Add decoding of sequences to built-in replication

This commit adds support for decoding of sequences to the built-in
replication (the infrastructure was added by commit 0da92dc530).

The syntax and behavior mostly mimics handling of tables, i.e. a
publication may be defined as FOR ALL SEQUENCES (replicating all
sequences in a database), FOR ALL SEQUENCES IN SCHEMA (replicating
all sequences in a particular schema) or individual sequences.

To publish sequence modifications, the publication has to include
'sequence' action. The protocol is extended with a new message,
describing sequence increments.

A new system view pg_publication_sequences lists all the sequences
added to a publication, both directly and indirectly. Various psql
commands (\d and \dRp) are improved to also display publications
including a given sequence, or sequences included in a publication.

Author: Tomas Vondra, Cary Huang
Reviewed-by: Peter Eisentraut, Amit Kapila, Hannu Krosing, Andres
             Freund, Petr Jelinek
Discussion: https://postgr.es/m/d045f3c2-6cfb-06d3-5540-e63c320df8bc@enterprisedb.com
Discussion: https://postgr.es/m/1710ed7e13b.cd7177461430746.3372264562543607781@highgo.ca

src/backend/replication/logical/proto.c

@@ -648,6 +648,56 @@ 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,
+						  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_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->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 +1253,8 @@ 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);

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"
@@ -999,6 +1000,95 @@ copy_table(Relation rel)
 	logicalrep_rel_close(relmapentry, NoLock);
 }
 
+/*
+ * Fetch sequence data (current state) from the remote node.
+ */
+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;
+	List	   *qual = NIL;
+	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, &qual);
+
+	/* sequences don't have row filters */
+	Assert(!qual);
+
+	/* 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);
+
+	/* tablesync sets the sequences in non-transactional way */
+	SetSequence(RelationGetRelid(rel), false, last_value, log_cnt, is_called);
+
+	logicalrep_rel_close(relmapentry, NoLock);
+}
+
 /*
  * Determine the tablesync slot name.
  *
@@ -1260,10 +1350,21 @@ LogicalRepSyncTableStart(XLogRecPtr *origin_startpos)
 						originname)));
 	}
 
-	/* Now do the initial data copy */
-	PushActiveSnapshot(GetTransactionSnapshot());
-	copy_table(rel);
-	PopActiveSnapshot();
+	/* Do the right action depending on the relation kind. */
+	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)

src/backend/replication/logical/worker.c

@@ -143,6 +143,7 @@
 #include "catalog/pg_subscription.h"
 #include "catalog/pg_subscription_rel.h"
 #include "catalog/pg_tablespace.h"
+#include "commands/sequence.h"
 #include "commands/tablecmds.h"
 #include "commands/tablespace.h"
 #include "commands/trigger.h"
@@ -1143,6 +1144,57 @@ 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 SetSequence). 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 SetSequence */
+	LockRelationOid(relid, AccessExclusiveLock);
+
+	/* apply the sequence change */
+	SetSequence(relid, seq.transactional, 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.
  */
@@ -2511,6 +2563,10 @@ 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;

src/backend/replication/pgoutput/pgoutput.c

@@ -15,6 +15,7 @@
 #include "access/tupconvert.h"
 #include "catalog/partition.h"
 #include "catalog/pg_publication.h"
+#include "catalog/pg_publication_namespace.h"
 #include "catalog/pg_publication_rel.h"
 #include "commands/defrem.h"
 #include "executor/executor.h"
@@ -53,6 +54,10 @@ 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 relation, bool transactional,
+							  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,
@@ -208,6 +213,7 @@ _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;
@@ -224,6 +230,7 @@ _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;
@@ -237,6 +244,7 @@ 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;
 
@@ -244,6 +252,7 @@ parse_output_parameters(List *options, PGOutputData *data)
 	data->streaming = false;
 	data->messages = false;
 	data->two_phase = false;
+	data->sequences = true;
 
 	foreach(lc, options)
 	{
@@ -312,6 +321,16 @@ 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)
@@ -1440,6 +1459,51 @@ pgoutput_message(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 	OutputPluginWrite(ctx, true);
 }
 
+static void
+pgoutput_sequence(LogicalDecodingContext *ctx,
+				  ReorderBufferTXN *txn, XLogRecPtr sequence_lsn,
+				  Relation relation, bool transactional,
+				  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(relation))
+		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, relation);
+
+	/*
+	 * 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,
+							  relation,
+							  xid,
+							  sequence_lsn,
+							  transactional,
+							  last_value,
+							  log_cnt,
+							  is_called);
+	OutputPluginWrite(ctx, true);
+}
+
 /*
  * Currently we always forward.
  */
@@ -1725,7 +1789,8 @@ get_rel_sync_entry(PGOutputData *data, Relation relation)
 		entry->schema_sent = false;
 		entry->streamed_txns = NIL;
 		entry->pubactions.pubinsert = entry->pubactions.pubupdate =
-			entry->pubactions.pubdelete = entry->pubactions.pubtruncate = false;
+			entry->pubactions.pubdelete = entry->pubactions.pubtruncate =
+			entry->pubactions.pubsequence = false;
 		entry->new_slot = NULL;
 		entry->old_slot = NULL;
 		memset(entry->exprstate, 0, sizeof(entry->exprstate));
@@ -1739,13 +1804,13 @@ get_rel_sync_entry(PGOutputData *data, Relation relation)
 	{
 		Oid			schemaId = get_rel_namespace(relid);
 		List	   *pubids = GetRelationPublications(relid);
-
+		char		objectType = pub_get_object_type_for_relkind(get_rel_relkind(relid));
 		/*
 		 * We don't acquire a lock on the namespace system table as we build
 		 * the cache entry using a historic snapshot and all the later changes
 		 * are absorbed while decoding WAL.
 		 */
-		List	   *schemaPubids = GetSchemaPublications(schemaId);
+		List	   *schemaPubids = GetSchemaPublications(schemaId, objectType);
 		ListCell   *lc;
 		Oid			publish_as_relid = relid;
 		int			publish_ancestor_level = 0;
@@ -1780,6 +1845,7 @@ get_rel_sync_entry(PGOutputData *data, Relation relation)
 		entry->pubactions.pubupdate = false;
 		entry->pubactions.pubdelete = false;
 		entry->pubactions.pubtruncate = false;
+		entry->pubactions.pubsequence = false;
 
 		/*
 		 * Tuple slots cleanups. (Will be rebuilt later if needed).
@@ -1826,9 +1892,11 @@ get_rel_sync_entry(PGOutputData *data, Relation relation)
 
 			/*
 			 * If this is a FOR ALL TABLES publication, pick the partition root
-			 * and set the ancestor level accordingly.
+			 * and set the ancestor level accordingly. If this is a FOR ALL
+			 * SEQUENCES publication, we publish it too but we don't need to
+			 * pick the partition root etc.
 			 */
-			if (pub->alltables)
+			if (pub->alltables || pub->allsequences)
 			{
 				publish = true;
 				if (pub->pubviaroot && am_partition)
@@ -1889,6 +1957,7 @@ get_rel_sync_entry(PGOutputData *data, Relation relation)
 				entry->pubactions.pubupdate |= pub->pubactions.pubupdate;
 				entry->pubactions.pubdelete |= pub->pubactions.pubdelete;
 				entry->pubactions.pubtruncate |= pub->pubactions.pubtruncate;
+				entry->pubactions.pubsequence |= pub->pubactions.pubsequence;
 
 				/*
 				 * We want to publish the changes as the top-most ancestor