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fix: Normalize Dask timestamps to UTC without a row-wise apply - #6818

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Daksha1611 wants to merge 2 commits into
feast-dev:masterfrom
Daksha1611:fix/dask-empty-entity-df
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Daksha1611 wants to merge 2 commits into
feast-dev:masterfrom
Daksha1611:fix/dask-empty-entity-df

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What this PR does / why we need it:

_normalize_timestamp made timestamp columns tz-aware with a row-wise apply that
declared meta=(timestamp_field, "datetime64[ns, UTC]"). meta only declares the
dtype — the partition gets whatever the lambda returns. With zero rows the lambda never
runs, so the computed column stayed tz-naive while meta claimed UTC, and the tz-aware
comparison in _filter_ttl then raised:

TypeError: Invalid comparison between dtype=datetime64[ns] and DatetimeArray

A zero-row entity_df is a normal case in batch scoring — the upstream query matched
nothing for that run — so get_historical_features crashed instead of returning an
empty result.

While fixing this I found the same mismatch on a second path: a column carrying a
non-UTC timezone also diverged from the declared meta, because the lambda returned any
value that already had tzinfo untouched. That is covered by a test here too.

Both applies are replaced with dd.to_datetime(..., utc=True), which localizes tz-naive
values, converts tz-aware ones, and yields the correct dtype for an empty frame. It is
also vectorized, so it drops a Python-level call per row on non-empty frames.

Which issue(s) this PR fixes:

Fixes #6817

Checks

  • I've made sure the tests are passing.
  • My commits are signed off (git commit -s)
  • My PR title follows conventional commits format

Testing Strategy

  • Unit tests
  • Integration tests
  • Manual tests
  • Testing is not required for this change

New sdk/python/tests/unit/infra/offline_stores/test_dask_empty_entity_df.py covers
normalization and TTL filtering at 0 and 1 rows, plus the non-UTC case. Three of its
five assertions fail on master and pass here; the two 1-row cases pass both ways,
pinning the non-empty behaviour as unchanged.

Verified end to end as well: get_historical_features(...).to_df() against a file
offline store with an otherwise identical entity frame raised TypeError at 0 rows
before this change, and now returns an empty frame with the expected columns while the
1-row case is unchanged.

sdk/python/tests/unit/infra/offline_stores plus test_unit_feature_store.py: 235
passed. The 20 errors in that run are MongoDB testcontainers failing to start locally
and are present on master too.

ruff check, ruff format --check and mypy are clean on both changed files.

Misc

Point-in-time correctness is unaffected — I re-ran the filter_by_created_timestamp
scenario (a row backfilled after the entity timestamp) and it still excludes the late
row with the flag and includes it without.

_normalize_timestamp made timestamp columns tz-aware with a row-wise apply
declaring meta="datetime64[ns, UTC]". meta only declares the dtype; the
partition gets whatever the lambda returns. With zero rows the lambda never
runs, so the computed column stayed tz-naive while meta claimed UTC, and the
tz-aware comparison in _filter_ttl then raised:

    TypeError: Invalid comparison between dtype=datetime64[ns] and DatetimeArray

A zero-row entity_df is a normal case in batch scoring, when the upstream
query matched nothing for that run, so get_historical_features crashed rather
than returning an empty result.

A column carrying a non-UTC timezone diverged from the declared meta the same
way, because the lambda returned any value that already had tzinfo untouched.

Replace both applies with dd.to_datetime(..., utc=True), which localizes
tz-naive values, converts tz-aware ones, and yields the correct dtype for an
empty frame. It is also vectorized, so it avoids a Python-level call per row
on non-empty frames.

Signed-off-by: Daksha1611 <mehtadaksha1611@gmail.com>
@Daksha1611
Daksha1611 requested a review from a team as a code owner September 6, 2026 18:33
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Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 47.08%. Comparing base (5ad5592) to head (042397e).
⚠️ Report is 1 commits behind head on master.
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Additional details and impacted files

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@@            Coverage Diff             @@
##           master    #6818      +/-   ##
==========================================
- Coverage   47.08%   47.08%   -0.01%     
==========================================
  Files         419      419              
  Lines       51878    51876       -2     
  Branches     7525     7525              
==========================================
- Hits        24429    24427       -2     
  Misses      25700    25700              
  Partials     1749     1749              
Flag Coverage Δ *Carryforward flag
go-feature-server 30.58% <ø> (ø)
python-unit 48.39% <ø> (-0.01%) ⬇️ Carriedforward from 5ad5592

*This pull request uses carry forward flags. Click here to find out more.

Files with missing lines Coverage Δ
sdk/python/feast/infra/offline_stores/dask.py 52.19% <ø> (-0.19%) ⬇️

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get_historical_features raises TypeError on a zero-row entity_df (Dask/file offline store)

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