sqlite3 timestamp adapter chokes on timezones

[acdha]

BPO	19065
Nosy	@malemburg, @abalkin, @pitrou, @bitdancer, @berkerpeksag, @vajrasky, @iafisher
Files	add_timezone_support_for_sqlite3_datetime_adapter.patch: Initial patch by Chris Adams (acdha). Added support for negative timezone, doc, unit test and coding nitpick.

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2016-03-27.17:00:12.736>
created_at = <Date 2013-09-22.00:03:21.434>
labels = ['easy', 'type-feature', 'library']
title = 'sqlite3 timestamp adapter chokes on timezones'
updated_at = <Date 2021-10-07.11:07:17.431>
user = 'https://bugs.python.org/acdha'

bugs.python.org fields:

activity = <Date 2021-10-07.11:07:17.431>
actor = 'iafisher'
assignee = 'ghaering'
closed = True
closed_date = <Date 2016-03-27.17:00:12.736>
closer = 'berker.peksag'
components = ['Library (Lib)']
creation = <Date 2013-09-22.00:03:21.434>
creator = 'acdha'
dependencies = []
files = ['32253']
hgrepos = []
issue_num = 19065
keywords = ['patch', 'easy']
message_count = 10.0
messages = ['198234', '198269', '198288', '200590', '245836', '248826', '248834', '249009', '254314', '262526']
nosy_count = 10.0
nosy_names = ['lemburg', 'ghaering', 'belopolsky', 'pitrou', 'r.david.murray', 'berker.peksag', 'acdha', 'vajrasky', 'jacques-piguet', 'iafisher']
pr_nums = []
priority = 'normal'
resolution = 'rejected'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue19065'
versions = ['Python 3.4']

[acdha]

If you use detect_types=sqlite3.PARSE_DECLTYPES with sqlite3 and insert a timezone-aware datetime instance, you will get a ValueError if you attempt to read it back out:

File "/usr/local/Cellar/python3/3.3.2/Frameworks/Python.framework/Versions/3.3/lib/python3.3/sqlite3/dbapi2.py", line 68, in convert_timestamp
hours, minutes, seconds = map(int, timepart_full[0].split(b":"))
ValueError: invalid literal for int() with base 10: '03+00'

Although this immediately gets into the thorny stdlib timezone support situation, it's extremely annoying to have the out-of-the-box module break round-tripping data and it looks like support for simple UTC offsets isn't too horrible – something like https://gist.github.com/acdha/6655391 works in very limited testing:

def tz_aware_timestamp_adapter(val):
    datepart, timepart = val.split(b" ")
    year, month, day = map(int, datepart.split(b"-"))

    if b"+" in timepart:
        timepart, tz_offset = timepart.rsplit(b"+", 1)
        if tz_offset == b'00:00':
            tzinfo = datetime.timezone.utc
        else:
            hours, minutes = map(int, tz_offset.split(b':', 1))
            tzinfo = datetime.timezone(datetime.timedelta(hours=hours, minutes=minutes))
    else:
        tzinfo = None

    timepart_full = timepart.split(b".")
    hours, minutes, seconds = map(int, timepart_full[0].split(b":"))

    if len(timepart_full) == 2:
        microseconds = int('{:0<6.6}'.format(timepart_full[1].decode()))
    else:
        microseconds = 0

    val = datetime.datetime(year, month, day, hours, minutes, seconds, microseconds, tzinfo)

    return val

sqlite3.register_converter('timestamp', tz_aware_timestamp_adapter)

[pitrou]

This would be an useful improvement. Do you want to post a patch? See guidelines at http://docs.python.org/devguide/

[abalkin]

Sounds like a reasonable request, but the proposed code does not seem to work for the Eastern hemisphere (negative tz offsets.)

I am not very familiar with sqlite module. What timestamp format does it use? Isn't it some varian of ISO 3339? See bpo-15873.

[vajrasky]

Added patch to add timezone support for sqlite3 datetime adapter.

[jacques-piguet]

I just hit the problem in Python 2.7.
The patch given here is not applicable due to missing class "datetime.timezone" in Python before 3.2.

Question 1: when will the patch be applied in Python 3?
Question 2: any chance to get a solution in Python 2?

[ghaering]

I'm -1 on adding timezone to the adapters.

[bitdancer]

Can you expand on why you are -1, Gerhard?

[ghaering]

I'm -1 because I believe that ultimately, adapters and converters were a mistake to add to pysqlite. That's why I deprecated them in pysqlite 2.8.0.

Do you know what would be the correct step to propose a deprecation in the sqlite3 module of Python proper? Is a PEP necessary?

[bitdancer]

Just open an issue to propose the deprecation, if they aren't part of the DBAPI. We wouldn't actually remove them, though, until after 2.7 goes out of maintenance (if then...we still haven't quite decided what we're going to do about removals post 2.7).

[berkerpeksag]

Do you know what would be the correct step to propose a deprecation in the sqlite3 module of Python proper?

I've opened bpo-26651 (patch included) to deprecate them.