Timezone autodetection in thin mode is wrong

[szpajder]

1. What versions are you using?

Oracle 19c

platform.platform: Linux-6.4.10-arch1-1-x86_64-with-glibc2.38
sys.maxsize > 2**32: True
platform.python_version: 3.11.3

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

Error.

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

$ date
Wed Nov 22 16:27:47 CET 2023
$ python test.py
(datetime.datetime(2023, 11, 22, 17, 27, 52), '+02:00')

test.py is a script listed below. The current system timezone is CET (ie. winter time, which is +01:00) however oracledb autodetects it as +02:00 (summer time, CEST), regardless of the time of the year. As a result, all timestamps read from a database are OK during summer time, but off by 1 hour in winter time.

This is due to an incorrect autodetection logic in _get_alter_timezone_statement():

        if tz_repr is None:
            timezone = -time.altzone if time.daylight else -time.timezone

According to the docs, time.daylight indicates whether DST is defined for the current timezone, ie. if there is a time, past, present or future when daylight saving time applies. It does not indicate that DST is currently in use.

If I replace the above line with:

          timezone = time.localtime().tm_gmtoff

then it works fine, regardless of whether DST is currently in use or not.

4. Does your application call init_oracle_client()?

No.

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

import oracledb
with oracledb.connect(host='...', port=..., user='...',password='...',sid='...') as conn:
 with conn.cursor() as cursor:
  for row in cursor.execute('select current_date, sessiontimezone from dual'):
   print(row)

[anthony-tuininga]

Thank you for the clear explanation. I will make the suggested change!

[anthony-tuininga]

I have pushed a patch that should correct this bug. If you are able to build from source you can verify that it works for you.

[szpajder]

I've made exactly the same change and tested it before posting this issue - it works fine.

[anthony-tuininga]

The patch has been included in version 2.0.0 which was just released.