accessed by the transaction, and logging 
the final state just once at COMMIT. Attached is an experimental version 
of the patch series doing that - 0001 does the original approach 
(decoding the sequence updates from WAL) and then 0002 reworks it to 
this alternative solution. The 0003 and 0004 stay mostly the same, 
except for minor fixes. Some of the tests in 0003/0004 fail, because 
0002 changes the semantics in various ways (more about that later).

The original approach (0001) may seem complex at first, but in principle 
it just  decodes changes to the sequence relation, and either stashes 
them into transaction (just like other changes) or applies them right 
away. I'd say that's the most complicated part - deciding whether the 
change is transactional or not.

0002 reworks that so that it doesn't decode the existing WAL records, 
but tracks sequences which have been modified (updated on-disk state) 
and then accessed in the current transaction. And then at COMMIT time we 
write a new WAL message with info about the sequence.

I realized we already cache sequences for each session - seqhashtab in 
sequence.c. It doesn't have any concept of a transaction, but it seems 
fairly easy to make that possible. I did this by adding two flags

  - needs_log - means the seesion advanced the sequence (on disk)
  - touched   - true if the current xact called nextval() etc.

The idea is that what matters is updates to on-disk state, so whenever 
we do that we set needs_log. But it only matters when the changes are 
made visible in a committed transaction. Consider for example this:

BEGIN;
SELECT nextval('s') FROM generate_series(1,10000) s(i);
ROLLBACK;
SELECT nextval('s');

The first nextval() call certainly sets both flags to true, at least for 
default sequences caching 32 values. But the values are not confirmed to 
the user because of the rollback - this resets 'touched' flag, but 
leaves 'needs_log' set to true.

And then the next nextval() - which may easily be just from cache - sets 
touched=true again, and logs the sequence state at (implicit) commit. 
Which resets both flags again.

The logging/cleanup happens in AtEOXact_Sequences() which gets called 
before commit/abort. This walks all cached sequences and writes the 
state for those with both flags true (or resets flag for abort).

The cache also keeps info about the last "sequence state" in the 
session, which is then used when writing into into WAL.


To write the sequence state into WAL, I've added a new WAL record 
xl_logical_sequence to RM_LOGICALMSG_ID, next to the xl_logical_message. 
It's a bit arbitrary, maybe it should be part of RM_SEQ_ID, but it does 
the trick. I don't think this is the main issue and it's easy enough to 
move it elsewhere if needed.

So, that seems fairly straight-forward and it may reduce the number of 
replication messages for large transactions. Unfortunately, it's not 
much simpler compared to the first approach - the amount of code is 
about the same, and there's a bunch of other issues.

The main issue seems to be about ordering. Consider multiple sessions 
all advancing the sequence. With the "old" approach this was naturally 
ordered - the order in which the increments were written to WAL made 
sense. But the sessions may advance the sequences in one order and then 
commit in a different order, which mixes the updates. Consider for 
example this scenario with two concurrent transactions:

T1: nextval('s') -> allocates values [1,32]
T2: nextval('s') -> allocates values [33,64]
T2: commit -> logs [33,64]
T1: commit -> logs [1,32]

The result is the sequence on the replica diverted because it replayed 
the increments in the opposite order.

I can think of two ways to fix this. Firstly, we could "merge" the 
increments in some smart way, e.g. by discarding values considered 
"stale" (like decrements). But that seems pretty fragile, because the 
sequence may be altered in various ways, reset, etc. And it seems more 
like transferring responsibility to someone else instead of actually 
solving the issue.

The other fix is simply reading the current sequence state from disk at 
commit and logging that (instead of the values cached from the last 
increment). But I'm rather skeptical about doing such things right 
before COMMIT.



regards

-- 
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Attachments:

  [text/x-patch] 0004-Add-support-for-decoding-sequences-to-built-20211118.patch (77.1K, ../[email protected]/2-0004-Add-support-for-decoding-sequences-to-built-20211118.patch)
  download | inline diff:
From 24c30875c9b024b830a03b780fedbcd130395c25 Mon Sep 17 00:00:00 2001
From: Tomas Vondra <[email protected]>
Date: Fri, 19 Nov 2021 01:12:23 +0100
Subject: [PATCH 4/4] Add support for decoding sequences to built-in
 replication

---
 doc/src/sgml/catalogs.sgml                  |  71 ++++
 doc/src/sgml/ref/alter_publication.sgml     |  24 +-
 doc/src/sgml/ref/alter_subscription.sgml    |   4 +-
 src/backend/catalog/pg_publication.c        | 149 ++++++++-
 src/backend/catalog/system_views.sql        |  10 +
 src/backend/commands/publicationcmds.c      | 350 +++++++++++++++++++-
 src/backend/commands/sequence.c             |  79 +++++
 src/backend/commands/subscriptioncmds.c     | 272 +++++++++++++++
 src/backend/executor/execReplication.c      |   2 +-
 src/backend/nodes/copyfuncs.c               |   1 +
 src/backend/nodes/equalfuncs.c              |   1 +
 src/backend/parser/gram.y                   |  32 ++
 src/backend/replication/logical/proto.c     |  54 +++
 src/backend/replication/logical/tablesync.c | 118 ++++++-
 src/backend/replication/logical/worker.c    |  60 ++++
 src/backend/replication/pgoutput/pgoutput.c |  86 ++++-
 src/backend/utils/cache/relcache.c          |   4 +-
 src/bin/psql/tab-complete.c                 |   6 +-
 src/include/catalog/pg_proc.dat             |   5 +
 src/include/catalog/pg_publication.h        |  14 +
 src/include/commands/sequence.h             |   1 +
 src/include/nodes/parsenodes.h              |   6 +
 src/include/replication/logicalproto.h      |  20 ++
 src/include/replication/pgoutput.h          |   1 +
 src/test/regress/expected/rules.out         |   8 +
 src/test/subscription/t/023_sequences.pl    | 196 +++++++++++
 26 files changed, 1542 insertions(+), 32 deletions(-)
 create mode 100644 src/test/subscription/t/023_sequences.pl

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index c1d11be73f..37b9b52b29 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -9498,6 +9498,11 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       <entry>prepared transactions</entry>
      </row>
 
+     <row>
+      <entry><link linkend="view-pg-publication-sequences"><structname>pg_publication_sequences</structname></link></entry>
+      <entry>publications and their associated sequences</entry>
+     </row>
+
      <row>
       <entry><link linkend="view-pg-publication-tables"><structname>pg_publication_tables</structname></link></entry>
       <entry>publications and their associated tables</entry>
@@ -11333,6 +11338,72 @@ SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
 
  </sect1>
 
+ <sect1 id="view-pg-publication-sequences">
+  <title><structname>pg_publication_sequences</structname></title>
+
+  <indexterm zone="view-pg-publication-sequences">
+   <primary>pg_publication_sequences</primary>
+  </indexterm>
+
+  <para>
+   The view <structname>pg_publication_sequences</structname> provides
+   information about the mapping between publications and the sequences they
+   contain.  Unlike the underlying catalog
+   <link linkend="catalog-pg-publication-rel"><structname>pg_publication_rel</structname></link>,
+   this view expands
+   publications defined as <literal>FOR ALL SEQUENCES</literal>, so for such
+   publications there will be a row for each eligible sequence.
+  </para>
+
+  <table>
+   <title><structname>pg_publication_sequences</structname> Columns</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>pubname</structfield> <type>name</type>
+       (references <link linkend="catalog-pg-publication"><structname>pg_publication</structname></link>.<structfield>pubname</structfield>)
+      </para>
+      <para>
+       Name of publication
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>schemaname</structfield> <type>name</type>
+       (references <link linkend="catalog-pg-namespace"><structname>pg_namespace</structname></link>.<structfield>nspname</structfield>)
+      </para>
+      <para>
+       Name of schema containing sequence
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>sequencename</structfield> <type>name</type>
+       (references <link linkend="catalog-pg-class"><structname>pg_class</structname></link>.<structfield>relname</structfield>)
+      </para>
+      <para>
+       Name of sequence
+      </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+ </sect1>
+
  <sect1 id="view-pg-publication-tables">
   <title><structname>pg_publication_tables</structname></title>
 
diff --git a/doc/src/sgml/ref/alter_publication.sgml b/doc/src/sgml/ref/alter_publication.sgml
index bb4ef5e5e2..4d166ad3f9 100644
--- a/doc/src/sgml/ref/alter_publication.sgml
+++ b/doc/src/sgml/ref/alter_publication.sgml
@@ -31,7 +31,9 @@ ALTER PUBLICATION <replaceable class="parameter">name</replaceable> RENAME TO <r
 <phrase>where <replaceable class="parameter">publication_object</replaceable> is one of:</phrase>
 
     TABLE [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ * ] [, ... ]
+    SEQUENCE <replaceable class="parameter">sequence_name</replaceable> [ * ] [, ... ]
     ALL TABLES IN SCHEMA { <replaceable class="parameter">schema_name</replaceable> | CURRENT_SCHEMA } [, ... ]
+    ALL SEQUENCE IN SCHEMA { <replaceable class="parameter">schema_name</replaceable> | CURRENT_SCHEMA } [, ... ]
 </synopsis>
  </refsynopsisdiv>
 
@@ -56,7 +58,18 @@ ALTER PUBLICATION <replaceable class="parameter">name</replaceable> RENAME TO <r
   </para>
 
   <para>
-   The fourth variant of this command listed in the synopsis can change
+   The next three variants change which sequences are part of the publication.
+   The <literal>SET SEQUENCE</literal> clause will replace the list of sequences
+   in the publication with the specified one.  The <literal>ADD SEQUENCE</literal>
+   and <literal>DROP SEQUENCE</literal> clauses will add and remove one or more
+   sequences from the publication.  Note that adding sequences to a publication
+   that is already subscribed to will require a <literal>ALTER SUBSCRIPTION
+   ... REFRESH PUBLICATION</literal> action on the subscribing side in order
+   to become effective.
+  </para>
+
+  <para>
+   The seventh variant of this command listed in the synopsis can change
    all of the publication properties specified in
    <xref linkend="sql-createpublication"/>.  Properties not mentioned in the
    command retain their previous settings.
@@ -123,6 +136,15 @@ ALTER PUBLICATION <replaceable class="parameter">name</replaceable> RENAME TO <r
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><replaceable class="parameter">sequence_name</replaceable></term>
+    <listitem>
+     <para>
+      Name of an existing sequence.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><literal>SET ( <replaceable class="parameter">publication_parameter</replaceable> [= <replaceable class="parameter">value</replaceable>] [, ... ] )</literal></term>
     <listitem>
diff --git a/doc/src/sgml/ref/alter_subscription.sgml b/doc/src/sgml/ref/alter_subscription.sgml
index 0b027cc346..8f28cf03f4 100644
--- a/doc/src/sgml/ref/alter_subscription.sgml
+++ b/doc/src/sgml/ref/alter_subscription.sgml
@@ -147,7 +147,7 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
     <listitem>
      <para>
       Fetch missing table information from publisher.  This will start
-      replication of tables that were added to the subscribed-to publications
+      replication of tables and sequences that were added to the subscribed-to publications
       since <command>CREATE SUBSCRIPTION</command> or
       the last invocation of <command>REFRESH PUBLICATION</command>.
      </para>
@@ -164,7 +164,7 @@ ALTER SUBSCRIPTION <replaceable class="parameter">name</replaceable> RENAME TO <
           Specifies whether to copy pre-existing data in the publications
           that are being subscribed to when the replication starts.
           The default is <literal>true</literal>.  (Previously-subscribed
-          tables are not copied.)
+          tables and sequences are not copied.)
          </para>
         </listitem>
        </varlistentry>
diff --git a/src/backend/catalog/pg_publication.c b/src/backend/catalog/pg_publication.c
index 63579b2f82..2d5bc73a96 100644
--- a/src/backend/catalog/pg_publication.c
+++ b/src/backend/catalog/pg_publication.c
@@ -54,7 +54,8 @@ check_publication_add_relation(Relation targetrel)
 {
 	/* Must be a regular or partitioned table */
 	if (RelationGetForm(targetrel)->relkind != RELKIND_RELATION &&
-		RelationGetForm(targetrel)->relkind != RELKIND_PARTITIONED_TABLE)
+		RelationGetForm(targetrel)->relkind != RELKIND_PARTITIONED_TABLE &&
+		RelationGetForm(targetrel)->relkind != RELKIND_SEQUENCE)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("cannot add relation \"%s\" to publication",
@@ -131,7 +132,8 @@ static bool
 is_publishable_class(Oid relid, Form_pg_class reltuple)
 {
 	return (reltuple->relkind == RELKIND_RELATION ||
-			reltuple->relkind == RELKIND_PARTITIONED_TABLE) &&
+			reltuple->relkind == RELKIND_PARTITIONED_TABLE ||
+			reltuple->relkind == RELKIND_SEQUENCE) &&
 		!IsCatalogRelationOid(relid) &&
 		reltuple->relpersistence == RELPERSISTENCE_PERMANENT &&
 		relid >= FirstNormalObjectId;
@@ -480,6 +482,11 @@ GetPublicationRelations(Oid pubid, PublicationPartOpt pub_partopt)
 		Form_pg_publication_rel pubrel;
 
 		pubrel = (Form_pg_publication_rel) GETSTRUCT(tup);
+
+		/* skip sequences here */
+		if (get_rel_relkind(pubrel->prrelid) == RELKIND_SEQUENCE)
+			continue;
+
 		result = GetPubPartitionOptionRelations(result, pub_partopt,
 												pubrel->prrelid);
 	}
@@ -490,6 +497,49 @@ GetPublicationRelations(Oid pubid, PublicationPartOpt pub_partopt)
 	return result;
 }
 
+/*
+ * Gets list of relation oids for a publication (sequences only).
+ *
+ * This should only be used for normal publications, the FOR ALL TABLES
+ * should use GetAllSequencesPublicationRelations().
+ */
+List *
+GetPublicationSequenceRelations(Oid pubid)
+{
+	List	   *result;
+	Relation	pubrelsrel;
+	ScanKeyData scankey;
+	SysScanDesc scan;
+	HeapTuple	tup;
+
+	/* Find all publications associated with the relation. */
+	pubrelsrel = table_open(PublicationRelRelationId, AccessShareLock);
+
+	ScanKeyInit(&scankey,
+				Anum_pg_publication_rel_prpubid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(pubid));
+
+	scan = systable_beginscan(pubrelsrel, PublicationRelPrrelidPrpubidIndexId,
+							  true, NULL, 1, &scankey);
+
+	result = NIL;
+	while (HeapTupleIsValid(tup = systable_getnext(scan)))
+	{
+		Form_pg_publication_rel pubrel;
+
+		pubrel = (Form_pg_publication_rel) GETSTRUCT(tup);
+
+		if (get_rel_relkind(pubrel->prrelid) == RELKIND_SEQUENCE)
+			result = lappend_oid(result, pubrel->prrelid);
+	}
+
+	systable_endscan(scan);
+	table_close(pubrelsrel, AccessShareLock);
+
+	return result;
+}
+
 /*
  * Gets list of publication oids for publications marked as FOR ALL TABLES.
  */
@@ -735,6 +785,46 @@ GetAllSchemaPublicationRelations(Oid pubid, PublicationPartOpt pub_partopt)
 	return result;
 }
 
+/*
+ * Gets list of all relation published by FOR ALL TABLES publication(s).
+ *
+ * If the publication publishes partition changes via their respective root
+ * partitioned tables, we must exclude partitions in favor of including the
+ * root partitioned tables.
+ */
+List *
+GetAllSequencesPublicationRelations(void)
+{
+	Relation	classRel;
+	ScanKeyData key[1];
+	TableScanDesc scan;
+	HeapTuple	tuple;
+	List	   *result = NIL;
+
+	classRel = table_open(RelationRelationId, AccessShareLock);
+
+	ScanKeyInit(&key[0],
+				Anum_pg_class_relkind,
+				BTEqualStrategyNumber, F_CHAREQ,
+				CharGetDatum(RELKIND_SEQUENCE));
+
+	scan = table_beginscan_catalog(classRel, 1, key);
+
+	while ((tuple = heap_getnext(scan, ForwardScanDirection)) != NULL)
+	{
+		Form_pg_class relForm = (Form_pg_class) GETSTRUCT(tuple);
+		Oid			relid = relForm->oid;
+
+		if (is_publishable_class(relid, relForm))
+			result = lappend_oid(result, relid);
+	}
+
+	table_endscan(scan);
+
+	table_close(classRel, AccessShareLock);
+	return result;
+}
+
 /*
  * Get publication using oid
  *
@@ -757,10 +847,12 @@ GetPublication(Oid pubid)
 	pub->oid = pubid;
 	pub->name = pstrdup(NameStr(pubform->pubname));
 	pub->alltables = pubform->puballtables;
+	pub->allsequences = pubform->puballsequences;
 	pub->pubactions.pubinsert = pubform->pubinsert;
 	pub->pubactions.pubupdate = pubform->pubupdate;
 	pub->pubactions.pubdelete = pubform->pubdelete;
 	pub->pubactions.pubtruncate = pubform->pubtruncate;
+	pub->pubactions.pubsequence = pubform->pubsequence;
 	pub->pubviaroot = pubform->pubviaroot;
 
 	ReleaseSysCache(tup);
@@ -915,3 +1007,56 @@ pg_get_publication_tables(PG_FUNCTION_ARGS)
 
 	SRF_RETURN_DONE(funcctx);
 }
+
+/*
+ * Returns Oids of sequences in a publication.
+ */
+Datum
+pg_get_publication_sequences(PG_FUNCTION_ARGS)
+{
+	FuncCallContext *funcctx;
+	char	   *pubname = text_to_cstring(PG_GETARG_TEXT_PP(0));
+	Publication *publication;
+	List	   *sequences;
+
+	/* stuff done only on the first call of the function */
+	if (SRF_IS_FIRSTCALL())
+	{
+		MemoryContext oldcontext;
+
+		/* create a function context for cross-call persistence */
+		funcctx = SRF_FIRSTCALL_INIT();
+
+		/* switch to memory context appropriate for multiple function calls */
+		oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);
+
+		publication = GetPublicationByName(pubname, false);
+
+		/*
+		 * Publications support partitioned tables, although all changes are
+		 * replicated using leaf partition identity and schema, so we only
+		 * need those.
+		 */
+		if (publication->allsequences)
+			sequences = GetAllSequencesPublicationRelations();
+		else
+			sequences = GetPublicationSequenceRelations(publication->oid);
+
+		funcctx->user_fctx = (void *) sequences;
+
+		MemoryContextSwitchTo(oldcontext);
+	}
+
+	/* stuff done on every call of the function */
+	funcctx = SRF_PERCALL_SETUP();
+	sequences = (List *) funcctx->user_fctx;
+
+	if (funcctx->call_cntr < list_length(sequences))
+	{
+		Oid			relid = list_nth_oid(sequences, funcctx->call_cntr);
+
+		SRF_RETURN_NEXT(funcctx, ObjectIdGetDatum(relid));
+	}
+
+	SRF_RETURN_DONE(funcctx);
+}
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index eb560955cd..2c12d373c1 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -372,6 +372,16 @@ CREATE VIEW pg_publication_tables AS
          pg_class C JOIN pg_namespace N ON (N.oid = C.relnamespace)
     WHERE C.oid = GPT.relid;
 
+CREATE VIEW pg_publication_sequences AS
+    SELECT
+        P.pubname AS pubname,
+        N.nspname AS schemaname,
+        C.relname AS sequencename
+    FROM pg_publication P,
+         LATERAL pg_get_publication_sequences(P.pubname) GPT,
+         pg_class C JOIN pg_namespace N ON (N.oid = C.relnamespace)
+    WHERE C.oid = GPT.relid;
+
 CREATE VIEW pg_locks AS
     SELECT * FROM pg_lock_status() AS L;
 
diff --git a/src/backend/commands/publicationcmds.c b/src/backend/commands/publicationcmds.c
index 7d4a0e95f6..e8dfb1a068 100644
--- a/src/backend/commands/publicationcmds.c
+++ b/src/backend/commands/publicationcmds.c
@@ -16,6 +16,7 @@
 
 #include "access/genam.h"
 #include "access/htup_details.h"
+#include "access/relation.h"
 #include "access/table.h"
 #include "access/xact.h"
 #include "catalog/catalog.h"
@@ -59,6 +60,12 @@ static void PublicationAddSchemas(Oid pubid, List *schemas, bool if_not_exists,
 								  AlterPublicationStmt *stmt);
 static void PublicationDropSchemas(Oid pubid, List *schemas, bool missing_ok);
 
+static List *OpenSequenceList(List *sequences);
+static void CloseSequenceList(List *rels);
+static void PublicationAddSequences(Oid pubid, List *rels, bool if_not_exists,
+								 AlterPublicationStmt *stmt);
+static void PublicationDropSequences(Oid pubid, List *rels, bool missing_ok);
+
 static void
 parse_publication_options(ParseState *pstate,
 						  List *options,
@@ -77,6 +84,7 @@ parse_publication_options(ParseState *pstate,
 	pubactions->pubupdate = true;
 	pubactions->pubdelete = true;
 	pubactions->pubtruncate = true;
+	pubactions->pubsequence = true;
 	*publish_via_partition_root = false;
 
 	/* Parse options */
@@ -101,6 +109,7 @@ parse_publication_options(ParseState *pstate,
 			pubactions->pubupdate = false;
 			pubactions->pubdelete = false;
 			pubactions->pubtruncate = false;
+			pubactions->pubsequence = false;
 
 			*publish_given = true;
 			publish = defGetString(defel);
@@ -123,6 +132,8 @@ parse_publication_options(ParseState *pstate,
 					pubactions->pubdelete = true;
 				else if (strcmp(publish_opt, "truncate") == 0)
 					pubactions->pubtruncate = true;
+				else if (strcmp(publish_opt, "sequence") == 0)
+					pubactions->pubsequence = true;
 				else
 					ereport(ERROR,
 							(errcode(ERRCODE_SYNTAX_ERROR),
@@ -149,7 +160,9 @@ parse_publication_options(ParseState *pstate,
  */
 static void
 ObjectsInPublicationToOids(List *pubobjspec_list, ParseState *pstate,
-						   List **rels, List **schemas)
+						   List **tables, List **sequences,
+						   List **tables_schemas, List **sequences_schemas,
+						   List **schemas)
 {
 	ListCell   *cell;
 	PublicationObjSpec *pubobj;
@@ -167,12 +180,23 @@ ObjectsInPublicationToOids(List *pubobjspec_list, ParseState *pstate,
 		switch (pubobj->pubobjtype)
 		{
 			case PUBLICATIONOBJ_TABLE:
-				*rels = lappend(*rels, pubobj->pubtable);
+				*tables = lappend(*tables, pubobj->pubtable);
+				break;
+			case PUBLICATIONOBJ_SEQUENCE:
+				*sequences = lappend(*sequences, pubobj->pubtable);
 				break;
 			case PUBLICATIONOBJ_TABLE_IN_SCHEMA:
 				schemaid = get_namespace_oid(pubobj->name, false);
 
 				/* Filter out duplicates if user specifies "sch1, sch1" */
+				*tables_schemas = list_append_unique_oid(*tables_schemas, schemaid);
+				*schemas = list_append_unique_oid(*schemas, schemaid);
+				break;
+			case PUBLICATIONOBJ_SEQUENCE_IN_SCHEMA:
+				schemaid = get_namespace_oid(pubobj->name, false);
+
+				/* Filter out duplicates if user specifies "sch1, sch1" */
+				*sequences_schemas = list_append_unique_oid(*sequences_schemas, schemaid);
 				*schemas = list_append_unique_oid(*schemas, schemaid);
 				break;
 			case PUBLICATIONOBJ_TABLE_IN_CUR_SCHEMA:
@@ -186,6 +210,21 @@ ObjectsInPublicationToOids(List *pubobjspec_list, ParseState *pstate,
 				list_free(search_path);
 
 				/* Filter out duplicates if user specifies "sch1, sch1" */
+				*tables_schemas = list_append_unique_oid(*tables_schemas, schemaid);
+				*schemas = list_append_unique_oid(*schemas, schemaid);
+				break;
+			case PUBLICATIONOBJ_SEQUENCE_IN_CUR_SCHEMA:
+				search_path = fetch_search_path(false);
+				if (search_path == NIL) /* nothing valid in search_path? */
+					ereport(ERROR,
+							errcode(ERRCODE_UNDEFINED_SCHEMA),
+							errmsg("no schema has been selected for CURRENT_SCHEMA"));
+
+				schemaid = linitial_oid(search_path);
+				list_free(search_path);
+
+				/* Filter out duplicates if user specifies "sch1, sch1" */
+				*sequences_schemas = list_append_unique_oid(*sequences_schemas, schemaid);
 				*schemas = list_append_unique_oid(*schemas, schemaid);
 				break;
 			default:
@@ -251,7 +290,10 @@ CreatePublication(ParseState *pstate, CreatePublicationStmt *stmt)
 	bool		publish_via_partition_root_given;
 	bool		publish_via_partition_root;
 	AclResult	aclresult;
-	List	   *relations = NIL;
+	List	   *tables = NIL;
+	List	   *sequences = NIL;
+	List	   *tables_schemaidlist = NIL;
+	List	   *sequences_schemaidlist = NIL;
 	List	   *schemaidlist = NIL;
 
 	/* must have CREATE privilege on database */
@@ -306,6 +348,8 @@ CreatePublication(ParseState *pstate, CreatePublicationStmt *stmt)
 		BoolGetDatum(pubactions.pubdelete);
 	values[Anum_pg_publication_pubtruncate - 1] =
 		BoolGetDatum(pubactions.pubtruncate);
+	values[Anum_pg_publication_pubsequence - 1] =
+		BoolGetDatum(pubactions.pubsequence);
 	values[Anum_pg_publication_pubviaroot - 1] =
 		BoolGetDatum(publish_via_partition_root);
 
@@ -330,26 +374,40 @@ CreatePublication(ParseState *pstate, CreatePublicationStmt *stmt)
 	}
 	else
 	{
-		ObjectsInPublicationToOids(stmt->pubobjects, pstate, &relations,
+		ObjectsInPublicationToOids(stmt->pubobjects, pstate,
+								   &tables, &sequences,
+								   &tables_schemaidlist,
+								   &sequences_schemaidlist,
 								   &schemaidlist);
 
 		/* FOR ALL TABLES IN SCHEMA requires superuser */
-		if (list_length(schemaidlist) > 0 && !superuser())
+		if (list_length(tables_schemaidlist) > 0 && !superuser())
 			ereport(ERROR,
 					errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 					errmsg("must be superuser to create FOR ALL TABLES IN SCHEMA publication"));
 
-		if (list_length(relations) > 0)
+		if (list_length(tables) > 0)
 		{
 			List	   *rels;
 
-			rels = OpenTableList(relations);
-			CheckObjSchemaNotAlreadyInPublication(rels, schemaidlist,
+			rels = OpenTableList(tables);
+			CheckObjSchemaNotAlreadyInPublication(rels, tables_schemaidlist,
 												  PUBLICATIONOBJ_TABLE);
 			PublicationAddTables(puboid, rels, true, NULL);
 			CloseTableList(rels);
 		}
 
+		if (list_length(sequences) > 0)
+		{
+			List	   *rels;
+
+			rels = OpenSequenceList(sequences);
+			CheckObjSchemaNotAlreadyInPublication(rels, sequences_schemaidlist,
+												  PUBLICATIONOBJ_SEQUENCE);
+			PublicationAddTables(puboid, rels, true, NULL);
+			CloseSequenceList(rels);
+		}
+
 		if (list_length(schemaidlist) > 0)
 		{
 			/*
@@ -651,12 +709,13 @@ AlterPublicationSchemas(AlterPublicationStmt *stmt,
  */
 static void
 CheckAlterPublication(AlterPublicationStmt *stmt, HeapTuple tup,
-					  List *tables, List *schemaidlist)
+					  List *tables, List *tables_schemaidlist,
+					  List *sequences, List *sequences_schemaidlist)
 {
 	Form_pg_publication pubform = (Form_pg_publication) GETSTRUCT(tup);
 
 	if ((stmt->action == DEFELEM_ADD || stmt->action == DEFELEM_SET) &&
-		schemaidlist && !superuser())
+		(tables_schemaidlist || sequences_schemaidlist) && !superuser())
 		ereport(ERROR,
 				(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 				 errmsg("must be superuser to add or set schemas")));
@@ -665,13 +724,24 @@ CheckAlterPublication(AlterPublicationStmt *stmt, HeapTuple tup,
 	 * Check that user is allowed to manipulate the publication tables in
 	 * schema
 	 */
-	if (schemaidlist && pubform->puballtables)
+	if (tables_schemaidlist && pubform->puballtables)
 		ereport(ERROR,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				 errmsg("publication \"%s\" is defined as FOR ALL TABLES",
 						NameStr(pubform->pubname)),
 				 errdetail("Tables from schema cannot be added to, dropped from, or set on FOR ALL TABLES publications.")));
 
+	/*
+	 * Check that user is allowed to manipulate the publication sequences in
+	 * schema
+	 */
+	if (sequences_schemaidlist && pubform->puballsequences)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("publication \"%s\" is defined as FOR ALL SEQUENCES",
+						NameStr(pubform->pubname)),
+				 errdetail("Sequences from schema cannot be added to, dropped from, or set on FOR ALL SEQUENCES publications.")));
+
 	/* Check that user is allowed to manipulate the publication tables. */
 	if (tables && pubform->puballtables)
 		ereport(ERROR,
@@ -679,6 +749,108 @@ CheckAlterPublication(AlterPublicationStmt *stmt, HeapTuple tup,
 				 errmsg("publication \"%s\" is defined as FOR ALL TABLES",
 						NameStr(pubform->pubname)),
 				 errdetail("Tables cannot be added to or dropped from FOR ALL TABLES publications.")));
+
+	/* Check that user is allowed to manipulate the publication tables. */
+	if (sequences && pubform->puballsequences)
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("publication \"%s\" is defined as FOR ALL SEQUENCES",
+						NameStr(pubform->pubname)),
+				 errdetail("Sequences cannot be added to or dropped from FOR ALL SEQUENCES publications.")));
+}
+
+/*
+ * Add or remove sequence to/from publication.
+ */
+static void
+AlterPublicationSequences(AlterPublicationStmt *stmt, HeapTuple tup,
+						  List *sequences, List *schemaidlist)
+{
+	List	   *rels = NIL;
+	Form_pg_publication pubform = (Form_pg_publication) GETSTRUCT(tup);
+	Oid			pubid = pubform->oid;
+
+	/*
+	 * It is quite possible that for the SET case user has not specified any
+	 * tables in which case we need to remove all the existing tables.
+	 */
+	if (!sequences && stmt->action != DEFELEM_SET)
+		return;
+
+	rels = OpenSequenceList(sequences);
+
+	if (stmt->action == DEFELEM_ADD)
+	{
+		List	   *schemas = NIL;
+
+		/*
+		 * Check if the relation is member of the existing schema in the
+		 * publication or member of the schema list specified.
+		 */
+		schemas = list_concat_copy(schemaidlist, GetPublicationSchemas(pubid));
+		CheckObjSchemaNotAlreadyInPublication(rels, schemas,
+											  PUBLICATIONOBJ_SEQUENCE);
+		PublicationAddSequences(pubid, rels, false, stmt);
+	}
+	else if (stmt->action == DEFELEM_DROP)
+		PublicationDropSequences(pubid, rels, false);
+	else						/* DEFELEM_SET */
+	{
+		List	   *oldrelids = GetPublicationRelations(pubid,
+														PUBLICATION_PART_ROOT);
+		List	   *delrels = NIL;
+		ListCell   *oldlc;
+
+		CheckObjSchemaNotAlreadyInPublication(rels, schemaidlist,
+											  PUBLICATIONOBJ_SEQUENCE);
+
+		/* Calculate which relations to drop. */
+		foreach(oldlc, oldrelids)
+		{
+			Oid			oldrelid = lfirst_oid(oldlc);
+			ListCell   *newlc;
+			bool		found = false;
+
+			foreach(newlc, rels)
+			{
+				PublicationRelInfo *newpubrel;
+
+				newpubrel = (PublicationRelInfo *) lfirst(newlc);
+				if (RelationGetRelid(newpubrel->relation) == oldrelid)
+				{
+					found = true;
+					break;
+				}
+			}
+			/* Not yet in the list, open it and add to the list */
+			if (!found)
+			{
+				Relation	oldrel;
+				PublicationRelInfo *pubrel;
+
+				/* Wrap relation into PublicationRelInfo */
+				oldrel = table_open(oldrelid, ShareUpdateExclusiveLock);
+
+				pubrel = palloc(sizeof(PublicationRelInfo));
+				pubrel->relation = oldrel;
+
+				delrels = lappend(delrels, pubrel);
+			}
+		}
+
+		/* And drop them. */
+		PublicationDropSequences(pubid, delrels, true);
+
+		/*
+		 * Don't bother calculating the difference for adding, we'll catch and
+		 * skip existing ones when doing catalog update.
+		 */
+		PublicationAddSequences(pubid, rels, true, stmt);
+
+		CloseSequenceList(delrels);
+	}
+
+	CloseSequenceList(rels);
 }
 
 /*
@@ -716,13 +888,21 @@ AlterPublication(ParseState *pstate, AlterPublicationStmt *stmt)
 		AlterPublicationOptions(pstate, stmt, rel, tup);
 	else
 	{
-		List	   *relations = NIL;
+		List	   *tables = NIL;
+		List	   *sequences = NIL;
+		List	   *tables_schemaidlist = NIL;
+		List	   *sequences_schemaidlist = NIL;
 		List	   *schemaidlist = NIL;
 
-		ObjectsInPublicationToOids(stmt->pubobjects, pstate, &relations,
+		ObjectsInPublicationToOids(stmt->pubobjects, pstate,
+								   &tables, &sequences,
+								   &tables_schemaidlist,
+								   &sequences_schemaidlist,
 								   &schemaidlist);
 
-		CheckAlterPublication(stmt, tup, relations, schemaidlist);
+		CheckAlterPublication(stmt, tup,
+							  tables, tables_schemaidlist,
+							  sequences, sequences_schemaidlist);
 
 		/*
 		 * Lock the publication so nobody else can do anything with it. This
@@ -747,7 +927,9 @@ AlterPublication(ParseState *pstate, AlterPublicationStmt *stmt)
 					errmsg("publication \"%s\" does not exist",
 						   stmt->pubname));
 
-		AlterPublicationTables(stmt, tup, relations, schemaidlist);
+		AlterPublicationTables(stmt, tup, tables, tables_schemaidlist);
+		AlterPublicationSequences(stmt, tup, sequences, sequences_schemaidlist);
+
 		AlterPublicationSchemas(stmt, tup, schemaidlist);
 	}
 
@@ -1155,6 +1337,144 @@ PublicationDropSchemas(Oid pubid, List *schemas, bool missing_ok)
 	}
 }
 
+/*
+ * Open relations specified by a PublicationTable list.
+ * In the returned list of PublicationRelInfo, tables are locked
+ * in ShareUpdateExclusiveLock mode in order to add them to a publication.
+ */
+static List *
+OpenSequenceList(List *sequences)
+{
+	List	   *relids = NIL;
+	List	   *rels = NIL;
+	ListCell   *lc;
+
+	/*
+	 * Open, share-lock, and check all the explicitly-specified relations
+	 */
+	foreach(lc, sequences)
+	{
+		PublicationTable *s = lfirst_node(PublicationTable, lc);
+		Relation	rel;
+		Oid			myrelid;
+		PublicationRelInfo *pub_rel;
+
+		/* Allow query cancel in case this takes a long time */
+		CHECK_FOR_INTERRUPTS();
+
+		rel = table_openrv(s->relation, ShareUpdateExclusiveLock);
+		myrelid = RelationGetRelid(rel);
+
+		/*
+		 * Filter out duplicates if user specifies "foo, foo".
+		 *
+		 * Note that this algorithm is known to not be very efficient (O(N^2))
+		 * but given that it only works on list of tables given to us by user
+		 * it's deemed acceptable.
+		 */
+		if (list_member_oid(relids, myrelid))
+		{
+			table_close(rel, ShareUpdateExclusiveLock);
+			continue;
+		}
+
+		pub_rel = palloc(sizeof(PublicationRelInfo));
+		pub_rel->relation = rel;
+		rels = lappend(rels, pub_rel);
+		relids = lappend_oid(relids, myrelid);
+	}
+
+	list_free(relids);
+
+	return rels;
+}
+
+/*
+ * Close all relations in the list.
+ */
+static void
+CloseSequenceList(List *rels)
+{
+	ListCell   *lc;
+
+	foreach(lc, rels)
+	{
+		PublicationRelInfo *pub_rel;
+
+		pub_rel = (PublicationRelInfo *) lfirst(lc);
+		table_close(pub_rel->relation, NoLock);
+	}
+}
+
+/*
+ * Add listed tables to the publication.
+ */
+static void
+PublicationAddSequences(Oid pubid, List *rels, bool if_not_exists,
+						AlterPublicationStmt *stmt)
+{
+	ListCell   *lc;
+
+	Assert(!stmt || !stmt->for_all_sequences);
+
+	foreach(lc, rels)
+	{
+		PublicationRelInfo *pub_rel = (PublicationRelInfo *) lfirst(lc);
+		Relation	rel = pub_rel->relation;
+		ObjectAddress obj;
+
+		/* Must be owner of the sequence or superuser. */
+		if (!pg_class_ownercheck(RelationGetRelid(rel), GetUserId()))
+			aclcheck_error(ACLCHECK_NOT_OWNER, get_relkind_objtype(rel->rd_rel->relkind),
+						   RelationGetRelationName(rel));
+
+		obj = publication_add_relation(pubid, pub_rel, if_not_exists);
+		if (stmt)
+		{
+			EventTriggerCollectSimpleCommand(obj, InvalidObjectAddress,
+											 (Node *) stmt);
+
+			InvokeObjectPostCreateHook(PublicationRelRelationId,
+									   obj.objectId, 0);
+		}
+	}
+}
+
+/*
+ * Remove listed sequences from the publication.
+ */
+static void
+PublicationDropSequences(Oid pubid, List *rels, bool missing_ok)
+{
+	ObjectAddress obj;
+	ListCell   *lc;
+	Oid			prid;
+
+	foreach(lc, rels)
+	{
+		Relation	rel = (Relation) lfirst(lc);
+		Oid			relid = RelationGetRelid(rel);
+
+		prid = GetSysCacheOid2(PUBLICATIONRELMAP, Anum_pg_publication_rel_oid,
+							   ObjectIdGetDatum(relid),
+							   ObjectIdGetDatum(pubid));
+		if (!OidIsValid(prid))
+		{
+			if (missing_ok)
+				continue;
+
+			ereport(ERROR,
+					(errcode(ERRCODE_UNDEFINED_OBJECT),
+					 errmsg("relation \"%s\" is not part of the publication",
+							RelationGetRelationName(rel))));
+		}
+
+		ObjectAddressSet(obj, PublicationRelRelationId, prid);
+		performDeletion(&obj, DROP_CASCADE, 0);
+	}
+}
+
+
 /*
  * Internal workhorse for changing a publication owner
  */
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index 92d1966f34..b22f83ea82 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -347,6 +347,85 @@ ResetSequence(Oid seq_relid)
 	relation_close(seq_rel, NoLock);
 }
 
+/*
+ * Reset a sequence to its initial value.
+ *
+ * The change is made transactionally, so that on failure of the current
+ * transaction, the sequence will be restored to its previous state.
+ * We do that by creating a whole new relfilenode for the sequence; so this
+ * works much like the rewriting forms of ALTER TABLE.
+ *
+ * Caller is assumed to have acquired AccessExclusiveLock on the sequence,
+ * which must not be released until end of transaction.  Caller is also
+ * responsible for permissions checking.
+ */
+void
+ResetSequence2(Oid seq_relid, int64 last_value, int64 log_cnt, bool is_called)
+{
+	Relation	seq_rel;
+	SeqTable	elm;
+	Form_pg_sequence_data seq;
+	Buffer		buf;
+	HeapTupleData seqdatatuple;
+	HeapTuple	tuple;
+
+	/*
+	 * Read the old sequence.  This does a bit more work than really
+	 * necessary, but it's simple, and we do want to double-check that it's
+	 * indeed a sequence.
+	 */
+	init_sequence(seq_relid, &elm, &seq_rel);
+	(void) read_seq_tuple(seq_rel, &buf, &seqdatatuple);
+
+	/*
+	 * Copy the existing sequence tuple.
+	 */
+	tuple = heap_copytuple(&seqdatatuple);
+
+	/* Now we're done with the old page */
+	UnlockReleaseBuffer(buf);
+
+	/*
+	 * Modify the copied tuple to execute the restart (compare the RESTART
+	 * action in AlterSequence)
+	 */
+	seq = (Form_pg_sequence_data) GETSTRUCT(tuple);
+	seq->last_value = last_value;
+	seq->is_called = is_called;
+	seq->log_cnt = log_cnt;
+
+	/*
+	 * Create a new storage file for the sequence.
+	 */
+	RelationSetNewRelfilenode(seq_rel, seq_rel->rd_rel->relpersistence);
+
+	/*
+	 * Ensure sequence's relfrozenxid is at 0, since it won't contain any
+	 * unfrozen XIDs.  Same with relminmxid, since a sequence will never
+	 * contain multixacts.
+	 */
+	Assert(seq_rel->rd_rel->relfrozenxid == InvalidTransactionId);
+	Assert(seq_rel->rd_rel->relminmxid == InvalidMultiXactId);
+
+	/*
+	 * Insert the modified tuple into the new storage file.
+	 *
+	 * XXX Maybe this should also use created=true, just like the other places
+	 * calling fill_seq_with_data. That's probably needed for correct cascading
+	 * replication.
+	 *
+	 * XXX That'd mean all fill_seq_with_data callers use created=true, making
+	 * the parameter unnecessary.
+	 */
+	fill_seq_with_data(seq_rel, tuple);
+
+	/* Clear local cache so that we don't think we have cached numbers */
+	/* Note that we do not change the currval() state */
+	elm->cached = elm->last;
+
+	relation_close(seq_rel, NoLock);
+}
+
 /*
  * Initialize a sequence's relation with the specified tuple as content
  */
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index c47ba26369..5086526904 100644
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -84,6 +84,7 @@ typedef struct SubOpts
 } SubOpts;
 
 static List *fetch_table_list(WalReceiverConn *wrconn, List *publications);
+static List *fetch_sequence_list(WalReceiverConn *wrconn, List *publications);
 static void check_duplicates_in_publist(List *publist, Datum *datums);
 static List *merge_publications(List *oldpublist, List *newpublist, bool addpub, const char *subname);
 static void ReportSlotConnectionError(List *rstates, Oid subid, char *slotname, char *err);
@@ -502,6 +503,7 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 		char	   *err;
 		WalReceiverConn *wrconn;
 		List	   *tables;
+		List	   *sequences;
 		ListCell   *lc;
 		char		table_state;
 
@@ -540,6 +542,26 @@ CreateSubscription(ParseState *pstate, CreateSubscriptionStmt *stmt,
 										InvalidXLogRecPtr);
 			}
 
+			/*
+			 * Get the sequence list from publisher and build local sequence
+			 * status info.
+			 */
+			sequences = fetch_sequence_list(wrconn, publications);
+			foreach(lc, sequences)
+			{
+				RangeVar   *rv = (RangeVar *) lfirst(lc);
+				Oid			relid;
+
+				relid = RangeVarGetRelid(rv, AccessShareLock, false);
+
+				/* Check for supported relkind. */
+				CheckSubscriptionRelkind(get_rel_relkind(relid),
+										 rv->schemaname, rv->relname);
+
+				AddSubscriptionRelState(subid, relid, table_state,
+										InvalidXLogRecPtr);
+			}
+
 			/*
 			 * If requested, create permanent slot for the subscription. We
 			 * won't use the initial snapshot for anything, so no need to
@@ -712,6 +734,10 @@ AlterSubscription_refresh(Subscription *sub, bool copy_data)
 		{
 			Oid			relid = subrel_local_oids[off];
 
+			/* XXX ignore sequences - maybe do this in GetSubscriptionRelations? */
+			if (get_rel_relkind(relid) == RELKIND_SEQUENCE)
+				continue;
+
 			if (!bsearch(&relid, pubrel_local_oids,
 						 list_length(pubrel_names), sizeof(Oid), oid_cmp))
 			{
@@ -803,6 +829,183 @@ AlterSubscription_refresh(Subscription *sub, bool copy_data)
 				ReplicationSlotDropAtPubNode(wrconn, syncslotname, true);
 			}
 		}
+
+		/*
+		 * XXX now do the same thing for sequences, maybe before the preceding
+		 * block, or earlier?
+		 */
+
+		/* Get the table list from publisher. */
+		pubrel_names = fetch_sequence_list(wrconn, sub->publications);
+
+		/* Get local table list. */
+		subrel_states = GetSubscriptionRelations(sub->oid);
+
+		/*
+		 * Build qsorted array of local table oids for faster lookup. This can
+		 * potentially contain all tables in the database so speed of lookup
+		 * is important.
+		 */
+		subrel_local_oids = palloc(list_length(subrel_states) * sizeof(Oid));
+		off = 0;
+		foreach(lc, subrel_states)
+		{
+			SubscriptionRelState *relstate = (SubscriptionRelState *) lfirst(lc);
+
+			subrel_local_oids[off++] = relstate->relid;
+		}
+		qsort(subrel_local_oids, list_length(subrel_states),
+			  sizeof(Oid), oid_cmp);
+
+		/*
+		 * Rels that we want to remove from subscription and drop any slots
+		 * and origins corresponding to them.
+		 */
+		sub_remove_rels = palloc(list_length(subrel_states) * sizeof(SubRemoveRels));
+
+		/*
+		 * Walk over the remote tables and try to match them to locally known
+		 * tables. If the table is not known locally create a new state for
+		 * it.
+		 *
+		 * Also builds array of local oids of remote tables for the next step.
+		 */
+		off = 0;
+		pubrel_local_oids = palloc(list_length(pubrel_names) * sizeof(Oid));
+
+		foreach(lc, pubrel_names)
+		{
+			RangeVar   *rv = (RangeVar *) lfirst(lc);
+			Oid			relid;
+
+			relid = RangeVarGetRelid(rv, AccessShareLock, false);
+
+			/* Check for supported relkind. */
+			CheckSubscriptionRelkind(get_rel_relkind(relid),
+									 rv->schemaname, rv->relname);
+
+			pubrel_local_oids[off++] = relid;
+
+			if (!bsearch(&relid, subrel_local_oids,
+						 list_length(subrel_states), sizeof(Oid), oid_cmp))
+			{
+				AddSubscriptionRelState(sub->oid, relid,
+										copy_data ? SUBREL_STATE_INIT : SUBREL_STATE_READY,
+										InvalidXLogRecPtr);
+				ereport(DEBUG1,
+						(errmsg_internal("table \"%s.%s\" added to subscription \"%s\"",
+										 rv->schemaname, rv->relname, sub->name)));
+			}
+		}
+
+		/*
+		 * Next remove state for tables we should not care about anymore using
+		 * the data we collected above
+		 */
+		qsort(pubrel_local_oids, list_length(pubrel_names),
+			  sizeof(Oid), oid_cmp);
+
+		remove_rel_len = 0;
+		for (off = 0; off < list_length(subrel_states); off++)
+		{
+			Oid			relid = subrel_local_oids[off];
+
+			/* XXX ignore non-sequences - maybe do this in GetSubscriptionRelations? */
+			if (get_rel_relkind(relid) != RELKIND_SEQUENCE)
+				continue;
+
+			if (!bsearch(&relid, pubrel_local_oids,
+						 list_length(pubrel_names), sizeof(Oid), oid_cmp))
+			{
+				char		state;
+				XLogRecPtr	statelsn;
+
+				/*
+				 * Lock pg_subscription_rel with AccessExclusiveLock to
+				 * prevent any race conditions with the apply worker
+				 * re-launching workers at the same time this code is trying
+				 * to remove those tables.
+				 *
+				 * Even if new worker for this particular rel is restarted it
+				 * won't be able to make any progress as we hold exclusive
+				 * lock on subscription_rel till the transaction end. It will
+				 * simply exit as there is no corresponding rel entry.
+				 *
+				 * This locking also ensures that the state of rels won't
+				 * change till we are done with this refresh operation.
+				 */
+				if (!rel)
+					rel = table_open(SubscriptionRelRelationId, AccessExclusiveLock);
+
+				/* Last known rel state. */
+				state = GetSubscriptionRelState(sub->oid, relid, &statelsn);
+
+				sub_remove_rels[remove_rel_len].relid = relid;
+				sub_remove_rels[remove_rel_len++].state = state;
+
+				RemoveSubscriptionRel(sub->oid, relid);
+
+				logicalrep_worker_stop(sub->oid, relid);
+
+				/*
+				 * For READY state, we would have already dropped the
+				 * tablesync origin.
+				 */
+				if (state != SUBREL_STATE_READY)
+				{
+					char		originname[NAMEDATALEN];
+
+					/*
+					 * Drop the tablesync's origin tracking if exists.
+					 *
+					 * It is possible that the origin is not yet created for
+					 * tablesync worker, this can happen for the states before
+					 * SUBREL_STATE_FINISHEDCOPY. The apply worker can also
+					 * concurrently try to drop the origin and by this time
+					 * the origin might be already removed. For these reasons,
+					 * passing missing_ok = true.
+					 */
+					ReplicationOriginNameForTablesync(sub->oid, relid, originname,
+													  sizeof(originname));
+					replorigin_drop_by_name(originname, true, false);
+				}
+
+				ereport(DEBUG1,
+						(errmsg_internal("table \"%s.%s\" removed from subscription \"%s\"",
+										 get_namespace_name(get_rel_namespace(relid)),
+										 get_rel_name(relid),
+										 sub->name)));
+			}
+		}
+
+		/*
+		 * Drop the tablesync slots associated with removed tables. This has
+		 * to be at the end because otherwise if there is an error while doing
+		 * the database operations we won't be able to rollback dropped slots.
+		 */
+		for (off = 0; off < remove_rel_len; off++)
+		{
+			if (sub_remove_rels[off].state != SUBREL_STATE_READY &&
+				sub_remove_rels[off].state != SUBREL_STATE_SYNCDONE)
+			{
+				char		syncslotname[NAMEDATALEN] = {0};
+
+				/*
+				 * For READY/SYNCDONE states we know the tablesync slot has
+				 * already been dropped by the tablesync worker.
+				 *
+				 * For other states, there is no certainty, maybe the slot
+				 * does not exist yet. Also, if we fail after removing some of
+				 * the slots, next time, it will again try to drop already
+				 * dropped slots and fail. For these reasons, we allow
+				 * missing_ok = true for the drop.
+				 */
+				ReplicationSlotNameForTablesync(sub->oid, sub_remove_rels[off].relid,
+												syncslotname, sizeof(syncslotname));
+				ReplicationSlotDropAtPubNode(wrconn, syncslotname, true);
+			}
+		}
+
 	}
 	PG_FINALLY();
 	{
@@ -1607,6 +1810,75 @@ fetch_table_list(WalReceiverConn *wrconn, List *publications)
 	return tablelist;
 }
 
+/*
+ * Get the list of sequences which belong to specified publications on the
+ * publisher connection.
+ */
+static List *
+fetch_sequence_list(WalReceiverConn *wrconn, List *publications)
+{
+	WalRcvExecResult *res;
+	StringInfoData cmd;
+	TupleTableSlot *slot;
+	Oid			tableRow[2] = {TEXTOID, TEXTOID};
+	ListCell   *lc;
+	bool		first;
+	List	   *tablelist = NIL;
+
+	Assert(list_length(publications) > 0);
+
+	initStringInfo(&cmd);
+	appendStringInfoString(&cmd, "SELECT DISTINCT s.schemaname, s.sequencename\n"
+						   "  FROM pg_catalog.pg_publication_sequences s\n"
+						   " WHERE s.pubname IN (");
+	first = true;
+	foreach(lc, publications)
+	{
+		char	   *pubname = strVal(lfirst(lc));
+
+		if (first)
+			first = false;
+		else
+			appendStringInfoString(&cmd, ", ");
+
+		appendStringInfoString(&cmd, quote_literal_cstr(pubname));
+	}
+	appendStringInfoChar(&cmd, ')');
+
+	res = walrcv_exec(wrconn, cmd.data, 2, tableRow);
+	pfree(cmd.data);
+
+	if (res->status != WALRCV_OK_TUPLES)
+		ereport(ERROR,
+				(errmsg("could not receive list of replicated tables from the publisher: %s",
+						res->err)));
+
+	/* Process tables. */
+	slot = MakeSingleTupleTableSlot(res->tupledesc, &TTSOpsMinimalTuple);
+	while (tuplestore_gettupleslot(res->tuplestore, true, false, slot))
+	{
+		char	   *nspname;
+		char	   *relname;
+		bool		isnull;
+		RangeVar   *rv;
+
+		nspname = TextDatumGetCString(slot_getattr(slot, 1, &isnull));
+		Assert(!isnull);
+		relname = TextDatumGetCString(slot_getattr(slot, 2, &isnull));
+		Assert(!isnull);
+
+		rv = makeRangeVar(nspname, relname, -1);
+		tablelist = lappend(tablelist, rv);
+
+		ExecClearTuple(slot);
+	}
+	ExecDropSingleTupleTableSlot(slot);
+
+	walrcv_clear_result(res);
+
+	return tablelist;
+}
+
 /*
  * This is to report the connection failure while dropping replication slots.
  * Here, we report the WARNING for all tablesync slots so that user can drop
diff --git a/src/backend/executor/execReplication.c b/src/backend/executor/execReplication.c
index 574d7d27fd..6f0d42d551 100644
--- a/src/backend/executor/execReplication.c
+++ b/src/backend/executor/execReplication.c
@@ -608,7 +608,7 @@ void
 CheckSubscriptionRelkind(char relkind, const char *nspname,
 						 const char *relname)
 {
-	if (relkind != RELKIND_RELATION && relkind != RELKIND_PARTITIONED_TABLE)
+	if (relkind != RELKIND_RELATION && relkind != RELKIND_PARTITIONED_TABLE && relkind != RELKIND_SEQUENCE)
 		ereport(ERROR,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 				 errmsg("cannot use relation \"%s.%s\" as logical replication target",
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index ad1ea2ff2f..3dc5eeed91 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -4843,6 +4843,7 @@ _copyCreatePublicationStmt(const CreatePublicationStmt *from)
 	COPY_NODE_FIELD(options);
 	COPY_NODE_FIELD(pubobjects);
 	COPY_SCALAR_FIELD(for_all_tables);
+	COPY_SCALAR_FIELD(for_all_sequences);
 
 	return newnode;
 }
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index f537d3eb96..2317185daf 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2336,6 +2336,7 @@ _equalAlterPublicationStmt(const AlterPublicationStmt *a,
 	COMPARE_NODE_FIELD(options);
 	COMPARE_NODE_FIELD(pubobjects);
 	COMPARE_SCALAR_FIELD(for_all_tables);
+	COMPARE_SCALAR_FIELD(for_all_sequences);
 	COMPARE_SCALAR_FIELD(action);
 
 	return true;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index a6d0cefa6b..5c4e8bf3d7 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -9672,6 +9672,26 @@ PublicationObjSpec:
 					$$->pubobjtype = PUBLICATIONOBJ_TABLE_IN_CUR_SCHEMA;
 					$$->location = @5;
 				}
+			| SEQUENCE relation_expr
+				{
+					$$ = makeNode(PublicationObjSpec);
+					$$->pubobjtype = PUBLICATIONOBJ_SEQUENCE;
+					$$->pubtable = makeNode(PublicationTable);
+					$$->pubtable->relation = $2;
+				}
+			| ALL SEQUENCE IN_P SCHEMA ColId
+				{
+					$$ = makeNode(PublicationObjSpec);
+					$$->pubobjtype = PUBLICATIONOBJ_SEQUENCE_IN_SCHEMA;
+					$$->name = $5;
+					$$->location = @5;
+				}
+			| ALL SEQUENCES IN_P SCHEMA CURRENT_SCHEMA
+				{
+					$$ = makeNode(PublicationObjSpec);
+					$$->pubobjtype = PUBLICATIONOBJ_SEQUENCE_IN_CUR_SCHEMA;
+					$$->location = @5;
+				}
 			| ColId
 				{
 					$$ = makeNode(PublicationObjSpec);
@@ -10007,6 +10027,12 @@ UnlistenStmt:
 				}
 		;
 
+/*
+ * FIXME
+ *
+ * opt_publication_for_sequences and publication_for_sequences should be
+ * copies for sequences
+ */
 
 /*****************************************************************************
  *
@@ -10015,6 +10041,12 @@ UnlistenStmt:
  *		BEGIN / COMMIT / ROLLBACK
  *		(also older versions END / ABORT)
  *
+ * ALTER PUBLICATION name ADD SEQUENCE sequence [, sequence2]
+ *
+ * ALTER PUBLICATION name DROP SEQUENCE sequence [, sequence2]
+ *
+ * ALTER PUBLICATION name SET SEQUENCE sequence [, sequence2]
+ *
  *****************************************************************************/
 
 TransactionStmt:
diff --git a/src/backend/replication/logical/proto.c b/src/backend/replication/logical/proto.c
index 9f5bf4b639..9f53b4c47b 100644
--- a/src/backend/replication/logical/proto.c
+++ b/src/backend/replication/logical/proto.c
@@ -647,6 +647,58 @@ logicalrep_write_message(StringInfo out, TransactionId xid, XLogRecPtr lsn,
 	pq_sendbytes(out, message, sz);
 }
 
+/*
+ * Write SEQUENCE to stream
+ */
+void
+logicalrep_write_sequence(StringInfo out, Relation rel, TransactionId xid,
+						  XLogRecPtr lsn, bool transactional, bool created,
+						  int64 last_value, int64 log_cnt, bool is_called)
+{
+	uint8		flags = 0;
+	char	   *relname;
+
+	pq_sendbyte(out, LOGICAL_REP_MSG_SEQUENCE);
+
+	/* transaction ID (if not valid, we're not streaming) */
+	if (TransactionIdIsValid(xid))
+		pq_sendint32(out, xid);
+
+	pq_sendint8(out, flags);
+	pq_sendint64(out, lsn);
+
+	logicalrep_write_namespace(out, RelationGetNamespace(rel));
+	relname = RelationGetRelationName(rel);
+	pq_sendstring(out, relname);
+
+	pq_sendint8(out, transactional);
+	pq_sendint8(out, created);
+	pq_sendint64(out, last_value);
+	pq_sendint64(out, log_cnt);
+	pq_sendint8(out, is_called);
+}
+
+/*
+ * Read SEQUENCE from the stream.
+ */
+void
+logicalrep_read_sequence(StringInfo in, LogicalRepSequence *seqdata)
+{
+	/* XXX skipping flags and lsn */
+	pq_getmsgint(in, 1);
+	pq_getmsgint64(in);
+
+	/* Read relation name from stream */
+	seqdata->nspname = pstrdup(logicalrep_read_namespace(in));
+	seqdata->seqname = pstrdup(pq_getmsgstring(in));
+
+	seqdata->transactional = pq_getmsgint(in, 1);
+	seqdata->created = pq_getmsgint(in, 1);
+	seqdata->last_value = pq_getmsgint64(in);
+	seqdata->log_cnt = pq_getmsgint64(in);
+	seqdata->is_called = pq_getmsgint(in, 1);
+}
+
 /*
  * Write relation description to the output stream.
  */
@@ -1203,6 +1255,8 @@ logicalrep_message_type(LogicalRepMsgType action)
 			return "STREAM ABORT";
 		case LOGICAL_REP_MSG_STREAM_PREPARE:
 			return "STREAM PREPARE";
+		case LOGICAL_REP_MSG_SEQUENCE:
+			return "SEQUENCE";
 	}
 
 	elog(ERROR, "invalid logical replication message type \"%c\"", action);
diff --git a/src/backend/replication/logical/tablesync.c b/src/backend/replication/logical/tablesync.c
index f07983a43c..24369a1522 100644
--- a/src/backend/replication/logical/tablesync.c
+++ b/src/backend/replication/logical/tablesync.c
@@ -100,6 +100,7 @@
 #include "catalog/pg_subscription_rel.h"
 #include "catalog/pg_type.h"
 #include "commands/copy.h"
+#include "commands/sequence.h"
 #include "miscadmin.h"
 #include "parser/parse_relation.h"
 #include "pgstat.h"
@@ -357,6 +358,12 @@ process_syncing_tables_for_sync(XLogRecPtr current_lsn)
  *
  * If the synchronization position is reached (SYNCDONE), then the table can
  * be marked as READY and is no longer tracked.
+ *
+ * XXX This needs to handle sequences too - after AlterSubscription_refresh
+ * starts caring about sequences, GetSubscriptionNotReadyRelations won't
+ * return just tables, and we'll have to sync them here. Not sure it's worth
+ * creating a new "sync" worker per sequence, maybe we should just sync them
+ * in the current process (it's pretty light-weight).
  */
 static void
 process_syncing_tables_for_apply(XLogRecPtr current_lsn)
@@ -871,6 +878,99 @@ copy_table(Relation rel)
 	logicalrep_rel_close(relmapentry, NoLock);
 }
 
+
+
+/*
+ * FIXME add comment
+ */
+static void
+fetch_sequence_data(char *nspname, char *relname,
+					int64 *last_value, int64 *log_cnt, bool *is_called)
+{
+	WalRcvExecResult *res;
+	StringInfoData cmd;
+	TupleTableSlot *slot;
+	Oid			tableRow[3] = {INT8OID, INT8OID, BOOLOID};
+
+	initStringInfo(&cmd);
+	appendStringInfo(&cmd, "SELECT last_value, log_cnt, is_called\n"
+					   "  FROM %s", quote_qualified_identifier(nspname, relname));
+
+	res = walrcv_exec(LogRepWorkerWalRcvConn, cmd.data, 3, tableRow);
+	pfree(cmd.data);
+
+	if (res->status != WALRCV_OK_TUPLES)
+		ereport(ERROR,
+				(errmsg("could not receive list of replicated tables from the publisher: %s",
+						res->err)));
+
+	/* Process the sequence. */
+	slot = MakeSingleTupleTableSlot(res->tupledesc, &TTSOpsMinimalTuple);
+	while (tuplestore_gettupleslot(res->tuplestore, true, false, slot))
+	{
+		bool		isnull;
+
+		*last_value = DatumGetInt64(slot_getattr(slot, 1, &isnull));
+		Assert(!isnull);
+
+		*log_cnt = DatumGetInt64(slot_getattr(slot, 2, &isnull));
+		Assert(!isnull);
+
+		*is_called = DatumGetBool(slot_getattr(slot, 3, &isnull));
+		Assert(!isnull);
+
+		ExecClearTuple(slot);
+	}
+	ExecDropSingleTupleTableSlot(slot);
+
+	walrcv_clear_result(res);
+}
+
+/*
+ * Copy existing data of a sequence from publisher.
+ *
+ * Caller is responsible for locking the local relation.
+ */
+static void
+copy_sequence(Relation rel)
+{
+	LogicalRepRelMapEntry *relmapentry;
+	LogicalRepRelation lrel;
+	StringInfoData cmd;
+	int64		last_value = 0,
+				log_cnt = 0;
+	bool		is_called = 0;
+
+	/* Get the publisher relation info. */
+	fetch_remote_table_info(get_namespace_name(RelationGetNamespace(rel)),
+							RelationGetRelationName(rel), &lrel);
+
+	/* Put the relation into relmap. */
+	logicalrep_relmap_update(&lrel);
+
+	/* Map the publisher relation to local one. */
+	relmapentry = logicalrep_rel_open(lrel.remoteid, NoLock);
+	Assert(rel == relmapentry->localrel);
+
+	/* Start copy on the publisher. */
+	initStringInfo(&cmd);
+
+	Assert(lrel.relkind == RELKIND_SEQUENCE);
+
+	fetch_sequence_data(lrel.nspname, lrel.relname, &last_value, &log_cnt, &is_called);
+
+	elog(WARNING, "sequence %s info last_value %ld log_cnt %ld is_called %d",
+		 quote_qualified_identifier(lrel.nspname, lrel.relname),
+		 last_value, log_cnt, is_called);
+
+	ResetSequence2(RelationGetRelid(rel), last_value, log_cnt, is_called);
+
+	logicalrep_rel_close(relmapentry, NoLock);
+}
+
+
+
+
 /*
  * Determine the tablesync slot name.
  *
@@ -1106,10 +1206,20 @@ LogicalRepSyncTableStart(XLogRecPtr *origin_startpos)
 						originname)));
 	}
 
-	/* Now do the initial data copy */
-	PushActiveSnapshot(GetTransactionSnapshot());
-	copy_table(rel);
-	PopActiveSnapshot();
+	if (get_rel_relkind(RelationGetRelid(rel)) == RELKIND_SEQUENCE)
+	{
+		/* Now do the initial sequence copy */
+		PushActiveSnapshot(GetTransactionSnapshot());
+		copy_sequence(rel);
+		PopActiveSnapshot();
+	}
+	else
+	{
+		/* Now do the initial data copy */
+		PushActiveSnapshot(GetTransactionSnapshot());
+		copy_table(rel);
+		PopActiveSnapshot();
+	}
 
 	res = walrcv_exec(LogRepWorkerWalRcvConn, "COMMIT", 0, NULL);
 	if (res->status != WALRCV_OK_COMMAND)
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index ae1b391bda..55d48ce5be 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -144,6 +144,7 @@
 #include "catalog/pg_tablespace.h"
 #include "commands/tablecmds.h"
 #include "commands/tablespace.h"
+#include "commands/sequence.h"
 #include "commands/trigger.h"
 #include "executor/executor.h"
 #include "executor/execPartition.h"
@@ -1091,6 +1092,61 @@ apply_handle_origin(StringInfo s)
 				 errmsg_internal("ORIGIN message sent out of order")));
 }
 
+/*
+ * Handle SEQUENCE message.
+ */
+static void
+apply_handle_sequence(StringInfo s)
+{
+	LogicalRepSequence	seq;
+	Oid					relid;
+
+	if (handle_streamed_transaction(LOGICAL_REP_MSG_SEQUENCE, s))
+		return;
+
+	logicalrep_read_sequence(s, &seq);
+
+	/*
+	 * Non-transactional sequence updates should not be part of a remote
+	 * transaction. There should not be any running transaction.
+	 */
+	Assert((!seq.transactional) || in_remote_transaction);
+	Assert(!(!seq.transactional && in_remote_transaction));
+	Assert(!(!seq.transactional && IsTransactionState()));
+
+	/*
+	 * Make sure we're in a transaction (needed by ResetSequence2). For
+	 * non-transactional updates we're guaranteed to start a new one,
+	 * and we'll commit it at the end.
+	 */
+	if (!IsTransactionState())
+	{
+		StartTransactionCommand();
+		maybe_reread_subscription();
+	}
+
+	relid = RangeVarGetRelid(makeRangeVar(seq.nspname,
+										  seq.seqname, -1),
+							 RowExclusiveLock, false);
+
+	/* lock the sequence in AccessExclusiveLock, as expected by ResetSequence2 */
+	elog(WARNING, "locking sequence %d in exclusive mode", relid);
+	LockRelationOid(relid, AccessExclusiveLock);
+
+	elog(WARNING, "applying sequence %s.%s transactional %d created %d last_value %ld log_cnt %ld is_called %d",
+		 seq.nspname, seq.seqname, seq.transactional, seq.created, seq.last_value, seq.log_cnt, seq.is_called);
+
+	/* apply the sequence change */
+	ResetSequence2(relid, seq.last_value, seq.log_cnt, seq.is_called);
+
+	/*
+	 * Commit the per-stream transaction (we only do this when not in
+	 * remote transaction, i.e. for non-transactional sequence updates.
+	 */
+	if (!in_remote_transaction)
+		CommitTransactionCommand();
+}
+
 /*
  * Handle STREAM START message.
  */
@@ -2374,6 +2430,10 @@ apply_dispatch(StringInfo s)
 			 */
 			break;
 
+		case LOGICAL_REP_MSG_SEQUENCE:
+			apply_handle_sequence(s);
+			return;
+
 		case LOGICAL_REP_MSG_STREAM_START:
 			apply_handle_stream_start(s);
 			break;
diff --git a/src/backend/replication/pgoutput/pgoutput.c b/src/backend/replication/pgoutput/pgoutput.c
index 6f6a203dea..fef568b5b2 100644
--- a/src/backend/replication/pgoutput/pgoutput.c
+++ b/src/backend/replication/pgoutput/pgoutput.c
@@ -49,6 +49,10 @@ static void pgoutput_message(LogicalDecodingContext *ctx,
 							 ReorderBufferTXN *txn, XLogRecPtr message_lsn,
 							 bool transactional, const char *prefix,
 							 Size sz, const char *message);
+static void pgoutput_sequence(LogicalDecodingContext *ctx,
+							  ReorderBufferTXN *txn, XLogRecPtr sequence_lsn,
+							  Relation rel, bool transactional, bool created,
+							  int64 last_value, int64 log_cnt, bool is_called);
 static bool pgoutput_origin_filter(LogicalDecodingContext *ctx,
 								   RepOriginId origin_id);
 static void pgoutput_begin_prepare_txn(LogicalDecodingContext *ctx,
@@ -159,6 +163,7 @@ _PG_output_plugin_init(OutputPluginCallbacks *cb)
 	cb->change_cb = pgoutput_change;
 	cb->truncate_cb = pgoutput_truncate;
 	cb->message_cb = pgoutput_message;
+	cb->sequence_cb = pgoutput_sequence;
 	cb->commit_cb = pgoutput_commit_txn;
 
 	cb->begin_prepare_cb = pgoutput_begin_prepare_txn;
@@ -175,6 +180,7 @@ _PG_output_plugin_init(OutputPluginCallbacks *cb)
 	cb->stream_commit_cb = pgoutput_stream_commit;
 	cb->stream_change_cb = pgoutput_change;
 	cb->stream_message_cb = pgoutput_message;
+	cb->stream_sequence_cb = pgoutput_sequence;
 	cb->stream_truncate_cb = pgoutput_truncate;
 	/* transaction streaming - two-phase commit */
 	cb->stream_prepare_cb = pgoutput_stream_prepare_txn;
@@ -188,6 +194,7 @@ parse_output_parameters(List *options, PGOutputData *data)
 	bool		publication_names_given = false;
 	bool		binary_option_given = false;
 	bool		messages_option_given = false;
+	bool		sequences_option_given = false;
 	bool		streaming_given = false;
 	bool		two_phase_option_given = false;
 
@@ -195,6 +202,7 @@ parse_output_parameters(List *options, PGOutputData *data)
 	data->streaming = false;
 	data->messages = false;
 	data->two_phase = false;
+	data->sequences = true;
 
 	foreach(lc, options)
 	{
@@ -260,6 +268,16 @@ parse_output_parameters(List *options, PGOutputData *data)
 
 			data->messages = defGetBoolean(defel);
 		}
+		else if (strcmp(defel->defname, "sequences") == 0)
+		{
+			if (sequences_option_given)
+				ereport(ERROR,
+						(errcode(ERRCODE_SYNTAX_ERROR),
+						 errmsg("conflicting or redundant options")));
+			sequences_option_given = true;
+
+			data->sequences = defGetBoolean(defel);
+		}
 		else if (strcmp(defel->defname, "streaming") == 0)
 		{
 			if (streaming_given)
@@ -856,6 +874,52 @@ pgoutput_message(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 	OutputPluginWrite(ctx, true);
 }
 
+static void
+pgoutput_sequence(LogicalDecodingContext *ctx,
+				  ReorderBufferTXN *txn, XLogRecPtr sequence_lsn,
+				  Relation rel, bool transactional, bool created,
+				  int64 last_value, int64 log_cnt, bool is_called)
+{
+	PGOutputData *data = (PGOutputData *) ctx->output_plugin_private;
+	TransactionId xid = InvalidTransactionId;
+	RelationSyncEntry *relentry;
+
+	if (!data->sequences)
+		return;
+
+	if (!is_publishable_relation(rel))
+		return;
+
+	/*
+	 * Remember the xid for the message in streaming mode. See
+	 * pgoutput_change.
+	 */
+	if (in_streaming)
+		xid = txn->xid;
+
+	relentry = get_rel_sync_entry(data, RelationGetRelid(rel));
+
+	/*
+	 * First check the sequence filter.
+	 *
+	 * We handle just REORDER_BUFFER_CHANGE_SEQUENCE here.
+	 */
+	if (!relentry->pubactions.pubsequence)
+		return;
+
+	OutputPluginPrepareWrite(ctx, true);
+	logicalrep_write_sequence(ctx->out,
+							  rel,
+							  xid,
+							  sequence_lsn,
+							  transactional,
+							  created,
+							  last_value,
+							  log_cnt,
+							  is_called);
+	OutputPluginWrite(ctx, true);
+}
+
 /*
  * Currently we always forward.
  */
@@ -1140,7 +1204,8 @@ get_rel_sync_entry(PGOutputData *data, Oid relid)
 		entry->streamed_txns = NIL;
 		entry->replicate_valid = false;
 		entry->pubactions.pubinsert = entry->pubactions.pubupdate =
-			entry->pubactions.pubdelete = entry->pubactions.pubtruncate = false;
+			entry->pubactions.pubdelete = entry->pubactions.pubtruncate =
+			entry->pubactions.pubsequence = false;
 		entry->publish_as_relid = InvalidOid;
 		entry->map = NULL;		/* will be set by maybe_send_schema() if
 								 * needed */
@@ -1160,6 +1225,7 @@ get_rel_sync_entry(PGOutputData *data, Oid relid)
 		List	   *schemaPubids = GetSchemaPublications(schemaId);
 		ListCell   *lc;
 		Oid			publish_as_relid = relid;
+		bool		is_sequence = (get_rel_relkind(relid) == RELKIND_SEQUENCE);
 
 		/* Reload publications if needed before use. */
 		if (!publications_valid)
@@ -1183,12 +1249,23 @@ get_rel_sync_entry(PGOutputData *data, Oid relid)
 			Publication *pub = lfirst(lc);
 			bool		publish = false;
 
-			if (pub->alltables)
+			if (pub->alltables && (!is_sequence))
 			{
 				publish = true;
 				if (pub->pubviaroot && am_partition)
 					publish_as_relid = llast_oid(get_partition_ancestors(relid));
 			}
+			else if (pub->allsequences && is_sequence)
+			{
+				publish = true;
+			}
+
+			/* if a sequence, just cross-check the list of publications */
+			if (!publish && is_sequence)
+			{
+				if (list_member_oid(pubids, pub->oid))
+					publish = true;
+			}
 
 			if (!publish)
 			{
@@ -1243,10 +1320,12 @@ get_rel_sync_entry(PGOutputData *data, Oid relid)
 				entry->pubactions.pubupdate |= pub->pubactions.pubupdate;
 				entry->pubactions.pubdelete |= pub->pubactions.pubdelete;
 				entry->pubactions.pubtruncate |= pub->pubactions.pubtruncate;
+				entry->pubactions.pubsequence |= pub->pubactions.pubsequence;
 			}
 
 			if (entry->pubactions.pubinsert && entry->pubactions.pubupdate &&
-				entry->pubactions.pubdelete && entry->pubactions.pubtruncate)
+				entry->pubactions.pubdelete && entry->pubactions.pubtruncate &&
+				entry->pubactions.pubsequence)
 				break;
 		}
 
@@ -1391,6 +1470,7 @@ rel_sync_cache_publication_cb(Datum arg, int cacheid, uint32 hashvalue)
 		entry->pubactions.pubupdate = false;
 		entry->pubactions.pubdelete = false;
 		entry->pubactions.pubtruncate = false;
+		entry->pubactions.pubsequence = false;
 	}
 }
 
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index 9fa9e671a1..1c3286a38c 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -5605,6 +5605,7 @@ GetRelationPublicationActions(Relation relation)
 		pubactions->pubupdate |= pubform->pubupdate;
 		pubactions->pubdelete |= pubform->pubdelete;
 		pubactions->pubtruncate |= pubform->pubtruncate;
+		pubactions->pubsequence |= pubform->pubsequence;
 
 		ReleaseSysCache(tup);
 
@@ -5613,7 +5614,8 @@ GetRelationPublicationActions(Relation relation)
 		 * other publications.
 		 */
 		if (pubactions->pubinsert && pubactions->pubupdate &&
-			pubactions->pubdelete && pubactions->pubtruncate)
+			pubactions->pubdelete && pubactions->pubtruncate &&
+			pubactions->pubsequence)
 			break;
 	}
 
diff --git a/src/bin/psql/tab-complete.c b/src/bin/psql/tab-complete.c
index 4f724e4428..59a3502ae2 100644
--- a/src/bin/psql/tab-complete.c
+++ b/src/bin/psql/tab-complete.c
@@ -1647,13 +1647,13 @@ psql_completion(const char *text, int start, int end)
 		COMPLETE_WITH("ADD", "DROP", "OWNER TO", "RENAME TO", "SET");
 	/* ALTER PUBLICATION <name> ADD */
 	else if (Matches("ALTER", "PUBLICATION", MatchAny, "ADD"))
-		COMPLETE_WITH("ALL TABLES IN SCHEMA", "TABLE");
+		COMPLETE_WITH("ALL TABLES IN SCHEMA", "TABLE|SEQUENCE");
 	/* ALTER PUBLICATION <name> DROP */
 	else if (Matches("ALTER", "PUBLICATION", MatchAny, "DROP"))
-		COMPLETE_WITH("ALL TABLES IN SCHEMA", "TABLE");
+		COMPLETE_WITH("ALL TABLES IN SCHEMA", "TABLE|SEQUENCE");
 	/* ALTER PUBLICATION <name> SET */
 	else if (Matches("ALTER", "PUBLICATION", MatchAny, "SET"))
-		COMPLETE_WITH("(", "ALL TABLES IN SCHEMA", "TABLE");
+		COMPLETE_WITH("(", "ALL TABLES IN SCHEMA", "TABLE|SEQUENCE");
 	else if (Matches("ALTER", "PUBLICATION", MatchAny, "ADD|DROP|SET", "ALL", "TABLES", "IN", "SCHEMA"))
 		COMPLETE_WITH_QUERY(Query_for_list_of_schemas
 							" AND nspname != 'pg_catalog' "
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 6412f369f1..be5e3b4d40 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -11513,6 +11513,11 @@
   provolatile => 's', prorettype => 'oid', proargtypes => 'text',
   proallargtypes => '{text,oid}', proargmodes => '{i,o}',
   proargnames => '{pubname,relid}', prosrc => 'pg_get_publication_tables' },
+{ oid => '8000', descr => 'get OIDs of sequences in a publication',
+  proname => 'pg_get_publication_sequences', prorows => '1000', proretset => 't',
+  provolatile => 's', prorettype => 'oid', proargtypes => 'text',
+  proallargtypes => '{text,oid}', proargmodes => '{i,o}',
+  proargnames => '{pubname,relid}', prosrc => 'pg_get_publication_sequences' },
 { oid => '6121',
   descr => 'returns whether a relation can be part of a publication',
   proname => 'pg_relation_is_publishable', provolatile => 's',
diff --git a/src/include/catalog/pg_publication.h b/src/include/catalog/pg_publication.h
index 1ae439e6f3..0a05fb885c 100644
--- a/src/include/catalog/pg_publication.h
+++ b/src/include/catalog/pg_publication.h
@@ -40,6 +40,12 @@ CATALOG(pg_publication,6104,PublicationRelationId)
 	 */
 	bool		puballtables;
 
+	/*
+	 * indicates that this is special publication which should encompass all
+	 * sequences in the database (except for the unlogged and temp ones)
+	 */
+	bool		puballsequences;
+
 	/* true if inserts are published */
 	bool		pubinsert;
 
@@ -52,6 +58,9 @@ CATALOG(pg_publication,6104,PublicationRelationId)
 	/* true if truncates are published */
 	bool		pubtruncate;
 
+	/* true if sequences are published */
+	bool		pubsequence;
+
 	/* true if partition changes are published using root schema */
 	bool		pubviaroot;
 } FormData_pg_publication;
@@ -72,6 +81,7 @@ typedef struct PublicationActions
 	bool		pubupdate;
 	bool		pubdelete;
 	bool		pubtruncate;
+	bool		pubsequence;
 } PublicationActions;
 
 typedef struct Publication
@@ -79,6 +89,7 @@ typedef struct Publication
 	Oid			oid;
 	char	   *name;
 	bool		alltables;
+	bool		allsequences;
 	bool		pubviaroot;
 	PublicationActions pubactions;
 } Publication;
@@ -121,6 +132,9 @@ extern List *GetPubPartitionOptionRelations(List *result,
 											PublicationPartOpt pub_partopt,
 											Oid relid);
 
+extern List *GetAllSequencesPublicationRelations(void);
+extern List *GetPublicationSequenceRelations(Oid pubid);
+
 extern bool is_publishable_relation(Relation rel);
 extern ObjectAddress publication_add_relation(Oid pubid, PublicationRelInfo *targetrel,
 											  bool if_not_exists);
diff --git a/src/include/commands/sequence.h b/src/include/commands/sequence.h
index ddb36b5b17..00038fcea3 100644
--- a/src/include/commands/sequence.h
+++ b/src/include/commands/sequence.h
@@ -60,6 +60,7 @@ extern ObjectAddress DefineSequence(ParseState *pstate, CreateSeqStmt *stmt);
 extern ObjectAddress AlterSequence(ParseState *pstate, AlterSeqStmt *stmt);
 extern void DeleteSequenceTuple(Oid relid);
 extern void ResetSequence(Oid seq_relid);
+extern void ResetSequence2(Oid seq_relid, int64 last_value, int64 log_cnt, bool is_called);
 extern void ResetSequenceCaches(void);
 
 extern void AtEOXact_Sequences(bool isCommit);
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 067138e6b5..44e596fd12 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -3652,6 +3652,10 @@ typedef enum PublicationObjSpecType
 	PUBLICATIONOBJ_TABLE_IN_SCHEMA, /* Tables in schema type */
 	PUBLICATIONOBJ_TABLE_IN_CUR_SCHEMA, /* Get the first element from
 										 * search_path */
+	PUBLICATIONOBJ_SEQUENCE,		/* Sequence type */
+	PUBLICATIONOBJ_SEQUENCE_IN_SCHEMA, /* Sequences in schema type */
+	PUBLICATIONOBJ_SEQUENCE_IN_CUR_SCHEMA, /* Get the first element from
+										 * search_path */
 	PUBLICATIONOBJ_CONTINUATION /* Continuation of previous type */
 } PublicationObjSpecType;
 
@@ -3671,6 +3675,7 @@ typedef struct CreatePublicationStmt
 	List	   *options;		/* List of DefElem nodes */
 	List	   *pubobjects;		/* Optional list of publication objects */
 	bool		for_all_tables; /* Special publication for all tables in db */
+	bool		for_all_sequences; /* Special publication for all sequences in db */
 } CreatePublicationStmt;
 
 typedef struct AlterPublicationStmt
@@ -3687,6 +3692,7 @@ typedef struct AlterPublicationStmt
 	 */
 	List	   *pubobjects;		/* Optional list of publication objects */
 	bool		for_all_tables; /* Special publication for all tables in db */
+	bool		for_all_sequences; /* Special publication for all sequences in db */
 	DefElemAction action;		/* What action to perform with the
 								 * tables/schemas */
 } AlterPublicationStmt;
diff --git a/src/include/replication/logicalproto.h b/src/include/replication/logicalproto.h
index 83741dcf42..d468c3ccfb 100644
--- a/src/include/replication/logicalproto.h
+++ b/src/include/replication/logicalproto.h
@@ -60,6 +60,7 @@ typedef enum LogicalRepMsgType
 	LOGICAL_REP_MSG_RELATION = 'R',
 	LOGICAL_REP_MSG_TYPE = 'Y',
 	LOGICAL_REP_MSG_MESSAGE = 'M',
+	LOGICAL_REP_MSG_SEQUENCE = 'X',	/* FIXME change */
 	LOGICAL_REP_MSG_BEGIN_PREPARE = 'b',
 	LOGICAL_REP_MSG_PREPARE = 'P',
 	LOGICAL_REP_MSG_COMMIT_PREPARED = 'K',
@@ -117,6 +118,19 @@ typedef struct LogicalRepTyp
 	char	   *typname;		/* name of the remote type */
 } LogicalRepTyp;
 
+/* Sequence info */
+typedef struct LogicalRepSequence
+{
+	Oid			remoteid;		/* unique id of the remote sequence */
+	char	   *nspname;		/* schema name of remote sequence */
+	char	   *seqname;		/* name of the remote sequence */
+	bool		transactional;
+	bool		created;
+	int64		last_value;
+	int64		log_cnt;		/* XXX probably not needed? */
+	bool		is_called;		/* XXX probably not needed? */
+} LogicalRepSequence;
+
 /* Transaction info */
 typedef struct LogicalRepBeginData
 {
@@ -227,6 +241,12 @@ extern List *logicalrep_read_truncate(StringInfo in,
 									  bool *cascade, bool *restart_seqs);
 extern void logicalrep_write_message(StringInfo out, TransactionId xid, XLogRecPtr lsn,
 									 bool transactional, const char *prefix, Size sz, const char *message);
+extern void logicalrep_write_sequence(StringInfo out, Relation rel,
+									  TransactionId xid, XLogRecPtr lsn, 
+									  bool transactional, bool created,
+									  int64 last_value, int64 log_cnt,
+									  bool is_called);
+extern void logicalrep_read_sequence(StringInfo in, LogicalRepSequence *seqdata);
 extern void logicalrep_write_rel(StringInfo out, TransactionId xid,
 								 Relation rel);
 extern LogicalRepRelation *logicalrep_read_rel(StringInfo in);
diff --git a/src/include/replication/pgoutput.h b/src/include/replication/pgoutput.h
index 0dc460fb70..97eb2a7ef1 100644
--- a/src/include/replication/pgoutput.h
+++ b/src/include/replication/pgoutput.h
@@ -28,6 +28,7 @@ typedef struct PGOutputData
 	bool		streaming;
 	bool		messages;
 	bool		two_phase;
+	bool		sequences;
 } PGOutputData;
 
 #endif							/* PGOUTPUT_H */
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 2fa00a3c29..b32a1e6729 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1451,6 +1451,14 @@ pg_prepared_xacts| SELECT p.transaction,
    FROM ((pg_prepared_xact() p(transaction, gid, prepared, ownerid, dbid)
      LEFT JOIN pg_authid u ON ((p.ownerid = u.oid)))
      LEFT JOIN pg_database d ON ((p.dbid = d.oid)));
+pg_publication_sequences| SELECT p.pubname,
+    n.nspname AS schemaname,
+    c.relname AS sequencename
+   FROM pg_publication p,
+    LATERAL pg_get_publication_sequences((p.pubname)::text) gpt(relid),
+    (pg_class c
+     JOIN pg_namespace n ON ((n.oid = c.relnamespace)))
+  WHERE (c.oid = gpt.relid);
 pg_publication_tables| SELECT p.pubname,
     n.nspname AS schemaname,
     c.relname AS tablename
diff --git a/src/test/subscription/t/023_sequences.pl b/src/test/subscription/t/023_sequences.pl
new file mode 100644
index 0000000000..c6c438cdbf
--- /dev/null
+++ b/src/test/subscription/t/023_sequences.pl
@@ -0,0 +1,196 @@
+
+# Copyright (c) 2021, PostgreSQL Global Development Group
+
+# This tests that sequences are replicated correctly by logical replication
+use strict;
+use warnings;
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More tests => 6;
+
+# Initialize publisher node
+my $node_publisher = PostgreSQL::Test::Cluster->new('publisher');
+$node_publisher->init(allows_streaming => 'logical');
+$node_publisher->start;
+
+# Create subscriber node
+my $node_subscriber = PostgreSQL::Test::Cluster->new('subscriber');
+$node_subscriber->init(allows_streaming => 'logical');
+$node_subscriber->start;
+
+# Create some preexisting content on publisher
+my $ddl = qq(
+	CREATE SEQUENCE s;
+);
+
+# Setup structure on the publisher
+$node_publisher->safe_psql('postgres', $ddl);
+
+# Create some the same structure on subscriber, and an extra sequence that
+# we'll create on the publisher later
+$ddl = qq(
+	CREATE SEQUENCE s;
+	CREATE SEQUENCE s2;
+);
+
+$node_subscriber->safe_psql('postgres', $ddl);
+
+# Setup logical replication
+my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
+$node_publisher->safe_psql('postgres',
+	"CREATE PUBLICATION seq_pub");
+
+$node_publisher->safe_psql('postgres',
+	"ALTER PUBLICATION seq_pub ADD SEQUENCE s");
+
+$node_subscriber->safe_psql('postgres',
+	"CREATE SUBSCRIPTION seq_sub CONNECTION '$publisher_connstr' PUBLICATION seq_pub WITH (slot_name = seq_sub_slot)"
+);
+
+$node_publisher->wait_for_catchup('seq_sub');
+
+# Wait for initial sync to finish as well
+my $synced_query =
+  "SELECT count(1) = 0 FROM pg_subscription_rel WHERE srsubstate NOT IN ('s', 'r');";
+$node_subscriber->poll_query_until('postgres', $synced_query)
+  or die "Timed out while waiting for subscriber to synchronize data";
+
+# Insert initial test data
+$node_publisher->safe_psql(
+	'postgres', qq(
+	-- generate a number of values using the sequence
+	SELECT nextval('s') FROM generate_series(1,100);
+));
+
+$node_publisher->wait_for_catchup('seq_sub');
+
+# Check the data on subscriber
+my $result = $node_subscriber->safe_psql(
+	'postgres', qq(
+	SELECT * FROM s;
+));
+
+is( $result, '132|0|t',
+	'check replicated sequence values on subscriber');
+
+
+# advance the sequence in a rolled-back transaction - should be replicated
+$node_publisher->safe_psql(
+	'postgres', qq(
+	BEGIN;
+	SELECT nextval('s') FROM generate_series(1,100);
+	ROLLBACK;
+));
+
+$node_publisher->wait_for_catchup('seq_sub');
+
+# Check the data on subscriber
+$result = $node_subscriber->safe_psql(
+	'postgres', qq(
+	SELECT * FROM s;
+));
+
+is( $result, '231|0|t',
+	'check replicated sequence values on subscriber');
+
+
+# create a new sequence and roll it back - should not be replicated, due to
+# the transactional behavior
+$node_publisher->safe_psql(
+	'postgres', qq(
+	BEGIN;
+	CREATE SEQUENCE s2;
+	ALTER PUBLICATION seq_pub ADD SEQUENCE s2;
+	SELECT nextval('s2') FROM generate_series(1,100);
+	ROLLBACK;
+));
+
+$node_publisher->wait_for_catchup('seq_sub');
+
+# Check the data on subscriber
+$result = $node_subscriber->safe_psql(
+	'postgres', qq(
+	SELECT * FROM s2;
+));
+
+is( $result, '1|0|f',
+	'check replicated sequence values on subscriber');
+
+
+# create a new sequence, advance it in a rolled-back transaction, but commit
+# the create - the advance should be replicated nevertheless
+$node_publisher->safe_psql(
+	'postgres', qq(
+	BEGIN;
+	CREATE SEQUENCE s2;
+	ALTER PUBLICATION seq_pub ADD SEQUENCE s2;
+	SAVEPOINT sp1;
+	SELECT nextval('s2') FROM generate_series(1,100);
+	ROLLBACK TO sp1;
+	COMMIT;
+));
+
+$node_publisher->wait_for_catchup('seq_sub');
+
+# Wait for sync of the second sequence we just added to finish
+$synced_query =
+  "SELECT count(1) = 0 FROM pg_subscription_rel WHERE srsubstate NOT IN ('s', 'r');";
+$node_subscriber->poll_query_until('postgres', $synced_query)
+  or die "Timed out while waiting for subscriber to synchronize data";
+
+# Check the data on subscriber
+$result = $node_subscriber->safe_psql(
+	'postgres', qq(
+	SELECT * FROM s2;
+));
+
+is( $result, '132|0|t',
+	'check replicated sequence values on subscriber');
+
+
+# advance the new sequence in a transaction, and roll it back - in this case
+# it should be replicated as the behavior is non-transactional
+$node_publisher->safe_psql(
+	'postgres', qq(
+	BEGIN;
+	SELECT nextval('s2') FROM generate_series(1,100);
+	ROLLBACK;
+));
+
+$node_publisher->wait_for_catchup('seq_sub');
+
+# Check the data on subscriber
+$result = $node_subscriber->safe_psql(
+	'postgres', qq(
+	SELECT * FROM s2;
+));
+
+is( $result, '231|0|t',
+	'check replicated sequence values on subscriber');
+
+
+# advance the sequence in a subtransaction - the subtransaction gets rolled
+# back, but commit the main one - the changes should still be replicated
+$node_publisher->safe_psql(
+	'postgres', qq(
+	BEGIN;
+	SAVEPOINT s1;
+	SELECT nextval('s2') FROM generate_series(1,100);
+	ROLLBACK TO s1;
+	COMMIT;
+));
+
+$node_publisher->wait_for_catchup('seq_sub');
+
+# Check the data on subscriber
+$result = $node_subscriber->safe_psql(
+	'postgres', qq(
+	SELECT * FROM s2;
+));
+
+is( $result, '330|0|t',
+	'check replicated sequence values on subscriber');
+
+
+$node_subscriber->stop('fast');
+$node_publisher->stop('fast');
-- 
2.31.1



  [text/x-patch] 0003-Add-support-for-decoding-sequences-to-test_-20211118.patch (20.7K, ../[email protected]/3-0003-Add-support-for-decoding-sequences-to-test_-20211118.patch)
  download | inline diff:
From 0666c3a34955fc2edb811b36c081d271855d569e Mon Sep 17 00:00:00 2001
From: Tomas Vondra <[email protected]>
Date: Fri, 24 Sep 2021 00:42:04 +0200
Subject: [PATCH 3/4] Add support for decoding sequences to test_decoding

---
 contrib/test_decoding/Makefile              |   3 +-
 contrib/test_decoding/expected/sequence.out | 327 ++++++++++++++++++++
 contrib/test_decoding/sql/sequence.sql      | 119 +++++++
 contrib/test_decoding/test_decoding.c       |  69 +++++
 4 files changed, 517 insertions(+), 1 deletion(-)
 create mode 100644 contrib/test_decoding/expected/sequence.out
 create mode 100644 contrib/test_decoding/sql/sequence.sql

diff --git a/contrib/test_decoding/Makefile b/contrib/test_decoding/Makefile
index 9a31e0b879..56ddc3abae 100644
--- a/contrib/test_decoding/Makefile
+++ b/contrib/test_decoding/Makefile
@@ -5,7 +5,8 @@ PGFILEDESC = "test_decoding - example of a logical decoding output plugin"
 
 REGRESS = ddl xact rewrite toast permissions decoding_in_xact \
 	decoding_into_rel binary prepared replorigin time messages \
-	spill slot truncate stream stats twophase twophase_stream
+	spill slot truncate stream stats twophase twophase_stream \
+	sequence
 ISOLATION = mxact delayed_startup ondisk_startup concurrent_ddl_dml \
 	oldest_xmin snapshot_transfer subxact_without_top concurrent_stream \
 	twophase_snapshot
diff --git a/contrib/test_decoding/expected/sequence.out b/contrib/test_decoding/expected/sequence.out
new file mode 100644
index 0000000000..beecc3e0c8
--- /dev/null
+++ b/contrib/test_decoding/expected/sequence.out
@@ -0,0 +1,327 @@
+-- predictability
+SET synchronous_commit = on;
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+ ?column? 
+----------
+ init
+(1 row)
+
+CREATE SEQUENCE test_sequence;
+-- test the sequence changes by several nextval() calls
+SELECT nextval('test_sequence');
+ nextval 
+---------
+       1
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+       2
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+       3
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+       4
+(1 row)
+
+-- test the sequence changes by several ALTER commands
+ALTER SEQUENCE test_sequence INCREMENT BY 10;
+SELECT nextval('test_sequence');
+ nextval 
+---------
+      14
+(1 row)
+
+ALTER SEQUENCE test_sequence START WITH 3000;
+ALTER SEQUENCE test_sequence MAXVALUE 10000;
+ALTER SEQUENCE test_sequence RESTART WITH 4000;
+SELECT nextval('test_sequence');
+ nextval 
+---------
+    4000
+(1 row)
+
+-- test the sequence changes by several setval() calls
+SELECT setval('test_sequence', 3500);
+ setval 
+--------
+   3500
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+    3510
+(1 row)
+
+SELECT setval('test_sequence', 3500, true);
+ setval 
+--------
+   3500
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+    3510
+(1 row)
+
+SELECT setval('test_sequence', 3500, false);
+ setval 
+--------
+   3500
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+    3500
+(1 row)
+
+-- show results and drop sequence
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '0', 'skip-sequences', '0');
+                                              data                                              
+------------------------------------------------------------------------------------------------
+ BEGIN
+ sequence public.test_sequence: transactional:1 created:1 last_value:1 log_cnt:0 is_called:0
+ COMMIT
+ sequence public.test_sequence: transactional:0 created:0 last_value:33 log_cnt:0 is_called:1
+ BEGIN
+ sequence public.test_sequence: transactional:1 created:1 last_value:4 log_cnt:0 is_called:1
+ COMMIT
+ sequence public.test_sequence: transactional:0 created:0 last_value:334 log_cnt:0 is_called:1
+ BEGIN
+ sequence public.test_sequence: transactional:1 created:1 last_value:14 log_cnt:32 is_called:1
+ COMMIT
+ BEGIN
+ sequence public.test_sequence: transactional:1 created:1 last_value:14 log_cnt:0 is_called:1
+ COMMIT
+ BEGIN
+ sequence public.test_sequence: transactional:1 created:1 last_value:4000 log_cnt:0 is_called:0
+ COMMIT
+ sequence public.test_sequence: transactional:0 created:0 last_value:4320 log_cnt:0 is_called:1
+ sequence public.test_sequence: transactional:0 created:0 last_value:3500 log_cnt:0 is_called:1
+ sequence public.test_sequence: transactional:0 created:0 last_value:3830 log_cnt:0 is_called:1
+ sequence public.test_sequence: transactional:0 created:0 last_value:3500 log_cnt:0 is_called:1
+ sequence public.test_sequence: transactional:0 created:0 last_value:3830 log_cnt:0 is_called:1
+ sequence public.test_sequence: transactional:0 created:0 last_value:3500 log_cnt:0 is_called:0
+ sequence public.test_sequence: transactional:0 created:0 last_value:3820 log_cnt:0 is_called:1
+(24 rows)
+
+DROP SEQUENCE test_sequence;
+-- rollback on sequence creation and update
+BEGIN;
+CREATE SEQUENCE test_sequence;
+CREATE TABLE test_table (a INT);
+SELECT nextval('test_sequence');
+ nextval 
+---------
+       1
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+       2
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+       3
+(1 row)
+
+SELECT setval('test_sequence', 3000);
+ setval 
+--------
+   3000
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+    3001
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+    3002
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+    3003
+(1 row)
+
+ALTER SEQUENCE test_sequence RESTART WITH 6000;
+INSERT INTO test_table VALUES( (SELECT nextval('test_sequence')) );
+SELECT nextval('test_sequence');
+ nextval 
+---------
+    6001
+(1 row)
+
+ROLLBACK;
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'skip-sequences', '0');
+ data 
+------
+(0 rows)
+
+-- rollback on table creation with serial column 
+BEGIN;
+CREATE TABLE test_table (a SERIAL, b INT);
+INSERT INTO test_table (b) VALUES (100);
+INSERT INTO test_table (b) VALUES (200);
+INSERT INTO test_table (b) VALUES (300);
+SELECT setval('test_table_a_seq', 3000);
+ setval 
+--------
+   3000
+(1 row)
+
+INSERT INTO test_table (b) VALUES (400);
+INSERT INTO test_table (b) VALUES (500);
+INSERT INTO test_table (b) VALUES (600);
+ALTER SEQUENCE test_table_a_seq RESTART WITH 6000;
+INSERT INTO test_table (b) VALUES (700);
+INSERT INTO test_table (b) VALUES (800);
+INSERT INTO test_table (b) VALUES (900);
+ROLLBACK;
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'skip-sequences', '0');
+ data 
+------
+(0 rows)
+
+-- rollback on table with serial column 
+CREATE TABLE test_table (a SERIAL, b INT);
+BEGIN;
+INSERT INTO test_table (b) VALUES (100);
+INSERT INTO test_table (b) VALUES (200);
+INSERT INTO test_table (b) VALUES (300);
+SELECT setval('test_table_a_seq', 3000);
+ setval 
+--------
+   3000
+(1 row)
+
+INSERT INTO test_table (b) VALUES (400);
+INSERT INTO test_table (b) VALUES (500);
+INSERT INTO test_table (b) VALUES (600);
+ALTER SEQUENCE test_table_a_seq RESTART WITH 6000;
+INSERT INTO test_table (b) VALUES (700);
+INSERT INTO test_table (b) VALUES (800);
+INSERT INTO test_table (b) VALUES (900);
+ROLLBACK;
+-- check table and sequence values after rollback 
+SELECT * from test_table_a_seq;
+ last_value | log_cnt | is_called 
+------------+---------+-----------
+       3003 |      30 | t
+(1 row)
+
+SELECT nextval('test_table_a_seq');
+ nextval 
+---------
+    3004
+(1 row)
+
+DROP TABLE test_table;
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '0', 'skip-sequences', '0');
+                                               data                                                
+---------------------------------------------------------------------------------------------------
+ BEGIN
+ sequence public.test_table_a_seq: transactional:1 created:1 last_value:1 log_cnt:0 is_called:0
+ COMMIT
+ sequence public.test_table_a_seq: transactional:0 created:0 last_value:33 log_cnt:0 is_called:1
+ sequence public.test_table_a_seq: transactional:0 created:0 last_value:3000 log_cnt:0 is_called:1
+ sequence public.test_table_a_seq: transactional:0 created:0 last_value:3033 log_cnt:0 is_called:1
+ BEGIN
+ COMMIT
+(8 rows)
+
+-- savepoint test on table with serial column
+BEGIN;
+CREATE TABLE test_table (a SERIAL, b INT);
+INSERT INTO test_table (b) VALUES (100);
+INSERT INTO test_table (b) VALUES (200);
+SAVEPOINT a;
+INSERT INTO test_table (b) VALUES (300);
+ROLLBACK TO SAVEPOINT a;
+DROP TABLE test_table;
+COMMIT;
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '0', 'skip-sequences', '0');
+                                              data                                               
+-------------------------------------------------------------------------------------------------
+ BEGIN
+ sequence public.test_table_a_seq: transactional:1 created:1 last_value:1 log_cnt:0 is_called:0
+ sequence public.test_table_a_seq: transactional:1 created:0 last_value:33 log_cnt:0 is_called:1
+ table public.test_table: INSERT: a[integer]:1 b[integer]:100
+ table public.test_table: INSERT: a[integer]:2 b[integer]:200
+ COMMIT
+(6 rows)
+
+-- savepoint test on table with serial column
+BEGIN;
+CREATE SEQUENCE test_sequence;
+SELECT nextval('test_sequence');
+ nextval 
+---------
+       1
+(1 row)
+
+SELECT setval('test_sequence', 3000);
+ setval 
+--------
+   3000
+(1 row)
+
+SELECT nextval('test_sequence');
+ nextval 
+---------
+    3001
+(1 row)
+
+SAVEPOINT a;
+ALTER SEQUENCE test_sequence START WITH 7000;
+SELECT setval('test_sequence', 5000);
+ setval 
+--------
+   5000
+(1 row)
+
+ROLLBACK TO SAVEPOINT a;
+SELECT * FROM test_sequence;
+ last_value | log_cnt | is_called 
+------------+---------+-----------
+       3001 |      32 | t
+(1 row)
+
+DROP SEQUENCE test_sequence;
+COMMIT;
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '0', 'skip-sequences', '0');
+                                              data                                              
+------------------------------------------------------------------------------------------------
+ BEGIN
+ sequence public.test_sequence: transactional:1 created:1 last_value:1 log_cnt:0 is_called:0
+ sequence public.test_sequence: transactional:1 created:0 last_value:33 log_cnt:0 is_called:1
+ sequence public.test_sequence: transactional:1 created:0 last_value:3000 log_cnt:0 is_called:1
+ sequence public.test_sequence: transactional:1 created:0 last_value:3033 log_cnt:0 is_called:1
+ COMMIT
+(6 rows)
+
+SELECT pg_drop_replication_slot('regression_slot');
+ pg_drop_replication_slot 
+--------------------------
+ 
+(1 row)
+
diff --git a/contrib/test_decoding/sql/sequence.sql b/contrib/test_decoding/sql/sequence.sql
new file mode 100644
index 0000000000..d8a34738f3
--- /dev/null
+++ b/contrib/test_decoding/sql/sequence.sql
@@ -0,0 +1,119 @@
+-- predictability
+SET synchronous_commit = on;
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
+
+CREATE SEQUENCE test_sequence;
+
+-- test the sequence changes by several nextval() calls
+SELECT nextval('test_sequence');
+SELECT nextval('test_sequence');
+SELECT nextval('test_sequence');
+SELECT nextval('test_sequence');
+
+-- test the sequence changes by several ALTER commands
+ALTER SEQUENCE test_sequence INCREMENT BY 10;
+SELECT nextval('test_sequence');
+
+ALTER SEQUENCE test_sequence START WITH 3000;
+ALTER SEQUENCE test_sequence MAXVALUE 10000;
+ALTER SEQUENCE test_sequence RESTART WITH 4000;
+SELECT nextval('test_sequence');
+
+-- test the sequence changes by several setval() calls
+SELECT setval('test_sequence', 3500);
+SELECT nextval('test_sequence');
+SELECT setval('test_sequence', 3500, true);
+SELECT nextval('test_sequence');
+SELECT setval('test_sequence', 3500, false);
+SELECT nextval('test_sequence');
+
+-- show results and drop sequence
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '0', 'skip-sequences', '0');
+DROP SEQUENCE test_sequence;
+
+-- rollback on sequence creation and update
+BEGIN;
+CREATE SEQUENCE test_sequence;
+CREATE TABLE test_table (a INT);
+SELECT nextval('test_sequence');
+SELECT nextval('test_sequence');
+SELECT nextval('test_sequence');
+SELECT setval('test_sequence', 3000);
+SELECT nextval('test_sequence');
+SELECT nextval('test_sequence');
+SELECT nextval('test_sequence');
+ALTER SEQUENCE test_sequence RESTART WITH 6000;
+INSERT INTO test_table VALUES( (SELECT nextval('test_sequence')) );
+SELECT nextval('test_sequence');
+ROLLBACK;
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'skip-sequences', '0');
+
+-- rollback on table creation with serial column 
+BEGIN;
+CREATE TABLE test_table (a SERIAL, b INT);
+INSERT INTO test_table (b) VALUES (100);
+INSERT INTO test_table (b) VALUES (200);
+INSERT INTO test_table (b) VALUES (300);
+SELECT setval('test_table_a_seq', 3000);
+INSERT INTO test_table (b) VALUES (400);
+INSERT INTO test_table (b) VALUES (500);
+INSERT INTO test_table (b) VALUES (600);
+ALTER SEQUENCE test_table_a_seq RESTART WITH 6000;
+INSERT INTO test_table (b) VALUES (700);
+INSERT INTO test_table (b) VALUES (800);
+INSERT INTO test_table (b) VALUES (900);
+ROLLBACK;
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1', 'skip-sequences', '0');
+
+-- rollback on table with serial column 
+CREATE TABLE test_table (a SERIAL, b INT);
+
+BEGIN;
+INSERT INTO test_table (b) VALUES (100);
+INSERT INTO test_table (b) VALUES (200);
+INSERT INTO test_table (b) VALUES (300);
+SELECT setval('test_table_a_seq', 3000);
+INSERT INTO test_table (b) VALUES (400);
+INSERT INTO test_table (b) VALUES (500);
+INSERT INTO test_table (b) VALUES (600);
+ALTER SEQUENCE test_table_a_seq RESTART WITH 6000;
+INSERT INTO test_table (b) VALUES (700);
+INSERT INTO test_table (b) VALUES (800);
+INSERT INTO test_table (b) VALUES (900);
+ROLLBACK;
+
+-- check table and sequence values after rollback 
+SELECT * from test_table_a_seq;
+SELECT nextval('test_table_a_seq');
+
+DROP TABLE test_table;
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '0', 'skip-sequences', '0');
+
+-- savepoint test on table with serial column
+BEGIN;
+CREATE TABLE test_table (a SERIAL, b INT);
+INSERT INTO test_table (b) VALUES (100);
+INSERT INTO test_table (b) VALUES (200);
+SAVEPOINT a;
+INSERT INTO test_table (b) VALUES (300);
+ROLLBACK TO SAVEPOINT a;
+DROP TABLE test_table;
+COMMIT;
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '0', 'skip-sequences', '0');
+
+-- savepoint test on table with serial column
+BEGIN;
+CREATE SEQUENCE test_sequence;
+SELECT nextval('test_sequence');
+SELECT setval('test_sequence', 3000);
+SELECT nextval('test_sequence');
+SAVEPOINT a;
+ALTER SEQUENCE test_sequence START WITH 7000;
+SELECT setval('test_sequence', 5000);
+ROLLBACK TO SAVEPOINT a;
+SELECT * FROM test_sequence;
+DROP SEQUENCE test_sequence;
+COMMIT;
+SELECT data FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '0', 'skip-sequences', '0');
+
+SELECT pg_drop_replication_slot('regression_slot');
diff --git a/contrib/test_decoding/test_decoding.c b/contrib/test_decoding/test_decoding.c
index e5cd84e85e..45765d299e 100644
--- a/contrib/test_decoding/test_decoding.c
+++ b/contrib/test_decoding/test_decoding.c
@@ -35,6 +35,7 @@ typedef struct
 	bool		include_timestamp;
 	bool		skip_empty_xacts;
 	bool		only_local;
+	bool		skip_sequences;
 } TestDecodingData;
 
 /*
@@ -76,6 +77,10 @@ static void pg_decode_message(LogicalDecodingContext *ctx,
 							  ReorderBufferTXN *txn, XLogRecPtr message_lsn,
 							  bool transactional, const char *prefix,
 							  Size sz, const char *message);
+static void pg_decode_sequence(LogicalDecodingContext *ctx,
+							  ReorderBufferTXN *txn, XLogRecPtr sequence_lsn,
+							  Relation rel, bool transactional, bool created,
+							  int64 last_value, int64 log_cnt, bool is_called);
 static bool pg_decode_filter_prepare(LogicalDecodingContext *ctx,
 									 TransactionId xid,
 									 const char *gid);
@@ -116,6 +121,10 @@ static void pg_decode_stream_message(LogicalDecodingContext *ctx,
 									 ReorderBufferTXN *txn, XLogRecPtr message_lsn,
 									 bool transactional, const char *prefix,
 									 Size sz, const char *message);
+static void pg_decode_stream_sequence(LogicalDecodingContext *ctx,
+									  ReorderBufferTXN *txn, XLogRecPtr sequence_lsn,
+									  Relation rel, bool transactional, bool created,
+									  int64 last_value, int64 log_cnt, bool is_called);
 static void pg_decode_stream_truncate(LogicalDecodingContext *ctx,
 									  ReorderBufferTXN *txn,
 									  int nrelations, Relation relations[],
@@ -141,6 +150,7 @@ _PG_output_plugin_init(OutputPluginCallbacks *cb)
 	cb->filter_by_origin_cb = pg_decode_filter;
 	cb->shutdown_cb = pg_decode_shutdown;
 	cb->message_cb = pg_decode_message;
+	cb->sequence_cb = pg_decode_sequence;
 	cb->filter_prepare_cb = pg_decode_filter_prepare;
 	cb->begin_prepare_cb = pg_decode_begin_prepare_txn;
 	cb->prepare_cb = pg_decode_prepare_txn;
@@ -153,6 +163,7 @@ _PG_output_plugin_init(OutputPluginCallbacks *cb)
 	cb->stream_commit_cb = pg_decode_stream_commit;
 	cb->stream_change_cb = pg_decode_stream_change;
 	cb->stream_message_cb = pg_decode_stream_message;
+	cb->stream_sequence_cb = pg_decode_stream_sequence;
 	cb->stream_truncate_cb = pg_decode_stream_truncate;
 }
 
@@ -175,6 +186,9 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 	data->skip_empty_xacts = false;
 	data->only_local = false;
 
+	/* skip sequences by default for backwards compatibility */
+	data->skip_sequences = true;
+
 	ctx->output_plugin_private = data;
 
 	opt->output_type = OUTPUT_PLUGIN_TEXTUAL_OUTPUT;
@@ -265,6 +279,17 @@ pg_decode_startup(LogicalDecodingContext *ctx, OutputPluginOptions *opt,
 						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
 								strVal(elem->arg), elem->defname)));
 		}
+		else if (strcmp(elem->defname, "skip-sequences") == 0)
+		{
+
+			if (elem->arg == NULL)
+				continue;	/* true by default */
+			else if (!parse_bool(strVal(elem->arg), &data->skip_sequences))
+				ereport(ERROR,
+						(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+						 errmsg("could not parse value \"%s\" for parameter \"%s\"",
+								strVal(elem->arg), elem->defname)));
+		}
 		else
 		{
 			ereport(ERROR,
@@ -744,6 +769,28 @@ pg_decode_message(LogicalDecodingContext *ctx,
 	OutputPluginWrite(ctx, true);
 }
 
+static void
+pg_decode_sequence(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
+				   XLogRecPtr sequence_lsn, Relation rel,
+				   bool transactional, bool created,
+				   int64 last_value, int64 log_cnt, bool is_called)
+{
+	TestDecodingData *data = ctx->output_plugin_private;
+
+	/* return if requested to skip_sequences */
+	if (data->skip_sequences)
+		return;
+
+	OutputPluginPrepareWrite(ctx, true);
+	appendStringInfoString(ctx->out, "sequence ");
+	appendStringInfoString(ctx->out,
+						   quote_qualified_identifier(get_namespace_name(get_rel_namespace(RelationGetRelid(rel))),
+													  RelationGetRelationName(rel)));
+	appendStringInfo(ctx->out, 	": transactional:%d created:%d last_value:%zu log_cnt:%zu is_called:%d",
+					 transactional, created, last_value, log_cnt, is_called);
+	OutputPluginWrite(ctx, true);
+}
+
 static void
 pg_decode_stream_start(LogicalDecodingContext *ctx,
 					   ReorderBufferTXN *txn)
@@ -943,6 +990,28 @@ pg_decode_stream_message(LogicalDecodingContext *ctx,
 	OutputPluginWrite(ctx, true);
 }
 
+static void
+pg_decode_stream_sequence(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
+						  XLogRecPtr sequence_lsn, Relation rel,
+						  bool transactional, bool created,
+						  int64 last_value, int64 log_cnt, bool is_called)
+{
+	TestDecodingData *data = ctx->output_plugin_private;
+
+	/* return if requested to skip_sequences */
+	if (data->skip_sequences)
+		return;
+
+	OutputPluginPrepareWrite(ctx, true);
+	appendStringInfoString(ctx->out, "streaming sequence ");
+	appendStringInfoString(ctx->out,
+						   quote_qualified_identifier(get_namespace_name(get_rel_namespace(RelationGetRelid(rel))),
+													  RelationGetRelationName(rel)));
+	appendStringInfo(ctx->out, 	": transactional:%d created:%d last_value:%zu log_cnt:%zu is_called:%d",
+					 transactional, created, last_value, log_cnt, is_called);
+	OutputPluginWrite(ctx, true);
+}
+
 /*
  * In streaming mode, we don't display the detailed information of Truncate.
  * See pg_decode_stream_change.
-- 
2.31.1



  [text/x-patch] 0002-rework-20211118.patch (35.4K, ../[email protected]/4-0002-rework-20211118.patch)
  download | inline diff:
From 43f63100b0e792a3f6e96c9c4f2218b27a731f52 Mon Sep 17 00:00:00 2001
From: Tomas Vondra <[email protected]>
Date: Thu, 18 Nov 2021 19:48:30 +0100
Subject: [PATCH 2/4] rework

---
 src/backend/access/rmgrdesc/logicalmsgdesc.c  |  13 ++
 src/backend/access/transam/xact.c             |   9 +
 src/backend/commands/sequence.c               | 180 +++++++++------
 src/backend/replication/logical/decode.c      | 104 +++------
 src/backend/replication/logical/message.c     |   3 +-
 .../replication/logical/reorderbuffer.c       | 213 ++++--------------
 src/include/commands/sequence.h               |   2 +
 src/include/replication/message.h             |  15 ++
 src/include/replication/reorderbuffer.h       |  10 +-
 9 files changed, 232 insertions(+), 317 deletions(-)

diff --git a/src/backend/access/rmgrdesc/logicalmsgdesc.c b/src/backend/access/rmgrdesc/logicalmsgdesc.c
index d64ce2e7ef..c84628cd54 100644
--- a/src/backend/access/rmgrdesc/logicalmsgdesc.c
+++ b/src/backend/access/rmgrdesc/logicalmsgdesc.c
@@ -40,6 +40,16 @@ logicalmsg_desc(StringInfo buf, XLogReaderState *record)
 			sep = " ";
 		}
 	}
+	else if (info == XLOG_LOGICAL_SEQUENCE)
+	{
+		xl_logical_sequence *xlrec = (xl_logical_sequence *) rec;
+
+		appendStringInfo(buf, "rel %u/%u/%u last: %lu log_cnt: %lu is_called: %d",
+						 xlrec->node.spcNode,
+						 xlrec->node.dbNode,
+						 xlrec->node.relNode,
+						 xlrec->last, xlrec->log_cnt, xlrec->is_called);
+	}
 }
 
 const char *
@@ -48,5 +58,8 @@ logicalmsg_identify(uint8 info)
 	if ((info & ~XLR_INFO_MASK) == XLOG_LOGICAL_MESSAGE)
 		return "MESSAGE";
 
+	if ((info & ~XLR_INFO_MASK) == XLOG_LOGICAL_SEQUENCE)
+		return "SEQUENCE";
+
 	return NULL;
 }
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 8e35c432f5..eac8180250 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -36,6 +36,7 @@
 #include "catalog/storage.h"
 #include "commands/async.h"
 #include "commands/tablecmds.h"
+#include "commands/sequence.h"
 #include "commands/trigger.h"
 #include "executor/spi.h"
 #include "libpq/be-fsstubs.h"
@@ -2220,6 +2221,9 @@ CommitTransaction(void)
 	/* Prevent cancel/die interrupt while cleaning up */
 	HOLD_INTERRUPTS();
 
+	/* Write state of sequences to WAL */
+	AtEOXact_Sequences(true);
+
 	/* Commit updates to the relation map --- do this as late as possible */
 	AtEOXact_RelationMap(true, is_parallel_worker);
 
@@ -2378,6 +2382,8 @@ CommitTransaction(void)
  *	PrepareTransaction
  *
  * NB: if you change this routine, better look at CommitTransaction too!
+ *
+ * XXX Does this need to do something about logging of sequences?
  */
 static void
 PrepareTransaction(void)
@@ -2776,6 +2782,9 @@ AbortTransaction(void)
 	AtEOXact_RelationMap(false, is_parallel_worker);
 	AtAbort_Twophase();
 
+	/* XXX not sure we need to do anything about sequences at abort */
+	AtEOXact_Sequences(false);
+
 	/*
 	 * Advertise the fact that we aborted in pg_xact (assuming that we got as
 	 * far as assigning an XID to advertise).  But if we're inside a parallel
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index a98fcc2e97..92d1966f34 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -37,6 +37,7 @@
 #include "miscadmin.h"
 #include "nodes/makefuncs.h"
 #include "parser/parse_type.h"
+#include "replication/message.h"
 #include "storage/lmgr.h"
 #include "storage/proc.h"
 #include "storage/smgr.h"
@@ -75,6 +76,7 @@ typedef struct SeqTableData
 {
 	Oid			relid;			/* pg_class OID of this sequence (hash key) */
 	Oid			filenode;		/* last seen relfilenode of this sequence */
+	Oid			tablespace;		/* last seen tablespace of this sequence */
 	LocalTransactionId lxid;	/* xact in which we last did a seq op */
 	bool		last_valid;		/* do we have a valid "last" value? */
 	int64		last;			/* value last returned by nextval */
@@ -82,6 +84,10 @@ typedef struct SeqTableData
 	/* if last != cached, we have not used up all the cached values */
 	int64		increment;		/* copy of sequence's increment field */
 	/* note that increment is zero until we first do nextval_internal() */
+	bool		need_log;		/* should be written to WAL at commit? */
+	bool		touched;
+	int64		log_cnt;
+	bool		is_called;
 } SeqTableData;
 
 typedef SeqTableData *SeqTable;
@@ -94,7 +100,7 @@ static HTAB *seqhashtab = NULL; /* hash table for SeqTable items */
  */
 static SeqTableData *last_used_seq = NULL;
 
-static void fill_seq_with_data(Relation rel, HeapTuple tuple, bool create);
+static void fill_seq_with_data(Relation rel, HeapTuple tuple);
 static Relation lock_and_open_sequence(SeqTable seq);
 static void create_seq_hashtable(void);
 static void init_sequence(Oid relid, SeqTable *p_elm, Relation *p_rel);
@@ -222,7 +228,7 @@ DefineSequence(ParseState *pstate, CreateSeqStmt *seq)
 
 	/* now initialize the sequence's data */
 	tuple = heap_form_tuple(tupDesc, value, null);
-	fill_seq_with_data(rel, tuple, true);
+	fill_seq_with_data(rel, tuple);
 
 	/* process OWNED BY if given */
 	if (owned_by)
@@ -327,12 +333,17 @@ ResetSequence(Oid seq_relid)
 	/*
 	 * Insert the modified tuple into the new storage file.
 	 */
-	fill_seq_with_data(seq_rel, tuple, true);
+	fill_seq_with_data(seq_rel, tuple);
 
 	/* Clear local cache so that we don't think we have cached numbers */
 	/* Note that we do not change the currval() state */
 	elm->cached = elm->last;
 
+	/* Remember we need to write the sequence to WAL at commit. */
+	elm->need_log = true;
+	elm->is_called = false;
+	elm->log_cnt = 0;
+
 	relation_close(seq_rel, NoLock);
 }
 
@@ -340,7 +351,7 @@ ResetSequence(Oid seq_relid)
  * Initialize a sequence's relation with the specified tuple as content
  */
 static void
-fill_seq_with_data(Relation rel, HeapTuple tuple, bool create)
+fill_seq_with_data(Relation rel, HeapTuple tuple)
 {
 	Buffer		buf;
 	Page		page;
@@ -380,27 +391,7 @@ fill_seq_with_data(Relation rel, HeapTuple tuple, bool create)
 	if (RelationNeedsWAL(rel))
 	{
 		GetTopTransactionId();
-
-		/*
-		 * Ensure we have a proper XID, which will be included in the XLOG
-		 * record by XLogRecordAssemble. Otherwise the first nextval() in
-		 * a subxact (without any preceding changes) would get XID 0,
-		 * and it'd be impossible to decide which top xact it belongs to.
-		 * It'd also trigger assert in DecodeSequence.
-		 *
-		 * XXX This might seem unnecessary, because if there's no XID the
-		 * transaction couldn't have done anything important yet, e.g. it
-		 * could not have created a sequence. But that's incorrect, as it
-		 * ignores subtransactions. The current subtransaction might not
-		 * have done anything yet (thus no XID), but an earlier one might
-		 * have created the sequence.
-		 *
-		 * XXX Not sure if this is the best solution. Maybe do this only
-		 * with wal_level=logical to minimize the overhead. OTOH advancing
-		 * the sequence is likely followed by using the value(s) for some
-		 * other activity, which assigns the XID.
-		 */
-		GetCurrentTransactionId();
+		// GetCurrentTransactionId();
 	}
 
 	START_CRIT_SECTION();
@@ -422,7 +413,6 @@ fill_seq_with_data(Relation rel, HeapTuple tuple, bool create)
 		XLogRegisterBuffer(0, buf, REGBUF_WILL_INIT);
 
 		xlrec.node = rel->rd_node;
-		xlrec.created = create;
 
 		XLogRegisterData((char *) &xlrec, sizeof(xl_seq_rec));
 		XLogRegisterData((char *) tuple->t_data, tuple->t_len);
@@ -526,7 +516,11 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
 		/*
 		 * Insert the modified tuple into the new storage file.
 		 */
-		fill_seq_with_data(seqrel, newdatatuple, true);
+		fill_seq_with_data(seqrel, newdatatuple);
+
+		elm->need_log = true;
+		elm->is_called = false;
+		elm->log_cnt = 0;
 	}
 
 	/* process OWNED BY if given */
@@ -792,27 +786,7 @@ nextval_internal(Oid relid, bool check_permissions)
 	if (logit && RelationNeedsWAL(seqrel))
 	{
 		GetTopTransactionId();
-
-		/*
-		 * Ensure we have a proper XID, which will be included in the XLOG
-		 * record by XLogRecordAssemble. Otherwise the first nextval() in
-		 * a subxact (without any preceding changes) would get XID 0,
-		 * and it'd be impossible to decide which top xact it belongs to.
-		 * It'd also trigger assert in DecodeSequence.
-		 *
-		 * XXX This might seem unnecessary, because if there's no XID the
-		 * transaction couldn't have done anything important yet, e.g. it
-		 * could not have created a sequence. But that's incorrect, as it
-		 * ignores subtransactions. The current subtransaction might not
-		 * have done anything yet (thus no XID), but an earlier one might
-		 * have created the sequence.
-		 *
-		 * XXX Not sure if this is the best solution. Maybe do this only
-		 * with wal_level=logical to minimize the overhead. OTOH advancing
-		 * the sequence is likely followed by using the value(s) for some
-		 * other activity, which assigns the XID.
-		 */
-		GetCurrentTransactionId();
+		// GetCurrentTransactionId();
 	}
 
 	/* ready to change the on-disk (or really, in-buffer) tuple */
@@ -850,7 +824,6 @@ nextval_internal(Oid relid, bool check_permissions)
 		seq->log_cnt = 0;
 
 		xlrec.node = seqrel->rd_node;
-		xlrec.created = false;
 
 		XLogRegisterData((char *) &xlrec, sizeof(xl_seq_rec));
 		XLogRegisterData((char *) seqdatatuple.t_data, seqdatatuple.t_len);
@@ -858,6 +831,10 @@ nextval_internal(Oid relid, bool check_permissions)
 		recptr = XLogInsert(RM_SEQ_ID, XLOG_SEQ_LOG);
 
 		PageSetLSN(page, recptr);
+
+		elm->need_log = true;
+		elm->is_called = true;
+		elm->log_cnt = 0;
 	}
 
 	/* Now update sequence tuple to the intended final state */
@@ -1027,27 +1004,7 @@ do_setval(Oid relid, int64 next, bool iscalled)
 	if (RelationNeedsWAL(seqrel))
 	{
 		GetTopTransactionId();
-
-		/*
-		 * Ensure we have a proper XID, which will be included in the XLOG
-		 * record by XLogRecordAssemble. Otherwise the first nextval() in
-		 * a subxact (without any preceding changes) would get XID 0,
-		 * and it'd be impossible to decide which top xact it belongs to.
-		 * It'd also trigger assert in DecodeSequence.
-		 *
-		 * XXX This might seem unnecessary, because if there's no XID the
-		 * transaction couldn't have done anything important yet, e.g. it
-		 * could not have created a sequence. But that's incorrect, as it
-		 * ignores subtransactions. The current subtransaction might not
-		 * have done anything yet (thus no XID), but an earlier one might
-		 * have created the sequence.
-		 *
-		 * XXX Not sure if this is the best solution. Maybe do this only
-		 * with wal_level=logical to minimize the overhead. OTOH advancing
-		 * the sequence is likely followed by using the value(s) for some
-		 * other activity, which assigns the XID.
-		 */
-		GetCurrentTransactionId();
+		// GetCurrentTransactionId();
 	}
 
 	/* ready to change the on-disk (or really, in-buffer) tuple */
@@ -1070,14 +1027,16 @@ do_setval(Oid relid, int64 next, bool iscalled)
 		XLogRegisterBuffer(0, buf, REGBUF_WILL_INIT);
 
 		xlrec.node = seqrel->rd_node;
-		xlrec.created = false;
-
 		XLogRegisterData((char *) &xlrec, sizeof(xl_seq_rec));
 		XLogRegisterData((char *) seqdatatuple.t_data, seqdatatuple.t_len);
 
 		recptr = XLogInsert(RM_SEQ_ID, XLOG_SEQ_LOG);
 
 		PageSetLSN(page, recptr);
+
+		elm->need_log = true;
+		elm->is_called = false;
+		elm->log_cnt = 0;
 	}
 
 	END_CRIT_SECTION();
@@ -1196,11 +1155,14 @@ init_sequence(Oid relid, SeqTable *p_elm, Relation *p_rel)
 	{
 		/* relid already filled in */
 		elm->filenode = InvalidOid;
+		elm->tablespace = InvalidOid;
 		elm->lxid = InvalidLocalTransactionId;
 		elm->last_valid = false;
 		elm->last = elm->cached = 0;
 	}
 
+	elm->touched = true;
+
 	/*
 	 * Open the sequence relation.
 	 */
@@ -1219,6 +1181,7 @@ init_sequence(Oid relid, SeqTable *p_elm, Relation *p_rel)
 	 */
 	if (seqrel->rd_rel->relfilenode != elm->filenode)
 	{
+		elm->tablespace = seqrel->rd_rel->reltablespace;
 		elm->filenode = seqrel->rd_rel->relfilenode;
 		elm->cached = elm->last;
 	}
@@ -1977,6 +1940,8 @@ seq_redo(XLogReaderState *record)
 
 /*
  * Flush cached sequence information.
+ *
+ * XXX Do we need to WAL-log the entries based on need_log?
  */
 void
 ResetSequenceCaches(void)
@@ -2000,3 +1965,74 @@ seq_mask(char *page, BlockNumber blkno)
 
 	mask_unused_space(page);
 }
+
+/* XXX Do this only for wal_level = logical, probably? */
+void
+AtEOXact_Sequences(bool isCommit)
+{
+	SeqTable		entry;
+	HASH_SEQ_STATUS	scan;
+
+	if (!seqhashtab)
+		return;
+
+	/*
+	 * XXX If we run just nextval() that returns cached value, the xact may
+	 * not have XID, but we expect it in reorderbuffer. Maybe treat that as
+	 * transactional?
+	 */
+	// GetTopTransactionId();
+	// GetCurrentTransactionId();
+
+	hash_seq_init(&scan, seqhashtab);
+
+	while ((entry = (SeqTable) hash_seq_search(&scan)))
+	{
+		RelFileNode			rnode;
+		xl_logical_sequence	xlrec;
+
+		if (!isCommit)
+			entry->touched = false;
+
+		/*
+		 * If not touched in the current transaction, don't log anything.
+		 * We leave needs_log set, so that if future transactions touch
+		 * the sequence we'll log it properly.
+		 */
+		if (!entry->touched)
+			continue;
+
+		/*
+		 * Likewise, if the sequence does not need logging, we're done.
+		 */
+		if (!entry->need_log)
+			continue;
+
+		/* if this is commit, we'll log the */
+		entry->need_log = false;
+		entry->touched = false;
+
+		rnode.spcNode = entry->tablespace;		/* tablespace */
+		rnode.dbNode = MyDatabaseId;			/* database */
+		rnode.relNode = entry->filenode;		/* relation */
+
+		xlrec.node = rnode;
+		xlrec.reloid = entry->relid;
+
+		/* XXX is it good enough to log values we have in cache? seems
+		 * wrong and we may need to re-read that. */
+		// xlrec.dbId = MyDatabaseId;
+		// xlrec.relId = entry->relid;
+		xlrec.last = entry->last;
+		xlrec.log_cnt = entry->log_cnt;
+		xlrec.is_called = entry->is_called;
+
+		XLogBeginInsert();
+		XLogRegisterData((char *) &xlrec, SizeOfLogicalSequence);
+
+		/* allow origin filtering */
+		XLogSetRecordFlags(XLOG_INCLUDE_ORIGIN);
+
+		(void) XLogInsert(RM_LOGICALMSG_ID, XLOG_LOGICAL_SEQUENCE);
+	}
+}
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index b61f2e264a..d29844adf9 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -59,6 +59,9 @@ static void DecodeXactOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
 static void DecodeStandbyOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
 static void DecodeLogicalMsgOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
 
+static void DecodeLogicalMessage(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+static void DecodeLogicalSequence(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
+
 /* individual record(group)'s handlers */
 static void DecodeInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
 static void DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
@@ -75,11 +78,9 @@ static void DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 						bool two_phase);
 static void DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 						  xl_xact_parsed_prepare *parsed);
-static void DecodeSequence(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
 
 /* common function to decode tuples */
 static void DecodeXLogTuple(char *data, Size len, ReorderBufferTupleBuf *tup);
-static void DecodeSeqTuple(char *data, Size len, ReorderBufferTupleBuf *tuple);
 
 /* helper functions for decoding transactions */
 static inline bool FilterPrepare(LogicalDecodingContext *ctx,
@@ -160,10 +161,6 @@ LogicalDecodingProcessRecord(LogicalDecodingContext *ctx, XLogReaderState *recor
 			DecodeLogicalMsgOp(ctx, &buf);
 			break;
 
-		case RM_SEQ_ID:
-			DecodeSequence(ctx, &buf);
-			break;
-
 			/*
 			 * Rmgrs irrelevant for logical decoding; they describe stuff not
 			 * represented in logical decoding. Add new rmgrs in rmgrlist.h's
@@ -626,6 +623,27 @@ FilterByOrigin(LogicalDecodingContext *ctx, RepOriginId origin_id)
  */
 static void
 DecodeLogicalMsgOp(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	XLogReaderState *r = buf->record;
+	uint8		info = XLogRecGetInfo(r) & ~XLR_INFO_MASK;
+
+	switch (info)
+	{
+		case XLOG_LOGICAL_MESSAGE:
+			DecodeLogicalMessage(ctx, buf);
+			break;
+
+		case XLOG_LOGICAL_SEQUENCE:
+			DecodeLogicalSequence(ctx, buf);
+			break;
+
+		default:
+			elog(ERROR, "unexpected RM_LOGICALMSG_ID record type: %u", info);
+	}
+}
+
+static void
+DecodeLogicalMessage(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 {
 	SnapBuild  *builder = ctx->snapshot_builder;
 	XLogReaderState *r = buf->record;
@@ -1319,31 +1337,6 @@ DecodeTXNNeedSkip(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 			ctx->fast_forward || FilterByOrigin(ctx, origin_id));
 }
 
-/*
- * Decode Sequence Tuple
- */
-static void
-DecodeSeqTuple(char *data, Size len, ReorderBufferTupleBuf *tuple)
-{
-	int			datalen = len - sizeof(xl_seq_rec) - SizeofHeapTupleHeader;
-
-	Assert(datalen >= 0);
-
-	tuple->tuple.t_len = datalen + SizeofHeapTupleHeader;;
-
-	ItemPointerSetInvalid(&tuple->tuple.t_self);
-
-	tuple->tuple.t_tableOid = InvalidOid;
-
-	memcpy(((char *) tuple->tuple.t_data),
-		   data + sizeof(xl_seq_rec),
-		   SizeofHeapTupleHeader);
-
-	memcpy(((char *) tuple->tuple.t_data) + SizeofHeapTupleHeader,
-		   data + sizeof(xl_seq_rec) + SizeofHeapTupleHeader,
-		   datalen);
-}
-
 /*
  * Handle sequence decode
  *
@@ -1362,24 +1355,20 @@ DecodeSeqTuple(char *data, Size len, ReorderBufferTupleBuf *tuple)
  * plugin - it might get confused about which sequence it's related to etc.
  */
 static void
-DecodeSequence(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+DecodeLogicalSequence(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 {
 	SnapBuild  *builder = ctx->snapshot_builder;
-	ReorderBufferTupleBuf *tuplebuf;
 	RelFileNode target_node;
 	XLogReaderState *r = buf->record;
-	char	   *tupledata = NULL;
-	Size		tuplelen;
-	Size		datalen = 0;
 	TransactionId xid = XLogRecGetXid(r);
 	uint8		info = XLogRecGetInfo(buf->record) & ~XLR_INFO_MASK;
-	xl_seq_rec *xlrec;
+	xl_logical_sequence *xlrec;
 	Snapshot	snapshot;
 	RepOriginId origin_id = XLogRecGetOrigin(r);
-	bool		transactional;
+	bool		transactional = TransactionIdIsValid(xid);
 
 	/* only decode changes flagged with XLOG_SEQ_LOG */
-	if (info != XLOG_SEQ_LOG)
+	if (info != XLOG_LOGICAL_SEQUENCE)
 		elog(ERROR, "unexpected RM_SEQ_ID record type: %u", info);
 
 	/*
@@ -1390,8 +1379,11 @@ DecodeSequence(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 		ctx->fast_forward)
 		return;
 
+	/* extract the WAL record, with "created" flag */
+	xlrec = (xl_logical_sequence *) XLogRecGetData(r);
+
 	/* only interested in our database */
-	XLogRecGetBlockTag(r, 0, &target_node, NULL, NULL);
+	target_node = xlrec->node;
 	if (target_node.dbNode != ctx->slot->data.database)
 		return;
 
@@ -1399,44 +1391,18 @@ DecodeSequence(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 	if (FilterByOrigin(ctx, XLogRecGetOrigin(r)))
 		return;
 
-	tupledata = XLogRecGetData(r);
-	datalen = XLogRecGetDataLen(r);
-	tuplelen = datalen - SizeOfHeapHeader - sizeof(xl_seq_rec);
-
-	/* extract the WAL record, with "created" flag */
-	xlrec = (xl_seq_rec *) XLogRecGetData(r);
-
-	/* XXX how could we have sequence change without data? */
-	if(!datalen || !tupledata)
-		return;
-
-	tuplebuf = ReorderBufferGetTupleBuf(ctx->reorder, tuplelen);
-	DecodeSeqTuple(tupledata, datalen, tuplebuf);
-
-	/*
-	 * Should we handle the sequence increment as transactional or not?
-	 *
-	 * If the sequence was created in a still-running transaction, treat
-	 * it as transactional and queue the increments. Otherwise it needs
-	 * to be treated as non-transactional, in which case we send it to
-	 * the plugin right away.
-	 */
-	transactional = ReorderBufferSequenceIsTransactional(ctx->reorder,
-														 target_node,
-														 xlrec->created);
-
 	/* Skip the change if already processed (per the snapshot). */
 	if (transactional &&
 		!SnapBuildProcessChange(builder, xid, buf->origptr))
 		return;
 	else if (!transactional &&
 			 (SnapBuildCurrentState(builder) != SNAPBUILD_CONSISTENT ||
-			  SnapBuildXactNeedsSkip(builder, buf->origptr)))
+			 SnapBuildXactNeedsSkip(builder, buf->origptr)))
 		return;
 
 	/* Queue the increment (or send immediately if not transactional). */
 	snapshot = SnapBuildGetOrBuildSnapshot(builder, xid);
 	ReorderBufferQueueSequence(ctx->reorder, xid, snapshot, buf->endptr,
-							   origin_id, target_node, transactional,
-							   xlrec->created, tuplebuf);
+							   origin_id, xlrec->reloid, target_node,
+							   xlrec->last, xlrec->log_cnt, xlrec->is_called);
 }
diff --git a/src/backend/replication/logical/message.c b/src/backend/replication/logical/message.c
index 93bd372421..3f0ac57fc6 100644
--- a/src/backend/replication/logical/message.c
+++ b/src/backend/replication/logical/message.c
@@ -81,7 +81,8 @@ logicalmsg_redo(XLogReaderState *record)
 {
 	uint8		info = XLogRecGetInfo(record) & ~XLR_INFO_MASK;
 
-	if (info != XLOG_LOGICAL_MESSAGE)
+	if (info != XLOG_LOGICAL_MESSAGE &&
+		info != XLOG_LOGICAL_SEQUENCE)
 		elog(PANIC, "logicalmsg_redo: unknown op code %u", info);
 
 	/* This is only interesting for logical decoding, see decode.c. */
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 434926459f..1d9a39ac4b 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -569,17 +569,11 @@ ReorderBufferReturnChange(ReorderBuffer *rb, ReorderBufferChange *change,
 				change->data.truncate.relids = NULL;
 			}
 			break;
-		case REORDER_BUFFER_CHANGE_SEQUENCE:
-			if (change->data.sequence.tuple)
-			{
-				ReorderBufferReturnTupleBuf(rb, change->data.sequence.tuple);
-				change->data.sequence.tuple = NULL;
-			}
-			break;
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT:
 		case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
 		case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
+		case REORDER_BUFFER_CHANGE_SEQUENCE:
 			break;
 	}
 
@@ -973,9 +967,10 @@ ReorderBufferSequenceCleanup(ReorderBuffer *rb, TransactionId xid)
 void
 ReorderBufferQueueSequence(ReorderBuffer *rb, TransactionId xid,
 						   Snapshot snapshot, XLogRecPtr lsn, RepOriginId origin_id,
-						   RelFileNode rnode, bool transactional, bool created,
-						   ReorderBufferTupleBuf *tuplebuf)
+						   Oid reloid, RelFileNode rnode, int64 last, int64 log_cnt, bool is_called)
 {
+	bool transactional = TransactionIdIsValid(xid);
+
 	/*
 	 * Change needs to be handled as transactional, because the sequence was
 	 * created in a transaction that is still running. In that case all the
@@ -992,38 +987,6 @@ ReorderBufferQueueSequence(ReorderBuffer *rb, TransactionId xid,
 		MemoryContext oldcontext;
 		ReorderBufferChange *change;
 
-		/* lookup sequence by relfilenode */
-		ReorderBufferSequenceEnt   *ent;
-		bool						found;
-
-		/* transactional changes require a transaction */
-		Assert(xid != InvalidTransactionId);
-
-		/* search the lookup table (we ignore the return value, found is enough) */
-		ent = hash_search(rb->sequences,
-						  (void *) &rnode,
-						  created ? HASH_ENTER : HASH_FIND,
-						  &found);
-
-		/*
-		 * If this is the "create" increment, we must not have found any
-		 * pre-existing entry in the hash table (i.e. there must not be
-		 * any conflicting sequence).
-		 */
-		Assert(!(created && found));
-
-		/* But we must have either created or found an existing entry. */
-		Assert(created || found);
-
-		/*
-		 * When creating the sequence, remember the XID of the transaction
-		 * that created id.
-		 */
-		if (created)
-			ent->xid = xid;
-
-		/* XXX Maybe check that we're still in the same top-level xact? */
-
 		/* OK, allocate and queue the change */
 		oldcontext = MemoryContextSwitchTo(rb->context);
 
@@ -1034,38 +997,26 @@ ReorderBufferQueueSequence(ReorderBuffer *rb, TransactionId xid,
 
 		memcpy(&change->data.sequence.relnode, &rnode, sizeof(RelFileNode));
 
-		change->data.sequence.created = created;
-		change->data.sequence.tuple = tuplebuf;
+		change->data.sequence.reloid = reloid;
+		change->data.sequence.last = last;
+		change->data.sequence.log_cnt = log_cnt;
+		change->data.sequence.is_called = is_called;
 
 		/* add it to the same subxact that created the sequence */
-		ReorderBufferQueueChange(rb, ent->xid, lsn, change, false);
+		ReorderBufferQueueChange(rb, xid, lsn, change, false);
 
 		MemoryContextSwitchTo(oldcontext);
 	}
 	else
 	{
 		/*
-		 * This increment is for a sequence that was not created in any
-		 * running transaction, so we treat it as non-transactional and
-		 * just send it to the output plugin directly.
-		 */
+		* This increment is for a sequence that was not created in any
+		* running transaction, so we treat it as non-transactional and
+		* just send it to the output plugin directly.
+		*/
 		ReorderBufferTXN *txn = NULL;
 		volatile Snapshot snapshot_now = snapshot;
-		bool	using_subtxn;
-
-#ifdef USE_ASSERT_CHECKING
-		/* All "creates" have to be handled as transactional. */
-		Assert(!created);
-
-		/* Make sure the sequence is not in the hash table. */
-		{
-			bool	found;
-			hash_search(rb->sequences,
-						(void *) &rnode,
-						HASH_FIND, &found);
-			Assert(!found);
-		}
-#endif
+		bool    using_subtxn;
 
 		if (xid != InvalidTransactionId)
 			txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
@@ -1074,40 +1025,35 @@ ReorderBufferQueueSequence(ReorderBuffer *rb, TransactionId xid,
 		SetupHistoricSnapshot(snapshot_now, NULL);
 
 		/*
-		 * Decoding needs access to syscaches et al., which in turn use
-		 * heavyweight locks and such. Thus we need to have enough state around to
-		 * keep track of those.  The easiest way is to simply use a transaction
-		 * internally.  That also allows us to easily enforce that nothing writes
-		 * to the database by checking for xid assignments.
-		 *
-		 * When we're called via the SQL SRF there's already a transaction
-		 * started, so start an explicit subtransaction there.
-		 */
+		* Decoding needs access to syscaches et al., which in turn use
+		* heavyweight locks and such. Thus we need to have enough state around to
+		* keep track of those.  The easiest way is to simply use a transaction
+		* internally.  That also allows us to easily enforce that nothing writes
+		* to the database by checking for xid assignments.
+		*
+		* When we're called via the SQL SRF there's already a transaction
+		* started, so start an explicit subtransaction there.
+		*/
 		using_subtxn = IsTransactionOrTransactionBlock();
 
 		PG_TRY();
 		{
 			Relation	relation;
-			HeapTuple	tuple;
-			bool		isnull;
-			int64		last_value, log_cnt;
-			bool		is_called;
-			Oid			reloid;
+//			Oid			reloid;
 
 			if (using_subtxn)
 				BeginInternalSubTransaction("sequence");
 			else
 				StartTransactionCommand();
-
+/*
 			reloid = RelidByRelfilenode(rnode.spcNode, rnode.relNode);
 
 			if (reloid == InvalidOid)
 				elog(ERROR, "could not map filenode \"%s\" to relation OID",
-					 relpathperm(rnode,
-								 MAIN_FORKNUM));
-
+					relpathperm(rnode,
+								MAIN_FORKNUM));
+*/
 			relation = RelationIdGetRelation(reloid);
-			tuple = &tuplebuf->tuple;
 
 			/*
 			 * Extract the internal sequence values, describing the state.
@@ -1115,12 +1061,8 @@ ReorderBufferQueueSequence(ReorderBuffer *rb, TransactionId xid,
 			 * XXX Seems a bit strange to access it directly. Maybe there's
 			 * a better / more correct way?
 			 */
-			last_value = heap_getattr(tuple, 1, RelationGetDescr(relation), &isnull);
-			log_cnt = heap_getattr(tuple, 2, RelationGetDescr(relation), &isnull);
-			is_called = heap_getattr(tuple, 3, RelationGetDescr(relation), &isnull);
-
-			rb->sequence(rb, txn, lsn, relation, transactional, created,
-						 last_value, log_cnt, is_called);
+			rb->sequence(rb, txn, lsn, relation, transactional, false,
+						last, log_cnt, is_called);
 
 			RelationClose(relation);
 
@@ -2248,31 +2190,27 @@ ReorderBufferApplySequence(ReorderBuffer *rb, ReorderBufferTXN *txn,
 						   Relation relation, ReorderBufferChange *change,
 						   bool streaming)
 {
-	HeapTuple	tuple;
-	bool		isnull;
 	int64		last_value, log_cnt;
 	bool		is_called;
 
-	tuple = &change->data.sequence.tuple->tuple;
-
 	/*
 	 * Extract the internal sequence values, describing the state.
 	 *
 	 * XXX Seems a bit strange to access it directly. Maybe there's
 	 * a better / more correct way?
 	 */
-	last_value = heap_getattr(tuple, 1, RelationGetDescr(relation), &isnull);
-	log_cnt = heap_getattr(tuple, 2, RelationGetDescr(relation), &isnull);
-	is_called = heap_getattr(tuple, 3, RelationGetDescr(relation), &isnull);
+	last_value = change->data.sequence.last;
+	log_cnt = change->data.sequence.log_cnt;
+	is_called = change->data.sequence.is_called;
 
 	/* Only ever called from ReorderBufferApplySequence, so transational. */
 	if (streaming)
 		rb->stream_sequence(rb, txn, change->lsn, relation, true,
-							change->data.sequence.created,
+							false,	/* FIXME */
 							last_value, log_cnt, is_called);
 	else
 		rb->sequence(rb, txn, change->lsn, relation, true,
-					 change->data.sequence.created,
+					 false,	/* FIXME */
 					 last_value, log_cnt, is_called);
 }
 
@@ -2722,15 +2660,17 @@ ReorderBufferProcessTXN(ReorderBuffer *rb, ReorderBufferTXN *txn,
 				case REORDER_BUFFER_CHANGE_SEQUENCE:
 					Assert(snapshot_now);
 
+					/*
 					reloid = RelidByRelfilenode(change->data.sequence.relnode.spcNode,
 												change->data.sequence.relnode.relNode);
 
 					if (reloid == InvalidOid)
-						elog(ERROR, "could not map filenode \"%s\" to relation OID",
+						elog(ERROR, "zz could not map filenode \"%s\" to relation OID",
 							 relpathperm(change->data.sequence.relnode,
 										 MAIN_FORKNUM));
 
-					relation = RelationIdGetRelation(reloid);
+					*/
+					relation = RelationIdGetRelation(change->data.sequence.reloid);
 
 					if (!RelationIsValid(relation))
 						elog(ERROR, "could not open relation with OID %u (for filenode \"%s\")",
@@ -4127,45 +4067,13 @@ ReorderBufferSerializeChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
 				memcpy(data, change->data.truncate.relids, size);
 				data += size;
 
-				break;
-			}
-		case REORDER_BUFFER_CHANGE_SEQUENCE:
-			{
-				char	   *data;
-				ReorderBufferTupleBuf *tup;
-				Size		len = 0;
-
-				tup = change->data.sequence.tuple;
-
-				if (tup)
-				{
-					sz += sizeof(HeapTupleData);
-					len = tup->tuple.t_len;
-					sz += len;
-				}
-
-				/* make sure we have enough space */
-				ReorderBufferSerializeReserve(rb, sz);
-
-				data = ((char *) rb->outbuf) + sizeof(ReorderBufferDiskChange);
-				/* might have been reallocated above */
-				ondisk = (ReorderBufferDiskChange *) rb->outbuf;
-
-				if (len)
-				{
-					memcpy(data, &tup->tuple, sizeof(HeapTupleData));
-					data += sizeof(HeapTupleData);
-
-					memcpy(data, tup->tuple.t_data, len);
-					data += len;
-				}
-
 				break;
 			}
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT:
 		case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
 		case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
+		case REORDER_BUFFER_CHANGE_SEQUENCE:
 			/* ReorderBufferChange contains everything important */
 			break;
 	}
@@ -4424,28 +4332,13 @@ ReorderBufferChangeSize(ReorderBufferChange *change)
 			{
 				sz += sizeof(Oid) * change->data.truncate.nrelids;
 
-				break;
-			}
-		case REORDER_BUFFER_CHANGE_SEQUENCE:
-			{
-				ReorderBufferTupleBuf *tup;
-				Size		len = 0;
-
-				tup = change->data.sequence.tuple;
-
-				if (tup)
-				{
-					sz += sizeof(HeapTupleData);
-					len = tup->tuple.t_len;
-					sz += len;
-				}
-
 				break;
 			}
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT:
 		case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
 		case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
+		case REORDER_BUFFER_CHANGE_SEQUENCE:
 			/* ReorderBufferChange contains everything important */
 			break;
 	}
@@ -4742,33 +4635,11 @@ ReorderBufferRestoreChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
 				break;
 			}
 
-		case REORDER_BUFFER_CHANGE_SEQUENCE:
-			if (change->data.sequence.tuple)
-			{
-				uint32		tuplelen = ((HeapTuple) data)->t_len;
-
-				change->data.sequence.tuple =
-					ReorderBufferGetTupleBuf(rb, tuplelen - SizeofHeapTupleHeader);
-
-				/* restore ->tuple */
-				memcpy(&change->data.sequence.tuple->tuple, data,
-					   sizeof(HeapTupleData));
-				data += sizeof(HeapTupleData);
-
-				/* reset t_data pointer into the new tuplebuf */
-				change->data.sequence.tuple->tuple.t_data =
-					ReorderBufferTupleBufData(change->data.sequence.tuple);
-
-				/* restore tuple data itself */
-				memcpy(change->data.sequence.tuple->tuple.t_data, data, tuplelen);
-				data += tuplelen;
-			}
-			break;
-
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT:
 		case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
 		case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
+		case REORDER_BUFFER_CHANGE_SEQUENCE:
 			break;
 	}
 
diff --git a/src/include/commands/sequence.h b/src/include/commands/sequence.h
index 5919fb90ee..ddb36b5b17 100644
--- a/src/include/commands/sequence.h
+++ b/src/include/commands/sequence.h
@@ -62,6 +62,8 @@ extern void DeleteSequenceTuple(Oid relid);
 extern void ResetSequence(Oid seq_relid);
 extern void ResetSequenceCaches(void);
 
+extern void AtEOXact_Sequences(bool isCommit);
+
 extern void seq_redo(XLogReaderState *rptr);
 extern void seq_desc(StringInfo buf, XLogReaderState *rptr);
 extern const char *seq_identify(uint8 info);
diff --git a/src/include/replication/message.h b/src/include/replication/message.h
index d3fb324c81..a39e8e984d 100644
--- a/src/include/replication/message.h
+++ b/src/include/replication/message.h
@@ -27,13 +27,28 @@ typedef struct xl_logical_message
 	char		message[FLEXIBLE_ARRAY_MEMBER];
 } xl_logical_message;
 
+/*
+ * Generic logical decoding sequence wal record.
+ */
+typedef struct xl_logical_sequence
+{
+	RelFileNode	node;
+	Oid			reloid;
+	int64		last;			/* last value emitted for sequence */
+	int64		log_cnt;		/* last value cached for sequence */
+	bool		is_called;
+} xl_logical_sequence;
+
 #define SizeOfLogicalMessage	(offsetof(xl_logical_message, message))
+#define SizeOfLogicalSequence	(sizeof(xl_logical_sequence))
 
 extern XLogRecPtr LogLogicalMessage(const char *prefix, const char *message,
 									size_t size, bool transactional);
 
 /* RMGR API*/
 #define XLOG_LOGICAL_MESSAGE	0x00
+#define XLOG_LOGICAL_SEQUENCE	0x10
+
 void		logicalmsg_redo(XLogReaderState *record);
 void		logicalmsg_desc(StringInfo buf, XLogReaderState *record);
 const char *logicalmsg_identify(uint8 info);
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index 63e6ed037b..eb78d5dff4 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -164,8 +164,10 @@ typedef struct ReorderBufferChange
 		struct
 		{
 			RelFileNode relnode;
-			bool		created;
-			ReorderBufferTupleBuf *tuple;
+			Oid			reloid;
+			int64		last;
+			int64		log_cnt;
+			bool		is_called;
 		}			sequence;
 	}			data;
 
@@ -672,8 +674,8 @@ void		ReorderBufferQueueMessage(ReorderBuffer *, TransactionId, Snapshot snapsho
 									  Size message_size, const char *message);
 void		ReorderBufferQueueSequence(ReorderBuffer *rb, TransactionId xid,
 									   Snapshot snapshot, XLogRecPtr lsn, RepOriginId origin_id,
-									   RelFileNode rnode, bool transactional, bool created,
-									   ReorderBufferTupleBuf *tuplebuf);
+									   Oid reloid, RelFileNode rnode,
+									   int64 last, int64 log_cnt, bool is_called);
 void		ReorderBufferCommit(ReorderBuffer *, TransactionId,
 								XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
 								TimestampTz commit_time, RepOriginId origin_id, XLogRecPtr origin_lsn);
-- 
2.31.1



  [text/x-patch] 0001-Logical-decoding-of-sequences-20211118.patch (43.5K, ../[email protected]/5-0001-Logical-decoding-of-sequences-20211118.patch)
  download | inline diff:
From e61a7c9994133d1a0dc25c369c026205602b3314 Mon Sep 17 00:00:00 2001
From: Tomas Vondra <[email protected]>
Date: Fri, 24 Sep 2021 00:41:33 +0200
Subject: [PATCH 1/4] Logical decoding of sequences

This adds the infrastructure for logical decoding of sequences. Support
for built-in logical replication and test_decoding is added separately.

When decoding sequences, we differentiate between a sequences created in
a (running) transaction, and sequences created in other (already
committed) transactions. Changes for sequences created in the same
top-level transaction are treated as "transactional" i.e. just like any
other change from that transaction (and discarded in case of a
rollback). Changes for sequences created earlier are treated as not
transactional - are processed immediately, as if performed outside any
transaction (and thus not rolled back).

This mixed behavior is necessary - sequences are non-transactional (e.g.
ROLLBACK does not undo the sequence increments). But for new sequences,
we need to handle them in a transactional way, because if we ever get
some DDL support, the sequence won't exist until the transaction gets
applied. So we need to ensure the increments don't happen until the
sequence gets created.

To differentiate which sequences are "old" and which were created in a
still-running transaction, we track sequences created in running
transactions in a hash table. Each sequence is identified by it's
relfilenode, and at transaction commit we discard all sequences created
in that particular transaction. For each sequence we track the XID of
the (sub)transaction that created it, and we cleanup the sequences for
each subtransaction when it completes (commit/rollback).

We don't use the XID to check if it's the same top-level transaction.
It's enough to know it was created in an in-progress transaction, and we
know it must be the current one because otherwise it wouldn't see the
sequence object.

The main changes in this patch are:

1) ensure WAL-logging of all necessary info for sequence advances

We need to be able to associate the advance with a XID, but until now
sequence advance might have XID 0 if it was the first thing the
transaction did. So we ensure the transaction has XID.

Note: This is needed because of subxacts. A XID 0 might still have the
sequence created in a different subxact of the same top-level xact.

Then there's a "created" flag added to the xl_seq_rec, which is
necessary to differentiate WAL for created/reset sequences.

2) decoding / queueing of sequences into ReorderBuffer

This is mostly copy-paste of existing code for other decoded events.

3) tracking sequences created in in-progress transactions

We use a simple hash table, indexed by relfilenode.
---
 src/backend/commands/sequence.c               |  83 +++-
 src/backend/replication/logical/decode.c      | 131 +++++-
 src/backend/replication/logical/logical.c     |  89 ++++
 .../replication/logical/reorderbuffer.c       | 424 ++++++++++++++++++
 src/include/commands/sequence.h               |   1 +
 src/include/replication/output_plugin.h       |  29 ++
 src/include/replication/reorderbuffer.h       |  44 +-
 7 files changed, 793 insertions(+), 8 deletions(-)

diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index 72bfdc07a4..a98fcc2e97 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -94,7 +94,7 @@ static HTAB *seqhashtab = NULL; /* hash table for SeqTable items */
  */
 static SeqTableData *last_used_seq = NULL;
 
-static void fill_seq_with_data(Relation rel, HeapTuple tuple);
+static void fill_seq_with_data(Relation rel, HeapTuple tuple, bool create);
 static Relation lock_and_open_sequence(SeqTable seq);
 static void create_seq_hashtable(void);
 static void init_sequence(Oid relid, SeqTable *p_elm, Relation *p_rel);
@@ -222,7 +222,7 @@ DefineSequence(ParseState *pstate, CreateSeqStmt *seq)
 
 	/* now initialize the sequence's data */
 	tuple = heap_form_tuple(tupDesc, value, null);
-	fill_seq_with_data(rel, tuple);
+	fill_seq_with_data(rel, tuple, true);
 
 	/* process OWNED BY if given */
 	if (owned_by)
@@ -327,7 +327,7 @@ ResetSequence(Oid seq_relid)
 	/*
 	 * Insert the modified tuple into the new storage file.
 	 */
-	fill_seq_with_data(seq_rel, tuple);
+	fill_seq_with_data(seq_rel, tuple, true);
 
 	/* Clear local cache so that we don't think we have cached numbers */
 	/* Note that we do not change the currval() state */
@@ -340,7 +340,7 @@ ResetSequence(Oid seq_relid)
  * Initialize a sequence's relation with the specified tuple as content
  */
 static void
-fill_seq_with_data(Relation rel, HeapTuple tuple)
+fill_seq_with_data(Relation rel, HeapTuple tuple, bool create)
 {
 	Buffer		buf;
 	Page		page;
@@ -378,8 +378,31 @@ fill_seq_with_data(Relation rel, HeapTuple tuple)
 
 	/* check the comment above nextval_internal()'s equivalent call. */
 	if (RelationNeedsWAL(rel))
+	{
 		GetTopTransactionId();
 
+		/*
+		 * Ensure we have a proper XID, which will be included in the XLOG
+		 * record by XLogRecordAssemble. Otherwise the first nextval() in
+		 * a subxact (without any preceding changes) would get XID 0,
+		 * and it'd be impossible to decide which top xact it belongs to.
+		 * It'd also trigger assert in DecodeSequence.
+		 *
+		 * XXX This might seem unnecessary, because if there's no XID the
+		 * transaction couldn't have done anything important yet, e.g. it
+		 * could not have created a sequence. But that's incorrect, as it
+		 * ignores subtransactions. The current subtransaction might not
+		 * have done anything yet (thus no XID), but an earlier one might
+		 * have created the sequence.
+		 *
+		 * XXX Not sure if this is the best solution. Maybe do this only
+		 * with wal_level=logical to minimize the overhead. OTOH advancing
+		 * the sequence is likely followed by using the value(s) for some
+		 * other activity, which assigns the XID.
+		 */
+		GetCurrentTransactionId();
+	}
+
 	START_CRIT_SECTION();
 
 	MarkBufferDirty(buf);
@@ -399,6 +422,7 @@ fill_seq_with_data(Relation rel, HeapTuple tuple)
 		XLogRegisterBuffer(0, buf, REGBUF_WILL_INIT);
 
 		xlrec.node = rel->rd_node;
+		xlrec.created = create;
 
 		XLogRegisterData((char *) &xlrec, sizeof(xl_seq_rec));
 		XLogRegisterData((char *) tuple->t_data, tuple->t_len);
@@ -502,7 +526,7 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
 		/*
 		 * Insert the modified tuple into the new storage file.
 		 */
-		fill_seq_with_data(seqrel, newdatatuple);
+		fill_seq_with_data(seqrel, newdatatuple, true);
 	}
 
 	/* process OWNED BY if given */
@@ -766,8 +790,31 @@ nextval_internal(Oid relid, bool check_permissions)
 	 * (Have to do that here, so we're outside the critical section)
 	 */
 	if (logit && RelationNeedsWAL(seqrel))
+	{
 		GetTopTransactionId();
 
+		/*
+		 * Ensure we have a proper XID, which will be included in the XLOG
+		 * record by XLogRecordAssemble. Otherwise the first nextval() in
+		 * a subxact (without any preceding changes) would get XID 0,
+		 * and it'd be impossible to decide which top xact it belongs to.
+		 * It'd also trigger assert in DecodeSequence.
+		 *
+		 * XXX This might seem unnecessary, because if there's no XID the
+		 * transaction couldn't have done anything important yet, e.g. it
+		 * could not have created a sequence. But that's incorrect, as it
+		 * ignores subtransactions. The current subtransaction might not
+		 * have done anything yet (thus no XID), but an earlier one might
+		 * have created the sequence.
+		 *
+		 * XXX Not sure if this is the best solution. Maybe do this only
+		 * with wal_level=logical to minimize the overhead. OTOH advancing
+		 * the sequence is likely followed by using the value(s) for some
+		 * other activity, which assigns the XID.
+		 */
+		GetCurrentTransactionId();
+	}
+
 	/* ready to change the on-disk (or really, in-buffer) tuple */
 	START_CRIT_SECTION();
 
@@ -803,6 +850,7 @@ nextval_internal(Oid relid, bool check_permissions)
 		seq->log_cnt = 0;
 
 		xlrec.node = seqrel->rd_node;
+		xlrec.created = false;
 
 		XLogRegisterData((char *) &xlrec, sizeof(xl_seq_rec));
 		XLogRegisterData((char *) seqdatatuple.t_data, seqdatatuple.t_len);
@@ -977,8 +1025,31 @@ do_setval(Oid relid, int64 next, bool iscalled)
 
 	/* check the comment above nextval_internal()'s equivalent call. */
 	if (RelationNeedsWAL(seqrel))
+	{
 		GetTopTransactionId();
 
+		/*
+		 * Ensure we have a proper XID, which will be included in the XLOG
+		 * record by XLogRecordAssemble. Otherwise the first nextval() in
+		 * a subxact (without any preceding changes) would get XID 0,
+		 * and it'd be impossible to decide which top xact it belongs to.
+		 * It'd also trigger assert in DecodeSequence.
+		 *
+		 * XXX This might seem unnecessary, because if there's no XID the
+		 * transaction couldn't have done anything important yet, e.g. it
+		 * could not have created a sequence. But that's incorrect, as it
+		 * ignores subtransactions. The current subtransaction might not
+		 * have done anything yet (thus no XID), but an earlier one might
+		 * have created the sequence.
+		 *
+		 * XXX Not sure if this is the best solution. Maybe do this only
+		 * with wal_level=logical to minimize the overhead. OTOH advancing
+		 * the sequence is likely followed by using the value(s) for some
+		 * other activity, which assigns the XID.
+		 */
+		GetCurrentTransactionId();
+	}
+
 	/* ready to change the on-disk (or really, in-buffer) tuple */
 	START_CRIT_SECTION();
 
@@ -999,6 +1070,8 @@ do_setval(Oid relid, int64 next, bool iscalled)
 		XLogRegisterBuffer(0, buf, REGBUF_WILL_INIT);
 
 		xlrec.node = seqrel->rd_node;
+		xlrec.created = false;
+
 		XLogRegisterData((char *) &xlrec, sizeof(xl_seq_rec));
 		XLogRegisterData((char *) seqdatatuple.t_data, seqdatatuple.t_len);
 
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index a2b69511b4..b61f2e264a 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -42,6 +42,7 @@
 #include "replication/reorderbuffer.h"
 #include "replication/snapbuild.h"
 #include "storage/standby.h"
+#include "commands/sequence.h"
 
 typedef struct XLogRecordBuffer
 {
@@ -74,10 +75,11 @@ static void DecodeAbort(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 						bool two_phase);
 static void DecodePrepare(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 						  xl_xact_parsed_prepare *parsed);
-
+static void DecodeSequence(LogicalDecodingContext *ctx, XLogRecordBuffer *buf);
 
 /* common function to decode tuples */
 static void DecodeXLogTuple(char *data, Size len, ReorderBufferTupleBuf *tup);
+static void DecodeSeqTuple(char *data, Size len, ReorderBufferTupleBuf *tuple);
 
 /* helper functions for decoding transactions */
 static inline bool FilterPrepare(LogicalDecodingContext *ctx,
@@ -158,6 +160,10 @@ LogicalDecodingProcessRecord(LogicalDecodingContext *ctx, XLogReaderState *recor
 			DecodeLogicalMsgOp(ctx, &buf);
 			break;
 
+		case RM_SEQ_ID:
+			DecodeSequence(ctx, &buf);
+			break;
+
 			/*
 			 * Rmgrs irrelevant for logical decoding; they describe stuff not
 			 * represented in logical decoding. Add new rmgrs in rmgrlist.h's
@@ -173,7 +179,6 @@ LogicalDecodingProcessRecord(LogicalDecodingContext *ctx, XLogReaderState *recor
 		case RM_HASH_ID:
 		case RM_GIN_ID:
 		case RM_GIST_ID:
-		case RM_SEQ_ID:
 		case RM_SPGIST_ID:
 		case RM_BRIN_ID:
 		case RM_COMMIT_TS_ID:
@@ -1313,3 +1318,125 @@ DecodeTXNNeedSkip(LogicalDecodingContext *ctx, XLogRecordBuffer *buf,
 			(txn_dbid != InvalidOid && txn_dbid != ctx->slot->data.database) ||
 			ctx->fast_forward || FilterByOrigin(ctx, origin_id));
 }
+
+/*
+ * Decode Sequence Tuple
+ */
+static void
+DecodeSeqTuple(char *data, Size len, ReorderBufferTupleBuf *tuple)
+{
+	int			datalen = len - sizeof(xl_seq_rec) - SizeofHeapTupleHeader;
+
+	Assert(datalen >= 0);
+
+	tuple->tuple.t_len = datalen + SizeofHeapTupleHeader;;
+
+	ItemPointerSetInvalid(&tuple->tuple.t_self);
+
+	tuple->tuple.t_tableOid = InvalidOid;
+
+	memcpy(((char *) tuple->tuple.t_data),
+		   data + sizeof(xl_seq_rec),
+		   SizeofHeapTupleHeader);
+
+	memcpy(((char *) tuple->tuple.t_data) + SizeofHeapTupleHeader,
+		   data + sizeof(xl_seq_rec) + SizeofHeapTupleHeader,
+		   datalen);
+}
+
+/*
+ * Handle sequence decode
+ *
+ * Decoding sequences is a bit tricky, because while most sequence actions
+ * are non-transactional (not subject to rollback), some need to be handled
+ * as transactional.
+ *
+ * By default, a sequence increment is non-transactional - we must not queue
+ * it in a transaction as other changes, because the transaction might get
+ * rolled back and we'd discard the increment. The downstream would not be
+ * notified about the increment, which is wrong.
+ *
+ * On the other hand, the sequence may be created in a transaction. In this
+ * case we *should* queue the change as other changes in the transaction,
+ * because we don't want to send the increments for unknown sequence to the
+ * plugin - it might get confused about which sequence it's related to etc.
+ */
+static void
+DecodeSequence(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
+{
+	SnapBuild  *builder = ctx->snapshot_builder;
+	ReorderBufferTupleBuf *tuplebuf;
+	RelFileNode target_node;
+	XLogReaderState *r = buf->record;
+	char	   *tupledata = NULL;
+	Size		tuplelen;
+	Size		datalen = 0;
+	TransactionId xid = XLogRecGetXid(r);
+	uint8		info = XLogRecGetInfo(buf->record) & ~XLR_INFO_MASK;
+	xl_seq_rec *xlrec;
+	Snapshot	snapshot;
+	RepOriginId origin_id = XLogRecGetOrigin(r);
+	bool		transactional;
+
+	/* only decode changes flagged with XLOG_SEQ_LOG */
+	if (info != XLOG_SEQ_LOG)
+		elog(ERROR, "unexpected RM_SEQ_ID record type: %u", info);
+
+	/*
+	 * If we don't have snapshot or we are just fast-forwarding, there is no
+	 * point in decoding messages.
+	 */
+	if (SnapBuildCurrentState(builder) < SNAPBUILD_FULL_SNAPSHOT ||
+		ctx->fast_forward)
+		return;
+
+	/* only interested in our database */
+	XLogRecGetBlockTag(r, 0, &target_node, NULL, NULL);
+	if (target_node.dbNode != ctx->slot->data.database)
+		return;
+
+	/* output plugin doesn't look for this origin, no need to queue */
+	if (FilterByOrigin(ctx, XLogRecGetOrigin(r)))
+		return;
+
+	tupledata = XLogRecGetData(r);
+	datalen = XLogRecGetDataLen(r);
+	tuplelen = datalen - SizeOfHeapHeader - sizeof(xl_seq_rec);
+
+	/* extract the WAL record, with "created" flag */
+	xlrec = (xl_seq_rec *) XLogRecGetData(r);
+
+	/* XXX how could we have sequence change without data? */
+	if(!datalen || !tupledata)
+		return;
+
+	tuplebuf = ReorderBufferGetTupleBuf(ctx->reorder, tuplelen);
+	DecodeSeqTuple(tupledata, datalen, tuplebuf);
+
+	/*
+	 * Should we handle the sequence increment as transactional or not?
+	 *
+	 * If the sequence was created in a still-running transaction, treat
+	 * it as transactional and queue the increments. Otherwise it needs
+	 * to be treated as non-transactional, in which case we send it to
+	 * the plugin right away.
+	 */
+	transactional = ReorderBufferSequenceIsTransactional(ctx->reorder,
+														 target_node,
+														 xlrec->created);
+
+	/* Skip the change if already processed (per the snapshot). */
+	if (transactional &&
+		!SnapBuildProcessChange(builder, xid, buf->origptr))
+		return;
+	else if (!transactional &&
+			 (SnapBuildCurrentState(builder) != SNAPBUILD_CONSISTENT ||
+			  SnapBuildXactNeedsSkip(builder, buf->origptr)))
+		return;
+
+	/* Queue the increment (or send immediately if not transactional). */
+	snapshot = SnapBuildGetOrBuildSnapshot(builder, xid);
+	ReorderBufferQueueSequence(ctx->reorder, xid, snapshot, buf->endptr,
+							   origin_id, target_node, transactional,
+							   xlrec->created, tuplebuf);
+}
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c
index b7d9521576..811d9912a1 100644
--- a/src/backend/replication/logical/logical.c
+++ b/src/backend/replication/logical/logical.c
@@ -73,6 +73,10 @@ static void truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
 static void message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
 							   XLogRecPtr message_lsn, bool transactional,
 							   const char *prefix, Size message_size, const char *message);
+static void sequence_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+								XLogRecPtr sequence_lsn, Relation rel,
+								bool transactional, bool created,
+								int64 last_value, int64 log_cnt, bool is_called);
 
 /* streaming callbacks */
 static void stream_start_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
@@ -90,6 +94,10 @@ static void stream_change_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn
 static void stream_message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
 									  XLogRecPtr message_lsn, bool transactional,
 									  const char *prefix, Size message_size, const char *message);
+static void stream_sequence_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+									   XLogRecPtr sequence_lsn, Relation rel,
+									   bool transactional, bool created,
+									   int64 last_value, int64 log_cnt, bool is_called);
 static void stream_truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
 									   int nrelations, Relation relations[], ReorderBufferChange *change);
 
@@ -217,6 +225,7 @@ StartupDecodingContext(List *output_plugin_options,
 	ctx->reorder->apply_truncate = truncate_cb_wrapper;
 	ctx->reorder->commit = commit_cb_wrapper;
 	ctx->reorder->message = message_cb_wrapper;
+	ctx->reorder->sequence = sequence_cb_wrapper;
 
 	/*
 	 * To support streaming, we require start/stop/abort/commit/change
@@ -233,6 +242,7 @@ StartupDecodingContext(List *output_plugin_options,
 		(ctx->callbacks.stream_commit_cb != NULL) ||
 		(ctx->callbacks.stream_change_cb != NULL) ||
 		(ctx->callbacks.stream_message_cb != NULL) ||
+		(ctx->callbacks.stream_sequence_cb != NULL) ||
 		(ctx->callbacks.stream_truncate_cb != NULL);
 
 	/*
@@ -250,6 +260,7 @@ StartupDecodingContext(List *output_plugin_options,
 	ctx->reorder->stream_commit = stream_commit_cb_wrapper;
 	ctx->reorder->stream_change = stream_change_cb_wrapper;
 	ctx->reorder->stream_message = stream_message_cb_wrapper;
+	ctx->reorder->stream_sequence = stream_sequence_cb_wrapper;
 	ctx->reorder->stream_truncate = stream_truncate_cb_wrapper;
 
 
@@ -1202,6 +1213,43 @@ message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
 	error_context_stack = errcallback.previous;
 }
 
+static void
+sequence_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+					XLogRecPtr sequence_lsn, Relation rel,
+					bool transactional, bool created,
+					int64 last_value, int64 log_cnt, bool is_called)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	if (ctx->callbacks.sequence_cb == NULL)
+		return;
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "sequence";
+	state.report_location = sequence_lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
+	ctx->write_location = sequence_lsn;
+
+	/* do the actual work: call callback */
+	ctx->callbacks.sequence_cb(ctx, txn, sequence_lsn, rel, transactional,
+							   created, last_value, log_cnt, is_called);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
 static void
 stream_start_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
 						XLogRecPtr first_lsn)
@@ -1507,6 +1555,47 @@ stream_message_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
 	error_context_stack = errcallback.previous;
 }
 
+static void
+stream_sequence_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
+						   XLogRecPtr sequence_lsn, Relation rel,
+						   bool transactional, bool created,
+						   int64 last_value, int64 log_cnt, bool is_called)
+{
+	LogicalDecodingContext *ctx = cache->private_data;
+	LogicalErrorCallbackState state;
+	ErrorContextCallback errcallback;
+
+	Assert(!ctx->fast_forward);
+
+	/* We're only supposed to call this when streaming is supported. */
+	Assert(ctx->streaming);
+
+	/* this callback is optional */
+	if (ctx->callbacks.stream_sequence_cb == NULL)
+		return;
+
+	/* Push callback + info on the error context stack */
+	state.ctx = ctx;
+	state.callback_name = "stream_sequence";
+	state.report_location = sequence_lsn;
+	errcallback.callback = output_plugin_error_callback;
+	errcallback.arg = (void *) &state;
+	errcallback.previous = error_context_stack;
+	error_context_stack = &errcallback;
+
+	/* set output state */
+	ctx->accept_writes = true;
+	ctx->write_xid = txn != NULL ? txn->xid : InvalidTransactionId;
+	ctx->write_location = sequence_lsn;
+
+	/* do the actual work: call callback */
+	ctx->callbacks.sequence_cb(ctx, txn, sequence_lsn, rel, transactional,
+							   created, last_value, log_cnt, is_called);
+
+	/* Pop the error context stack */
+	error_context_stack = errcallback.previous;
+}
+
 static void
 stream_truncate_cb_wrapper(ReorderBuffer *cache, ReorderBufferTXN *txn,
 						   int nrelations, Relation relations[],
diff --git a/src/backend/replication/logical/reorderbuffer.c b/src/backend/replication/logical/reorderbuffer.c
index 46e66608cf..434926459f 100644
--- a/src/backend/replication/logical/reorderbuffer.c
+++ b/src/backend/replication/logical/reorderbuffer.c
@@ -77,6 +77,35 @@
  *	  a bit more memory to the oldest subtransactions, because it's likely
  *	  they are the source for the next sequence of changes.
  *
+ *	  When decoding sequences, we differentiate between a sequences created
+ *	  in a (running) transaction, and sequences created in other (already
+ *	  committed) transactions. Changes for sequences created in the same
+ *	  top-level transaction are treated as "transactional" i.e. just like
+ *	  any other change from that transaction (and discarded in case of a
+ *	  rollback). Changes for sequences created earlier are treated as not
+ *	  transactional - are processed immediately, as if performed outside
+ *	  any transaction (and thus not rolled back).
+ *
+ *	  This mixed behavior is necessary - sequences are non-transactional
+ *	  (e.g. ROLLBACK does not undo the sequence increments). But for new
+ *	  sequences, we need to handle them in a transactional way, because if
+ *	  we ever get some DDL support, the sequence won't exist until the
+ *	  transaction gets applied. So we need to ensure the increments don't
+ *	  happen until the sequence gets created.
+ *
+ *	  To differentiate which sequences are "old" and which were created
+ *	  in a still-running transaction, we track sequences created in running
+ *	  transactions in a hash table. Each sequence is identified by it's
+ *	  relfilenode, and at transaction commit we discard all sequences
+ *	  created in that particular transaction. For each sequence we track
+ *	  the XID of the (sub)transaction that created it, and we cleanup the
+ *	  sequences for each subtransaction when it completes (commit/rollback).
+ *
+ *	  We don't use the XID to check if it's the same top-level transaction.
+ *	  It's enough to know it was created in an in-progress transaction,
+ *	  and we know it must be the current one because otherwise it wouldn't
+ *	  see the sequence object.
+ *
  * -------------------------------------------------------------------------
  */
 #include "postgres.h"
@@ -116,6 +145,13 @@ typedef struct ReorderBufferTXNByIdEnt
 	ReorderBufferTXN *txn;
 } ReorderBufferTXNByIdEnt;
 
+/* entry for hash table we use to track sequences created in running xacts */
+typedef struct ReorderBufferSequenceEnt
+{
+	RelFileNode		rnode;
+	TransactionId	xid;
+} ReorderBufferSequenceEnt;
+
 /* data structures for (relfilenode, ctid) => (cmin, cmax) mapping */
 typedef struct ReorderBufferTupleCidKey
 {
@@ -339,6 +375,14 @@ ReorderBufferAllocate(void)
 	buffer->by_txn = hash_create("ReorderBufferByXid", 1000, &hash_ctl,
 								 HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
 
+	/* hash table of sequences, mapping relfilenode to XID of transaction */
+	hash_ctl.keysize = sizeof(RelFileNode);
+	hash_ctl.entrysize = sizeof(ReorderBufferSequenceEnt);
+	hash_ctl.hcxt = buffer->context;
+
+	buffer->sequences = hash_create("ReorderBufferSequenceHash", 1000, &hash_ctl,
+								 HASH_ELEM | HASH_BLOBS | HASH_CONTEXT);
+
 	buffer->by_txn_last_xid = InvalidTransactionId;
 	buffer->by_txn_last_txn = NULL;
 
@@ -525,6 +569,13 @@ ReorderBufferReturnChange(ReorderBuffer *rb, ReorderBufferChange *change,
 				change->data.truncate.relids = NULL;
 			}
 			break;
+		case REORDER_BUFFER_CHANGE_SEQUENCE:
+			if (change->data.sequence.tuple)
+			{
+				ReorderBufferReturnTupleBuf(rb, change->data.sequence.tuple);
+				change->data.sequence.tuple = NULL;
+			}
+			break;
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT:
 		case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
@@ -859,6 +910,242 @@ ReorderBufferQueueMessage(ReorderBuffer *rb, TransactionId xid,
 	}
 }
 
+/*
+ * Treat the sequence increment as transactional?
+ *
+ * The hash table tracks all sequences created in in-progress transactions,
+ * so we simply do a lookup (the sequence is identified by relfilende). If
+ * we find a match, the increment should be handled as transactional.
+ */
+bool
+ReorderBufferSequenceIsTransactional(ReorderBuffer *rb,
+									 RelFileNode rnode, bool created)
+{
+	bool	found = false;
+
+	if (created)
+		return true;
+
+	hash_search(rb->sequences,
+				(void *) &rnode,
+				HASH_FIND,
+				&found);
+
+	return found;
+}
+
+/*
+ * Cleanup sequences created in in-progress transactions.
+ *
+ * There's no way to search by XID, so we simply do a seqscan of all
+ * the entries in the hash table. Hopefully there are only a couple
+ * entries in most cases - people generally don't create many new
+ * sequences over and over.
+ */
+static void
+ReorderBufferSequenceCleanup(ReorderBuffer *rb, TransactionId xid)
+{
+	HASH_SEQ_STATUS scan_status;
+	ReorderBufferSequenceEnt *ent;
+
+	hash_seq_init(&scan_status, rb->sequences);
+	while ((ent = (ReorderBufferSequenceEnt *) hash_seq_search(&scan_status)) != NULL)
+	{
+		/* skip sequences not from this transaction */
+		if (ent->xid != xid)
+			continue;
+
+		(void) hash_search(rb->sequences,
+					   (void *) &(ent->rnode),
+					   HASH_REMOVE, NULL);
+	}
+}
+
+/*
+ * A transactional sequence increment is queued to be processed upon commit
+ * and a non-transactional increment gets processed immediately.
+ *
+ * A sequence update may be both transactional and non-transactional. When
+ * created in a running transaction, treat it as transactional and queue
+ * the change in it. Otherwise treat it as non-transactional, so that we
+ * don't forget the increment in case of a rollback.
+ */
+void
+ReorderBufferQueueSequence(ReorderBuffer *rb, TransactionId xid,
+						   Snapshot snapshot, XLogRecPtr lsn, RepOriginId origin_id,
+						   RelFileNode rnode, bool transactional, bool created,
+						   ReorderBufferTupleBuf *tuplebuf)
+{
+	/*
+	 * Change needs to be handled as transactional, because the sequence was
+	 * created in a transaction that is still running. In that case all the
+	 * changes need to be queued in that transaction, we must not send them
+	 * to the downstream until the transaction commits.
+	 *
+	 * There's a bit of a trouble with subtransactions - we can't queue it
+	 * into the subxact, because it might be rolled back and we'd lose the
+	 * increment. We need to queue it into the same (sub)xact that created
+	 * the sequence, which is why we track the XID in the hash table.
+	 */
+	if (transactional)
+	{
+		MemoryContext oldcontext;
+		ReorderBufferChange *change;
+
+		/* lookup sequence by relfilenode */
+		ReorderBufferSequenceEnt   *ent;
+		bool						found;
+
+		/* transactional changes require a transaction */
+		Assert(xid != InvalidTransactionId);
+
+		/* search the lookup table (we ignore the return value, found is enough) */
+		ent = hash_search(rb->sequences,
+						  (void *) &rnode,
+						  created ? HASH_ENTER : HASH_FIND,
+						  &found);
+
+		/*
+		 * If this is the "create" increment, we must not have found any
+		 * pre-existing entry in the hash table (i.e. there must not be
+		 * any conflicting sequence).
+		 */
+		Assert(!(created && found));
+
+		/* But we must have either created or found an existing entry. */
+		Assert(created || found);
+
+		/*
+		 * When creating the sequence, remember the XID of the transaction
+		 * that created id.
+		 */
+		if (created)
+			ent->xid = xid;
+
+		/* XXX Maybe check that we're still in the same top-level xact? */
+
+		/* OK, allocate and queue the change */
+		oldcontext = MemoryContextSwitchTo(rb->context);
+
+		change = ReorderBufferGetChange(rb);
+
+		change->action = REORDER_BUFFER_CHANGE_SEQUENCE;
+		change->origin_id = origin_id;
+
+		memcpy(&change->data.sequence.relnode, &rnode, sizeof(RelFileNode));
+
+		change->data.sequence.created = created;
+		change->data.sequence.tuple = tuplebuf;
+
+		/* add it to the same subxact that created the sequence */
+		ReorderBufferQueueChange(rb, ent->xid, lsn, change, false);
+
+		MemoryContextSwitchTo(oldcontext);
+	}
+	else
+	{
+		/*
+		 * This increment is for a sequence that was not created in any
+		 * running transaction, so we treat it as non-transactional and
+		 * just send it to the output plugin directly.
+		 */
+		ReorderBufferTXN *txn = NULL;
+		volatile Snapshot snapshot_now = snapshot;
+		bool	using_subtxn;
+
+#ifdef USE_ASSERT_CHECKING
+		/* All "creates" have to be handled as transactional. */
+		Assert(!created);
+
+		/* Make sure the sequence is not in the hash table. */
+		{
+			bool	found;
+			hash_search(rb->sequences,
+						(void *) &rnode,
+						HASH_FIND, &found);
+			Assert(!found);
+		}
+#endif
+
+		if (xid != InvalidTransactionId)
+			txn = ReorderBufferTXNByXid(rb, xid, true, NULL, lsn, true);
+
+		/* setup snapshot to allow catalog access */
+		SetupHistoricSnapshot(snapshot_now, NULL);
+
+		/*
+		 * Decoding needs access to syscaches et al., which in turn use
+		 * heavyweight locks and such. Thus we need to have enough state around to
+		 * keep track of those.  The easiest way is to simply use a transaction
+		 * internally.  That also allows us to easily enforce that nothing writes
+		 * to the database by checking for xid assignments.
+		 *
+		 * When we're called via the SQL SRF there's already a transaction
+		 * started, so start an explicit subtransaction there.
+		 */
+		using_subtxn = IsTransactionOrTransactionBlock();
+
+		PG_TRY();
+		{
+			Relation	relation;
+			HeapTuple	tuple;
+			bool		isnull;
+			int64		last_value, log_cnt;
+			bool		is_called;
+			Oid			reloid;
+
+			if (using_subtxn)
+				BeginInternalSubTransaction("sequence");
+			else
+				StartTransactionCommand();
+
+			reloid = RelidByRelfilenode(rnode.spcNode, rnode.relNode);
+
+			if (reloid == InvalidOid)
+				elog(ERROR, "could not map filenode \"%s\" to relation OID",
+					 relpathperm(rnode,
+								 MAIN_FORKNUM));
+
+			relation = RelationIdGetRelation(reloid);
+			tuple = &tuplebuf->tuple;
+
+			/*
+			 * Extract the internal sequence values, describing the state.
+			 *
+			 * XXX Seems a bit strange to access it directly. Maybe there's
+			 * a better / more correct way?
+			 */
+			last_value = heap_getattr(tuple, 1, RelationGetDescr(relation), &isnull);
+			log_cnt = heap_getattr(tuple, 2, RelationGetDescr(relation), &isnull);
+			is_called = heap_getattr(tuple, 3, RelationGetDescr(relation), &isnull);
+
+			rb->sequence(rb, txn, lsn, relation, transactional, created,
+						 last_value, log_cnt, is_called);
+
+			RelationClose(relation);
+
+			TeardownHistoricSnapshot(false);
+
+			AbortCurrentTransaction();
+
+			if (using_subtxn)
+				RollbackAndReleaseCurrentSubTransaction();
+		}
+		PG_CATCH();
+		{
+			TeardownHistoricSnapshot(true);
+
+			AbortCurrentTransaction();
+
+			if (using_subtxn)
+				RollbackAndReleaseCurrentSubTransaction();
+
+			PG_RE_THROW();
+		}
+		PG_END_TRY();
+	}
+}
+
 /*
  * AssertTXNLsnOrder
  *		Verify LSN ordering of transaction lists in the reorderbuffer
@@ -1535,6 +1822,9 @@ ReorderBufferCleanupTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
 				&found);
 	Assert(found);
 
+	/* Remove sequences created in this transaction (if any). */
+	ReorderBufferSequenceCleanup(rb, txn->xid);
+
 	/* remove entries spilled to disk */
 	if (rbtxn_is_serialized(txn))
 		ReorderBufferRestoreCleanup(rb, txn);
@@ -1950,6 +2240,42 @@ ReorderBufferApplyMessage(ReorderBuffer *rb, ReorderBufferTXN *txn,
 					change->data.msg.message);
 }
 
+/*
+ * Helper function for ReorderBufferProcessTXN for applying sequences.
+ */
+static inline void
+ReorderBufferApplySequence(ReorderBuffer *rb, ReorderBufferTXN *txn,
+						   Relation relation, ReorderBufferChange *change,
+						   bool streaming)
+{
+	HeapTuple	tuple;
+	bool		isnull;
+	int64		last_value, log_cnt;
+	bool		is_called;
+
+	tuple = &change->data.sequence.tuple->tuple;
+
+	/*
+	 * Extract the internal sequence values, describing the state.
+	 *
+	 * XXX Seems a bit strange to access it directly. Maybe there's
+	 * a better / more correct way?
+	 */
+	last_value = heap_getattr(tuple, 1, RelationGetDescr(relation), &isnull);
+	log_cnt = heap_getattr(tuple, 2, RelationGetDescr(relation), &isnull);
+	is_called = heap_getattr(tuple, 3, RelationGetDescr(relation), &isnull);
+
+	/* Only ever called from ReorderBufferApplySequence, so transational. */
+	if (streaming)
+		rb->stream_sequence(rb, txn, change->lsn, relation, true,
+							change->data.sequence.created,
+							last_value, log_cnt, is_called);
+	else
+		rb->sequence(rb, txn, change->lsn, relation, true,
+					 change->data.sequence.created,
+					 last_value, log_cnt, is_called);
+}
+
 /*
  * Function to store the command id and snapshot at the end of the current
  * stream so that we can reuse the same while sending the next stream.
@@ -2392,6 +2718,31 @@ ReorderBufferProcessTXN(ReorderBuffer *rb, ReorderBufferTXN *txn,
 				case REORDER_BUFFER_CHANGE_INTERNAL_TUPLECID:
 					elog(ERROR, "tuplecid value in changequeue");
 					break;
+
+				case REORDER_BUFFER_CHANGE_SEQUENCE:
+					Assert(snapshot_now);
+
+					reloid = RelidByRelfilenode(change->data.sequence.relnode.spcNode,
+												change->data.sequence.relnode.relNode);
+
+					if (reloid == InvalidOid)
+						elog(ERROR, "could not map filenode \"%s\" to relation OID",
+							 relpathperm(change->data.sequence.relnode,
+										 MAIN_FORKNUM));
+
+					relation = RelationIdGetRelation(reloid);
+
+					if (!RelationIsValid(relation))
+						elog(ERROR, "could not open relation with OID %u (for filenode \"%s\")",
+							 reloid,
+							 relpathperm(change->data.sequence.relnode,
+										 MAIN_FORKNUM));
+
+					if (RelationIsLogicallyLogged(relation))
+						ReorderBufferApplySequence(rb, txn, relation, change, streaming);
+
+					RelationClose(relation);
+					break;
 			}
 		}
 
@@ -3776,6 +4127,39 @@ ReorderBufferSerializeChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
 				memcpy(data, change->data.truncate.relids, size);
 				data += size;
 
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_SEQUENCE:
+			{
+				char	   *data;
+				ReorderBufferTupleBuf *tup;
+				Size		len = 0;
+
+				tup = change->data.sequence.tuple;
+
+				if (tup)
+				{
+					sz += sizeof(HeapTupleData);
+					len = tup->tuple.t_len;
+					sz += len;
+				}
+
+				/* make sure we have enough space */
+				ReorderBufferSerializeReserve(rb, sz);
+
+				data = ((char *) rb->outbuf) + sizeof(ReorderBufferDiskChange);
+				/* might have been reallocated above */
+				ondisk = (ReorderBufferDiskChange *) rb->outbuf;
+
+				if (len)
+				{
+					memcpy(data, &tup->tuple, sizeof(HeapTupleData));
+					data += sizeof(HeapTupleData);
+
+					memcpy(data, tup->tuple.t_data, len);
+					data += len;
+				}
+
 				break;
 			}
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
@@ -4040,6 +4424,22 @@ ReorderBufferChangeSize(ReorderBufferChange *change)
 			{
 				sz += sizeof(Oid) * change->data.truncate.nrelids;
 
+				break;
+			}
+		case REORDER_BUFFER_CHANGE_SEQUENCE:
+			{
+				ReorderBufferTupleBuf *tup;
+				Size		len = 0;
+
+				tup = change->data.sequence.tuple;
+
+				if (tup)
+				{
+					sz += sizeof(HeapTupleData);
+					len = tup->tuple.t_len;
+					sz += len;
+				}
+
 				break;
 			}
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
@@ -4341,6 +4741,30 @@ ReorderBufferRestoreChange(ReorderBuffer *rb, ReorderBufferTXN *txn,
 
 				break;
 			}
+
+		case REORDER_BUFFER_CHANGE_SEQUENCE:
+			if (change->data.sequence.tuple)
+			{
+				uint32		tuplelen = ((HeapTuple) data)->t_len;
+
+				change->data.sequence.tuple =
+					ReorderBufferGetTupleBuf(rb, tuplelen - SizeofHeapTupleHeader);
+
+				/* restore ->tuple */
+				memcpy(&change->data.sequence.tuple->tuple, data,
+					   sizeof(HeapTupleData));
+				data += sizeof(HeapTupleData);
+
+				/* reset t_data pointer into the new tuplebuf */
+				change->data.sequence.tuple->tuple.t_data =
+					ReorderBufferTupleBufData(change->data.sequence.tuple);
+
+				/* restore tuple data itself */
+				memcpy(change->data.sequence.tuple->tuple.t_data, data, tuplelen);
+				data += tuplelen;
+			}
+			break;
+
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM:
 		case REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT:
 		case REORDER_BUFFER_CHANGE_INTERNAL_COMMAND_ID:
diff --git a/src/include/commands/sequence.h b/src/include/commands/sequence.h
index 40544dd4c7..5919fb90ee 100644
--- a/src/include/commands/sequence.h
+++ b/src/include/commands/sequence.h
@@ -48,6 +48,7 @@ typedef FormData_pg_sequence_data *Form_pg_sequence_data;
 typedef struct xl_seq_rec
 {
 	RelFileNode node;
+	bool		created;	/* is this a CREATE SEQUENCE */
 	/* SEQUENCE TUPLE DATA FOLLOWS AT THE END */
 } xl_seq_rec;
 
diff --git a/src/include/replication/output_plugin.h b/src/include/replication/output_plugin.h
index 810495ed0e..57bc13f11c 100644
--- a/src/include/replication/output_plugin.h
+++ b/src/include/replication/output_plugin.h
@@ -88,6 +88,19 @@ typedef void (*LogicalDecodeMessageCB) (struct LogicalDecodingContext *ctx,
 										Size message_size,
 										const char *message);
 
+/*
+ * Called for the generic logical decoding sequences.
+ */
+typedef void (*LogicalDecodeSequenceCB) (struct LogicalDecodingContext *ctx,
+										 ReorderBufferTXN *txn,
+										 XLogRecPtr sequence_lsn,
+										 Relation rel,
+										 bool transactional,
+										 bool created,
+										 int64 last_value,
+										 int64 log_cnt,
+										 bool is_called);
+
 /*
  * Filter changes by origin.
  */
@@ -199,6 +212,20 @@ typedef void (*LogicalDecodeStreamMessageCB) (struct LogicalDecodingContext *ctx
 											  Size message_size,
 											  const char *message);
 
+/*
+ * Called for the streaming generic logical decoding sequences from in-progress
+ * transactions.
+ */
+typedef void (*LogicalDecodeStreamSequenceCB) (struct LogicalDecodingContext *ctx,
+											   ReorderBufferTXN *txn,
+											   XLogRecPtr sequence_lsn,
+											   Relation rel,
+											   bool transactional,
+											   bool created,
+											   int64 last_value,
+											   int64 log_cnt,
+											   bool is_called);
+
 /*
  * Callback for streaming truncates from in-progress transactions.
  */
@@ -219,6 +246,7 @@ typedef struct OutputPluginCallbacks
 	LogicalDecodeTruncateCB truncate_cb;
 	LogicalDecodeCommitCB commit_cb;
 	LogicalDecodeMessageCB message_cb;
+	LogicalDecodeSequenceCB sequence_cb;
 	LogicalDecodeFilterByOriginCB filter_by_origin_cb;
 	LogicalDecodeShutdownCB shutdown_cb;
 
@@ -237,6 +265,7 @@ typedef struct OutputPluginCallbacks
 	LogicalDecodeStreamCommitCB stream_commit_cb;
 	LogicalDecodeStreamChangeCB stream_change_cb;
 	LogicalDecodeStreamMessageCB stream_message_cb;
+	LogicalDecodeStreamSequenceCB stream_sequence_cb;
 	LogicalDecodeStreamTruncateCB stream_truncate_cb;
 } OutputPluginCallbacks;
 
diff --git a/src/include/replication/reorderbuffer.h b/src/include/replication/reorderbuffer.h
index 5b40ff75f7..63e6ed037b 100644
--- a/src/include/replication/reorderbuffer.h
+++ b/src/include/replication/reorderbuffer.h
@@ -64,7 +64,8 @@ enum ReorderBufferChangeType
 	REORDER_BUFFER_CHANGE_INTERNAL_SPEC_INSERT,
 	REORDER_BUFFER_CHANGE_INTERNAL_SPEC_CONFIRM,
 	REORDER_BUFFER_CHANGE_INTERNAL_SPEC_ABORT,
-	REORDER_BUFFER_CHANGE_TRUNCATE
+	REORDER_BUFFER_CHANGE_TRUNCATE,
+	REORDER_BUFFER_CHANGE_SEQUENCE
 };
 
 /* forward declaration */
@@ -158,6 +159,14 @@ typedef struct ReorderBufferChange
 			uint32		ninvalidations; /* Number of messages */
 			SharedInvalidationMessage *invalidations;	/* invalidation message */
 		}			inval;
+
+		/* Context data for Sequence changes */
+		struct
+		{
+			RelFileNode relnode;
+			bool		created;
+			ReorderBufferTupleBuf *tuple;
+		}			sequence;
 	}			data;
 
 	/*
@@ -430,6 +439,15 @@ typedef void (*ReorderBufferMessageCB) (ReorderBuffer *rb,
 										const char *prefix, Size sz,
 										const char *message);
 
+/* sequence callback signature */
+typedef void (*ReorderBufferSequenceCB) (ReorderBuffer *rb,
+										 ReorderBufferTXN *txn,
+										 XLogRecPtr sequence_lsn,
+										 Relation rel,
+										 bool transactional, bool created,
+										 int64 last_value, int64 log_cnt,
+										 bool is_called);
+
 /* begin prepare callback signature */
 typedef void (*ReorderBufferBeginPrepareCB) (ReorderBuffer *rb,
 											 ReorderBufferTXN *txn);
@@ -496,6 +514,15 @@ typedef void (*ReorderBufferStreamMessageCB) (
 											  const char *prefix, Size sz,
 											  const char *message);
 
+/* stream sequence callback signature */
+typedef void (*ReorderBufferStreamSequenceCB) (ReorderBuffer *rb,
+											   ReorderBufferTXN *txn,
+											   XLogRecPtr sequence_lsn,
+											   Relation rel,
+											   bool transactional, bool created,
+											   int64 last_value, int64 log_cnt,
+											   bool is_called);
+
 /* stream truncate callback signature */
 typedef void (*ReorderBufferStreamTruncateCB) (
 											   ReorderBuffer *rb,
@@ -511,6 +538,12 @@ struct ReorderBuffer
 	 */
 	HTAB	   *by_txn;
 
+	/*
+	 * relfilenode => XID lookup table for sequences created in a transaction
+	 * (also includes altered sequences, which assigns new relfilenode)
+	 */
+	HTAB	   *sequences;
+
 	/*
 	 * Transactions that could be a toplevel xact, ordered by LSN of the first
 	 * record bearing that xid.
@@ -541,6 +574,7 @@ struct ReorderBuffer
 	ReorderBufferApplyTruncateCB apply_truncate;
 	ReorderBufferCommitCB commit;
 	ReorderBufferMessageCB message;
+	ReorderBufferSequenceCB sequence;
 
 	/*
 	 * Callbacks to be called when streaming a transaction at prepare time.
@@ -560,6 +594,7 @@ struct ReorderBuffer
 	ReorderBufferStreamCommitCB stream_commit;
 	ReorderBufferStreamChangeCB stream_change;
 	ReorderBufferStreamMessageCB stream_message;
+	ReorderBufferStreamSequenceCB stream_sequence;
 	ReorderBufferStreamTruncateCB stream_truncate;
 
 	/*
@@ -635,6 +670,10 @@ void		ReorderBufferQueueChange(ReorderBuffer *, TransactionId,
 void		ReorderBufferQueueMessage(ReorderBuffer *, TransactionId, Snapshot snapshot, XLogRecPtr lsn,
 									  bool transactional, const char *prefix,
 									  Size message_size, const char *message);
+void		ReorderBufferQueueSequence(ReorderBuffer *rb, TransactionId xid,
+									   Snapshot snapshot, XLogRecPtr lsn, RepOriginId origin_id,
+									   RelFileNode rnode, bool transactional, bool created,
+									   ReorderBufferTupleBuf *tuplebuf);
 void		ReorderBufferCommit(ReorderBuffer *, TransactionId,
 								XLogRecPtr commit_lsn, XLogRecPtr end_lsn,
 								TimestampTz commit_time, RepOriginId origin_id, XLogRecPtr origin_lsn);
@@ -682,4 +721,7 @@ void		ReorderBufferSetRestartPoint(ReorderBuffer *, XLogRecPtr ptr);
 
 void		StartupReorderBuffer(void);
 
+bool		ReorderBufferSequenceIsTransactional(ReorderBuffer *rb,
+												 RelFileNode rnode, bool created);
+
 #endif
-- 
2.31.1



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  To: [email protected]
  Cc: [email protected], [email protected], [email protected], [email protected], [email protected], [email protected]
  Subject: Re: logical decoding and replication of sequences
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