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

1 files changed, 105 insertions, 4 deletions

diff --git a/src/backend/replication/logical/tablesync.c b/src/backend/replication/logical/tablesync.c
index 1659964571c..d8b12d94bc3 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"
@@ -1000,6 +1001,95 @@ copy_table(Relation rel)
 }
 
 /*
+ * 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.
  *
  * The name must not exceed NAMEDATALEN - 1 because of remote node constraints
@@ -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)