fix(db_engine_specs): use fixed Monday week start for Oracle and Impala Week grain by dhruv-techdev · Pull Request #45858 · apache/superset

dhruv-techdev · 2026-10-29T19:15:54Z

SUMMARY

The Week time grain for Oracle and Impala used TRUNC(..., 'WW'). In both databases, 'WW' truncates to the same weekday as January 1st, not to a fixed week start. As a result:

The weekday a week starts on changes every year (2025 weeks start on Wednesday, 2026 weeks on Thursday).
Every year ends with a 1-day "week" (2 days in leap years), e.g. 2025-12-31 gets its own bucket.
Weeks never cross a year boundary.

This PR changes the unit to one that always truncates to Monday, matching the fixed week start used by other engines:

Oracle: 'WW' → 'IW' (ISO week). 'IW' doesn't depend on NLS_TERRITORY, unlike 'D'/'DY'.
Impala: 'WW' → 'D'. Impala's TRUNC does not accept 'IW'; 'D'/'DY'/'DAY' truncate to the previous Monday (see TruncDayOfWeek / StrToTruncUnit in be/src/exprs/udf-builtins.cc).

The change is one line per engine spec, plus a regression test for each that pins the generated SQL.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Oracle Database 23ai Free (gvenzl/oracle-free:23-slim). BEFORE (WW) is the old TimeGrain.WEEK expression and AFTER (IW) is the new one:

TESTING INSTRUCTIONS

Unit tests

pytest tests/unit_tests/db_engine_specs/test_oracle.py tests/unit_tests/db_engine_specs/test_impala.py

Both new tests fail on master ('WW' vs 'IW' / 'D') and pass with this change.

Manual check on Oracle

docker run -d --name oracle-ww -p 1521:1521 -e ORACLE_PASSWORD=test gvenzl/oracle-free:23-slim
until docker logs oracle-ww 2>&1 | grep -q "DATABASE IS READY TO USE"; do sleep 5; done
docker exec -i oracle-ww sqlplus -s system/test@//localhost/FREEPDB1 <<'SQL'
ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD DY';
SELECT d, TRUNC(CAST(d AS DATE), 'WW') AS old_week, TRUNC(CAST(d AS DATE), 'IW') AS new_week
FROM (
  SELECT DATE '2025-12-30' d FROM dual UNION ALL
  SELECT DATE '2025-12-31'   FROM dual UNION ALL
  SELECT DATE '2026-01-05'   FROM dual
);
SQL
docker rm -f oracle-ww

new_week should always be a Monday. In the UI, a time-series chart on an Oracle dataset with Time grain = Week should show Monday-aligned buckets and no stub week at year end.

ADDITIONAL INFORMATION

Has associated issue: Fixes Oracle and Impala "Week" time grain uses TRUNC(..., 'WW'): week start shifts every year and each year ends with a 1–2 day stub week #45857
Required feature flags:
Changes UI
Includes DB Migration (follow approval process in SIP-59)
- Migration is atomic, supports rollback & is backwards-compatible
- Confirm DB migration upgrade and downgrade tested
- Runtime estimates and downtime expectations provided
Introduces new feature or API
Removes existing feature or API

Notes for reviewers

Oracle behaviour was verified on a live Oracle 23ai Free instance (output above). Impala's 'D' is verified against the Impala source; it has not been run on a live Impala instance.
Existing Oracle/Impala charts using the Week grain will regroup into Monday-start weeks. Happy to add an UPDATING.md entry if reviewers consider this a breaking change.

…la Week grain

codecov · 2026-10-29T19:34:21Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.73%. Comparing base (8262ab9) to head (6a46056).
⚠️ Report is 4 commits behind head on master.

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rebenitez1802

LGTM, thanks for the fix! I checked the Impala side against a live Impala 4.5.2: TRUNC(x, 'D') returns the same-or-previous Monday for every date I tried (a 4,000-day sweep). It also works on TIMESTAMP, DATE, STRING and NULL inputs, and 'D' is as old in Impala as 'WW', so older versions are covered too. On Oracle, 'IW' is the ISO Monday and doesn't depend on NLS_TERRITORY. The only subclass is AscendEngineSpec, and it overrides the grains, so it isn't affected. Bonus: time comparison already keys weeks Monday-first (%Y-W%W), so this also fixes misaligned week-over-week joins.

One non-blocking note inline about UPDATING.md. Also, the PR title got truncated ("…Impa…"); it would be worth restoring the full title before merge.

rebenitez1802 · 2026-10-30T19:44:21Z

        TimeGrain.HOUR: "TRUNC(CAST({col} as DATE), 'HH')",
        TimeGrain.DAY: "TRUNC(CAST({col} as DATE), 'DDD')",
-        TimeGrain.WEEK: "TRUNC(CAST({col} as DATE), 'WW')",
+        TimeGrain.WEEK: "TRUNC(CAST({col} as DATE), 'IW')",


🟡 Medium: add an UPDATING.md note for the Week regrouping (non-blocking)

This changes how existing Oracle and Impala Week-grain charts are bucketed. Week starts can move by up to 6 days, the 1–2 day stub at year end disappears, and per-bucket totals change. The query cache key doesn't include the generated SQL, so results cached under 'WW' keep being served until their TTL expires. The Db2 week-grain change (#43236) documented the same kind of shift in UPDATING.md.

UPDATING.md isn't part of this diff, so GitHub can't offer an applyable suggestion there. Here is an entry for the ## Next section:

- The `Week` time grain for Oracle (`TRUNC(..., 'IW')`) and Impala (`TRUNC(..., 'D')`) now always truncates to Monday. Previously `'WW'` aligned weeks to the weekday of January 1, so the week start changed every year and each year ended with a 1–2 day stub week. Existing Week-grain charts on these engines will regroup, and cached results may show the old buckets until they expire.

Thanks for the thorough review, and for verifying 'D' on a live Impala!

Added your entry to the ## Next section of UPDATING.md in cd1ed69, and merged the latest master to resolve the conflict with the other new entries there. I also restored the full PR title.

netlify · 2026-10-30T22:02:09Z

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…-week-grain # Conflicts: # UPDATING.md

codeant-ai-for-open-source · 2026-10-30T22:08:40Z

CodeAnt PR Risk

🟢 Low Risk

The PR appears safe to merge; no actionable issues were identified in the review.

Assessed commit: 6a46056ccebd

fix(db_engine_specs): use fixed Monday week start for Oracle and Impa…

1a3a759

…la Week grain

pull-request-size Bot added the size/S label Oct 29, 2026

sadpandajoe requested review from gabotorresruiz and rebenitez1802 October 30, 2026 17:13

rebenitez1802 approved these changes Oct 30, 2026

View reviewed changes

dhruv-techdev changed the title ~~fix(db_engine_specs): use fixed Monday week start for Oracle and Impa…~~ fix(db_engine_specs): use fixed Monday week start for Oracle and Impala Week grain Oct 30, 2026

docs(updating): note Oracle and Impala Week grain regrouping

cd1ed69

pull-request-size Bot added size/M and removed size/S labels Oct 30, 2026

Merge remote-tracking branch 'upstream/master' into fix/oracle-impala…

6a46056

…-week-grain # Conflicts: # UPDATING.md

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fix(db_engine_specs): use fixed Monday week start for Oracle and Impala Week grain - #45858

fix(db_engine_specs): use fixed Monday week start for Oracle and Impala Week grain#45858
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dhruv-techdev commented Oct 29, 2026

SUMMARY

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

TESTING INSTRUCTIONS

ADDITIONAL INFORMATION

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