Fix adding sub-second intervals to DateTime

[al13n321]

Changelog category (leave one):

• Bug Fix (user-visible misbehavior in an official stable release)

Changelog entry (a user-readable short description of the changes that goes to CHANGELOG.md):

Fixed adding intervals of a fraction of a second to DateTime producing incorrect result.

Closes #45779

:) select toDateTime('2000-01-01') + interval 1 millisecond

Before:

┌─plus(toDateTime('2000-01-01'), toIntervalMillisecond(0))─┐
│                                      2026-10-14 16:21:20 │
└──────────────────────────────────────────────────────────┘

After:

┌─plus(toDateTime('2000-01-01'), toIntervalMillisecond(1))─┐
│                                  2000-01-01 00:00:00.001 │
└──────────────────────────────────────────────────────────┘

It was a simple bug in AddNanosecondsImpl/etc - it was returning a wrong type.

---

Along the way added a check for this overflow (very incomplete, other overflows remain unchecked):

:) select toDateTime64('3000-01-01 12:00:00.12345', 0) + interval 0 nanosecond

Before:

┌─plus(toDateTime64('3000-01-01 12:00:00.12345', 0), toIntervalNanosecond(0))─┐
│                                               1900-01-01 00:00:00.290448384 │
└─────────────────────────────────────────────────────────────────────────────┘

After:

Received exception:
Code: 407. DB::Exception: Decimal math overflow: While processing toDateTime64('3000-01-01 12:00:00.12345', 0) + toIntervalNanosecond(0). (DECIMAL_OVERFLOW)

---

And made incompatible types get rejected during typechecking rather than execution:

:) select toTypeName(materialize(toDate('2000-01-01')) + interval 1 nanosecond)

Before:

┌─toTypeName(plus(materialize(toDate('2000-01-01')), toIntervalNanosecond(1)))─┐
│ DateTime64(9)                                                                │
└──────────────────────────────────────────────────────────────────────────────┘

After:

Received exception:
Code: 43. DB::Exception: addNanoseconds cannot be used with Date: While processing toTypeName(materialize(toDate('2000-01-01')) + toIntervalNanosecond(1)). (ILLEGAL_TYPE_OF_ARGUMENT)

[robot-ch-test-poll4]

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[antonio2368]

maybe throw a logical error in cases like this?
Returning 0 seems strange on something that shouldn't be called + it could make it harder to debug.

[al13n321]

Yeah, that sounds better, changing.

[al13n321]

Stress test (debug): #53454

[tavplubix]

The new test is flaky:
https://s3.amazonaws.com/clickhouse-test-reports/0/407bb57ba9b4727b135635d3e6479f9e635b6ded/stateless_tests__release__s3_storage__[1_2].html

https://s3.amazonaws.com/clickhouse-test-reports/53673/61f4b6e2294a13541e8304336b427bcbafb199a9/stateless_tests__debug__s3_storage__[1_6].html

[al13n321]

The new test is flaky:

Wow, a simple toDateTime('2000-01-01 12:00:00') + INTERVAL 1234567 SECOND produced a result that's off by exactly one hour. Must be something related to timezones. But what exactly? The only thing I can think of is session's or server's timezone changing between the toDateTime execution and the formatting of the results; but AFAICT server timezone can't change at runtime and session timezone can't change without the test doing any queries to change it. What else can it be? Am I misunderstanding how timezones work in CH?

[tavplubix]

Maybe this is the culprit:

ClickHouse/tests/clickhouse-test

Lines 613 to 624 in 16cbda1

	"session_timezone": lambda: random.choice(
	[
	# special non-deterministic around 1970 timezone, see [1].
	#
	# [1]: https://github.com/ClickHouse/ClickHouse/issues/42653
	"America/Mazatlan",
	"America/Hermosillo",
	"Mexico/BajaSur",
	# server default that is randomized across all timezones
	# NOTE: due to lots of trickery we cannot use empty timezone here, but this should be the same.
	get_localzone(),
	]

[al13n321]

Ah, turns out the real timezone randomization is in docker/test/stateless/run.sh rather than tests/clickhouse-test, that's why I couldn't reproduce it locally. Fix in #53906