Max Gekk created SPARK-57809:
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Summary: Support nanosecond-precision timestamps in
collect_list/listagg ordering safety
Key: SPARK-57809
URL: https://issues.apache.org/jira/browse/SPARK-57809
Project: Spark
Issue Type: Sub-task
Components: SQL
Affects Versions: 4.3.0
Reporter: Max Gekk
This sub-task is part of the umbrella SPARK-56822 (timestamps with nanosecond
precision).
h2. Problem
{{collect.scala}} {{isCastEqualityPreserving}} (~L750-762) marks
{{TimestampNTZType}} as cast-equality-preserving and {{TimestampType}} (LTZ,
DST) as unsafe, but has no arm for {{TimestampNTZNanosType}} /
{{TimestampLTZNanosType}}, so both fall to {{case _ => false}}. NTZ nanos
should be treated like NTZ micro (safe); LTZ nanos like LTZ micro.
h2. Goal
Add nanosecond arms so the ORDER BY-cast optimization applies to NTZ nanos and
correctly excludes LTZ nanos, matching the microsecond behavior.
h2. Scope
Extend {{isCastEqualityPreserving}} (and any sibling checks) for
{{TimestampNTZNanosType}} and {{TimestampLTZNanosType}}.
h2. Acceptance criteria
* Ordered {{collect_list}} / {{listagg}} over NTZ nanos uses the safe path; LTZ
nanos keeps the same DST caveat as micro LTZ.
h2. Testing
{{collect.scala}}-related suites; targeted unit test.
h2. Dependencies
None - independent (builds on the resolved widening/cast infrastructure).
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