pg_dump: Fix some schema issues when dumping sequences

In the new code for selecting sequence data from pg_sequence, set the
schema to pg_catalog instead of the sequences own schema, and refer to
the sequence by OID instead of name, which was missing a schema
qualification.
Reported-by: Stephen Frost <sfrost@snowman.net>

src/bin/pg_dump/pg_dump.c

@@ -15873,14 +15873,14 @@ dumpSequence(Archive *fout, TableInfo *tbinfo)
 	PQExpBuffer delqry = createPQExpBuffer();
 	PQExpBuffer labelq = createPQExpBuffer();
 
-	/* Make sure we are in proper schema */
-	selectSourceSchema(fout, tbinfo->dobj.namespace->dobj.name);
-
 	snprintf(bufm, sizeof(bufm), INT64_FORMAT, PG_INT64_MIN);
 	snprintf(bufx, sizeof(bufx), INT64_FORMAT, PG_INT64_MAX);
 
 	if (fout->remoteVersion >= 100000)
 	{
+		/* Make sure we are in proper schema */
+		selectSourceSchema(fout, "pg_catalog");
+
 		appendPQExpBuffer(query,
 						  "SELECT seqstart, seqincrement, "
 						  "CASE WHEN seqincrement > 0 AND seqmax = %s THEN NULL "
@@ -15894,12 +15894,20 @@ dumpSequence(Archive *fout, TableInfo *tbinfo)
 						  "seqcache, seqcycle "
 						  "FROM pg_class c "
 						  "JOIN pg_sequence s ON (s.seqrelid = c.oid) "
-						  "WHERE relname = ",
-						  bufx, bufm);
-		appendStringLiteralAH(query, tbinfo->dobj.name, fout);
+						  "WHERE c.oid = '%u'::oid",
+						  bufx, bufm,
+						  tbinfo->dobj.catId.oid);
 	}
 	else if (fout->remoteVersion >= 80400)
 	{
+		/*
+		 * Before PostgreSQL 10, sequence metadata is in the sequence itself,
+		 * so switch to the sequence's schema instead of pg_catalog.
+		 */
+
+		/* Make sure we are in proper schema */
+		selectSourceSchema(fout, tbinfo->dobj.namespace->dobj.name);
+
 		appendPQExpBuffer(query,
 						  "SELECT start_value, increment_by, "
 				   "CASE WHEN increment_by > 0 AND max_value = %s THEN NULL "
@@ -15916,6 +15924,9 @@ dumpSequence(Archive *fout, TableInfo *tbinfo)
 	}
 	else
 	{
+		/* Make sure we are in proper schema */
+		selectSourceSchema(fout, tbinfo->dobj.namespace->dobj.name);
+
 		appendPQExpBuffer(query,
 						  "SELECT 0 AS start_value, increment_by, "
 				   "CASE WHEN increment_by > 0 AND max_value = %s THEN NULL "