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Fix bug in temporal utilities due to DST being ignored. #955

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merged 3 commits into from
Nov 20, 2021

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novemberkilo
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Which issue does this PR close?

Closes #901

What changes are included in this PR?

Replaces the function using_chrono_tz with a function using_chrono_tz_and_utc_naive_datetime

The rationale for this is that an offset for a timezone depends on the point in time at which the offset is required -- it will vary depending on whether DST is in effect at that point in time or not.

Are there any user-facing changes?

I'm not sure. using_chrono_tz is a publicly available function (albeit under the chrono-tz feature flag) so strictly speaking the API is changing? If this is a concern, we could have both functions appear (with using_chrono_tz remaining unused).

What do you think @alamb ?

@github-actions github-actions bot added the arrow Changes to the arrow crate label Nov 18, 2021
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codecov-commenter commented Nov 18, 2021

Codecov Report

Merging #955 (7e0e187) into master (32d8c0a) will increase coverage by 0.01%.
The diff coverage is 100.00%.

Impacted file tree graph

@@            Coverage Diff             @@
##           master     #955      +/-   ##
==========================================
+ Coverage   82.31%   82.32%   +0.01%     
==========================================
  Files         168      168              
  Lines       48715    48713       -2     
==========================================
+ Hits        40100    40105       +5     
+ Misses       8615     8608       -7     
Impacted Files Coverage Δ
arrow/src/compute/kernels/temporal.rs 97.35% <100.00%> (+1.27%) ⬆️
parquet/src/encodings/encoding.rs 93.71% <0.00%> (+0.19%) ⬆️
arrow/src/array/transform/mod.rs 85.47% <0.00%> (+0.27%) ⬆️
parquet_derive/src/parquet_field.rs 66.43% <0.00%> (+0.45%) ⬆️

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None => $builder.append_null()?,
match $array.value_as_datetime(i) {
Some(utc) => {
let fixed_offset = match parse(
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As written, I think this code will try and parse $tz for each row in the array (even though the $tz is a constant).

I wonder if it would be possible to try and parse $tz once to figure out if it was fixed (e.g. a Some<FixedOffset>, and then only check if that was None for each row before computing using_chrono_tz_and_utc_naive_date_time

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Thanks for picking this up @alamb - I have addressed this in a subsequent commit.

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alamb commented Nov 18, 2021

Thank you @novemberkilo -- I appreciate the follow up

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Looks good @novemberkilo -- thank you

@alamb alamb merged commit 9703f98 into apache:master Nov 20, 2021
alamb pushed a commit that referenced this pull request Nov 22, 2021
* Check behaviour of temporal utilities for DST.

* Fix temporal util bug ignoring dst.

* Refactor macro for efficiency.
alamb pushed a commit that referenced this pull request Nov 23, 2021
* Check behaviour of temporal utilities for DST.

* Fix temporal util bug ignoring dst.

* Refactor macro for efficiency.
alamb added a commit that referenced this pull request Nov 23, 2021
* Check behaviour of temporal utilities for DST.

* Fix temporal util bug ignoring dst.

* Refactor macro for efficiency.

Co-authored-by: Navin <[email protected]>
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Temporal utilities miss variations due to daylight savings
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