fat-catTW opened a new pull request, #72584:
URL: https://github.com/apache/airflow/pull/72584
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## Why
Mapped XCom sequence slices should match Python slicing semantics. When the
effective stop bound comes before the effective start bound, Python returns an
empty list.
The Execution API previously translated these crossed-bound slices into
SQLAlchemy `.slice(...)` calls that could generate a negative SQL `LIMIT`.
SQLite treated that as no limit and returned incorrect rows, while other
databases could reject the query.
relates: #69204
## Solution
Return an empty result before calling SQLAlchemy `.slice(...)` when the
translated slice bounds have crossed.
This keeps the endpoint consistent with Python slicing semantics and avoids
backend-specific behavior from negative SQL `LIMIT` values.
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