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Which issue does this PR close?

Closes #3180

Rationale for this change

Spark TimestampNTZ values represent local time without any timezone
information. However, the current Comet implementation applies timezone
conversion when evaluating hour, minute, and second, which leads to
incorrect results for TimestampNTZ inputs in non-UTC session timezones.

This change aligns Comet behavior with Spark semantics by ensuring that
timezone conversion is only applied to Timestamp values with an explicit
timezone, and not to TimestampNTZ.

What changes are included in this PR?

  • Updated the Rust implementation of extract_date_part used by
    hour, minute, and second to:
    • Bypass timezone conversion for TimestampNTZ inputs
    • Preserve existing behavior for Timestamp inputs with timezone
  • Added defensive handling for unsupported input types

How are these changes tested?

  • Verified via Rust unit tests:
    cargo test -p datafusion-comet-spark-expr

Copilot AI review requested due to automatic review settings January 24, 2026 16:19
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Pull request overview

Aligns Comet’s hour/minute/second behavior with Spark semantics by avoiding session-timezone conversion for TimestampNTZ (timestamp without timezone), while preserving the existing conversion behavior for timezone-aware timestamps.

Changes:

  • Bypass timezone conversion for DataType::Timestamp(_, None) (TimestampNTZ) inputs.
  • Preserve timezone conversion for DataType::Timestamp(_, Some(_)) inputs via array_with_timezone.
  • Add an explicit execution error for unsupported (non-timestamp) input types.

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Comment on lines +79 to +85
let array = match array.data_type() {
// TimestampNTZ → DO NOT apply timezone conversion
DataType::Timestamp(_, None) => array.clone(),

// Timestamp with timezone → convert from UTC to session timezone
DataType::Timestamp(_, Some(_)) => array_with_timezone(
array,
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Copilot AI Jan 24, 2026

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invoke_with_args now pattern-matches directly on array.data_type() and rejects DataType::Dictionary(_, _) with an execution error. This is a regression for dictionary-encoded timestamp columns (the function’s return_type explicitly supports dictionary input, and array_with_timezone also has dictionary handling). Add explicit handling for DataType::Dictionary(_, value_type) where value_type is Timestamp(_, None) (no conversion) or Timestamp(_, Some(_)) (apply array_with_timezone), instead of falling into the error branch.

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Successfully merging this pull request may close these issues.

[Bug] hour/minute/second expressions incorrectly apply timezone conversion to TimestampNTZ inputs

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