Add support for named time zones in thin mode

issue にある実行可能な Python スクリプトから始め、指定された Oracle 11g とドライバーのセットアップで、失敗する名前付きタイムゾーンのクエリと成功する timestamp クエリを比較します。完了条件は、名前付きタイムゾーンを使用して timestamp を取得すると、タイムゾーン情報を保持した datetime 値が返されることです。TIMESTAMP WITH TIME ZONE のテーブル例も対象にします。

Fetching timestamp with time zone raises error ORA-01805: possible error in date/time operation instead of returning datetime with time zone information.

1. What versions are you using?

   • database version: Oracle Database 11g Express Edition Release 11.2.0.2.0 - 64bit Production
   • platform.python_version: 3.9.9
   • oracledb.__version__: 1.0.1

2. Is it an error or a hang or a crash? Error

3. What error(s) or behavior you are seeing?

Error oracledb.exceptions.DatabaseError: ORA-01805: possible error in date/time operation is raised when trying to use at time zone in SQL . Below is a sample code to reproduce the problem.

5. Does your application call init_oracle_client()? Yes, uses Thick mode.

6. Include a runnable Python script that shows the problem.

import oracledb
from oracledb.thick_impl import init_oracle_client


def f(sql):
    with oracledb.connect(user='hr', password='password', dsn='127.0.0.1:1511/xe') as connection:
        with connection.cursor() as cursor:
            query = cursor.execute(sql)
            row = query.fetchone()
            print(row[0].time())


init_oracle_client()

# this works because returns datetime without time zone
f("select systimestamp from dual")

# this raises error ORA-01805
f("select systimestamp at time zone 'America/Montreal' as d from dual")


# this is manual walkaround but datetime is still missing time zone information
f("select cast(systimestamp at time zone 'America/Montreal' as timestamp) as d from dual")

The above is an example using systimestamp but similar error can be achieved by crating table with column type timestamp with time zone

create table tz_table
(
	tz_timestamp TIMESTAMP(6) WITH TIME ZONE not null
);

insert into tz_table values ( TIMESTAMP '2022-06-16 08:00:00 US/Central');