expression: handle mixed offsets and names zones in CONVERT_TZ

[dveeden]

• Support mixed named timezones and UTC offsets
• Add support for +14:00
• Support SYSTEM timezone

What problem does this PR solve?

This fixes the issues as reported in #8311

This fixes mixing named timezones like Europe/Moscow and UTC offsets like +01:00.

It also fixes support for the +14:00 timezone.

Check List

Tests

• Manual test (add detailed scripts or steps below)
• Unit tests

Documentation

• Affects user behaviors
• Changes MySQL compatibility

Release note

`CONVERT_TZ()` now supports mixing named timezones and UTC offsets

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• kennytm
• mjonss

To complete the pull request process, please ask the reviewers in the list to review by filling /cc @reviewer in the comment.
After your PR has acquired the required number of LGTMs, you can assign this pull request to the committer in the list by filling /assign @committer in the comment to help you merge this pull request.

The full list of commands accepted by this bot can be found here.

Reviewer can indicate their review by submitting an approval review.
Reviewer can cancel approval by submitting a request changes review.

[mjonss]

The CI found a broken test:

 builtin_time_test.go:2683:
     c.Assert(result, Equals, test.expect, Commentf("convert_tz(\"%v\", \"%s\", \"%s\")", test.t, test.fromTz, test.toTz))
 ... obtained string = "2004-01-01 12:00:00"
 ... expected string = ""
 ... convert_tz("2004-01-01 12:00:00", "+00:00", "GMT")

So this could probably be fixed and extended for testing this change too.

[dveeden]

/cc @mjonss

[mjonss]

LGTM, if you have time, then I would suggest adding named time zones to the tests as well, like 'Europe/Amsterdam', 'Asia/Shanghai'.

[mjonss]

Hmm, looks like it still has a bug, when adding one test with daylight saving time transition:

builtin_time_test.go:2690:
    c.Assert(result, Equals, test.expect, Commentf("convert_tz(\"%v\", \"%s\", \"%s\")", test.t, test.fromTz, test.toTz))
... obtained string = "2021-10-31 04:00:00"
... expected string = "2021-10-31 02:00:00"
... convert_tz("2021-10-31 02:00:00", "Europe/Amsterdam", "+02:00")

Fixed by adding:

t = t.In(time.UTC)

last in the else branch of fromTzMatched.

[bb7133]

LGTM, please address the comments from @mjonss

[bolt-juri-gavshin]

I would also recommend adding unit test equivalents of the following SQL clauses, if possible:

SELECT convert_tz('2021-10-31 02:59:59', 'Europe/Amsterdam', '+02:00'); -- return value is the same as input
SELECT convert_tz('2021-10-31 03:00:00', 'Europe/Amsterdam', '+01:00'); -- return value is the same as input

SELECT convert_tz('2021-10-31 02:59:59', '+02:00', 'Europe/Amsterdam'); -- return value is the same as input
SELECT convert_tz('2021-10-31 03:00:00', '+01:00', 'Europe/Amsterdam'); -- return value is the same as input

[kennytm]

LGTM, but I'd prefer the more uniform approach using time.FixedZone, so that a the conversion code itself always work on two *time.Locations, and doesn't need many if conditions.

[dveeden]

/assign @kennytm

[dveeden]

[2021-10-22T12:39:20.570Z] FAIL: builtin_time_test.go:2636: testEvaluatorSuite.TestConvertTz
[2021-10-22T12:39:20.570Z] 
[2021-10-22T12:39:20.570Z] builtin_time_test.go:2706:
[2021-10-22T12:39:20.570Z]     c.Assert(result, Equals, test.expect, Commentf("convert_tz(\"%v\", \"%s\", \"%s\")", test.t, test.fromTz, test.toTz))
[2021-10-22T12:39:20.570Z] ... obtained string = "2021-10-22 15:00:00"
[2021-10-22T12:39:20.570Z] ... expected string = "2021-10-22 03:00:00"
[2021-10-22T12:39:20.570Z] ... convert_tz("2021-10-22 10:00:00", "Europe/Tallinn", "SYSTEM")

 MySQL  127.0.0.1:4000 ssl  test  SQL > SELECT CONVERT_TZ("2021-10-22 10:00:00", "Europe/Tallinn", "Asia/Shanghai");
+----------------------------------------------------------------------+
| CONVERT_TZ("2021-10-22 10:00:00", "Europe/Tallinn", "Asia/Shanghai") |
+----------------------------------------------------------------------+
| 2021-10-22 15:00:00                                                  |
+----------------------------------------------------------------------+
1 row in set (0.0017 sec)

$ TZ=Asia/Shanghai date --date="TZ=\"Europe/Tallinn\" 2021-10-22 10:00:00" 
Fri 22 Oct 15:00:00 CST 2021

So looks like the expected string is wrong somehow.

[kennytm]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: a2107ee

[dveeden]

/label needs-cherry-pick-5.2

[ti-srebot]

cherry pick to release-5.2 in PR #29311

[ti-srebot]

cherry pick to release-5.3 in PR #32501