static void quoteExternalName(StringBuilder sb, String externalName) {
        List<String> parts = splitByNonQuotedDots(externalName);
        for (int i = 0; i < parts.size(); i++) {
            String unescaped = unescapeQuotes(parts.get(i));
            String unquoted = unquoteIfQuoted(unescaped);
            DIALECT.quoteIdentifier(sb, unquoted);
            if (i < parts.size() - 1) {
                sb.append(".");
            }
        }
    }
@Test
    public void quoteExternalName_with_2dots() {
        String externalName = "catalog.custom_schema.my_table";
        StringBuilder sb = new StringBuilder();
        MappingHelper.quoteExternalName(sb, externalName);
        assertThat(sb.toString()).isEqualTo("\"catalog\".\"custom_schema\".\"my_table\"");
    }