/// <summary>
        /// Parses COMMENT ON INDEX.
        /// </summary>
        private static void ParseIndex(Parser parser, PgDatabase database)
        {
            var indexName = parser.ParseIdentifier();

            var objectName = ParserUtils.GetObjectName(indexName);

            var schemaName = ParserUtils.GetSchemaName(indexName, database);

            if (database.SchemaIsIgnored(schemaName))
            {
                return;
            }

            PgSchema schema = database.GetSchema(schemaName);

            PgIndex index = schema.GetIndex(objectName);

            if (index == null)
            {
                PgConstraint primaryKey = schema.GetPrimaryKey(objectName);
                parser.Expect("IS");
                primaryKey.Comment = GetComment(parser);
                parser.Expect(";");
            }
            else
            {
                parser.Expect("IS");
                index.Comment = GetComment(parser);
                parser.Expect(";");
            }
        }