Enforce fractional-second precision end-to-end for TIME/DATETIME/TIME… #22728
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…STAMP, align with MySQL 8.0, add comprehensive tests (matrixorigin#22708) ### How it fixes: Add and use TruncateToScale for TIME; ensure Datetime/Timestamp/Time all apply scale consistently. Update CAST paths: Add timeToTime and datetimeToDatetime with TruncateToScale. Modify datetimeToTimestamp to accept targetScale and apply TruncateToScale. Ensure timestampToTimestamp/timestampToDatetime also apply target scale. Built-ins: apply TruncateToScale in current_timestamp/sysdate (and NOW family) per explicit scale; default behaves as scale 0. Type inference: restore scale=6 for string sources so literals keep full precision before truncation to target scale (MySQL 8.0 behavior). Tests: fix incorrect expectations in unit tests; rework flaky NOW tests; update plan_cache to use TIMESTAMP(6); add comprehensive BVT suites for TIME/DATETIME/TIMESTAMP covering rounding, boundaries, negatives, casts, arithmetic, comparisons, and functions; remove PASS/FAIL strings in results and assert via value outputs. ### Notes/impact: Breaking change: TIMESTAMP(0)/DATETIME(0)/TIME(0) now truly store/compare at seconds resolution. Workloads relying on microsecond differences at scale 0 must switch to scale 6. Aligns with MySQL 8.0 behavior; improves determinism; eliminates test flakiness. Approved by: @heni02, @ouyuanning
heni02
approved these changes
Oct 31, 2025
aunjgr
approved these changes
Oct 31, 2025
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What type of PR is this?
Which issue(s) this PR fixes:
issue #22701 #https://github.com/matrixorigin/MO-Cloud/issues/5761
What this PR does / why we need it:
How it fixes:
Add and use TruncateToScale for TIME; ensure Datetime/Timestamp/Time all apply scale consistently.
Update CAST paths:
Add timeToTime and datetimeToDatetime with TruncateToScale.
Modify datetimeToTimestamp to accept targetScale and apply TruncateToScale.
Ensure timestampToTimestamp/timestampToDatetime also apply target scale.
Built-ins: apply TruncateToScale in current_timestamp/sysdate (and NOW family) per explicit scale; default behaves as scale 0.
Type inference: restore scale=6 for string sources so literals keep full precision before truncation to target scale (MySQL 8.0 behavior).
Tests: fix incorrect expectations in unit tests; rework flaky NOW tests; update plan_cache to use TIMESTAMP(6); add comprehensive BVT suites for TIME/DATETIME/TIMESTAMP covering rounding, boundaries, negatives, casts, arithmetic, comparisons, and functions; remove PASS/FAIL strings in results and assert via value outputs.
Notes/impact:
Breaking change: TIMESTAMP(0)/DATETIME(0)/TIME(0) now truly store/compare at seconds resolution. Workloads relying on microsecond differences at scale 0 must switch to scale 6.
Aligns with MySQL 8.0 behavior; improves determinism; eliminates test flakiness.