Fix: Unexpected backfill of a parent when an interval outside the parent's range is restated for a child

[izeigerman]

The issue might occur when the parent's start is inferred to be later (greater) than the child's and the restated interval is outside the parent's range. In this case a parent is backfilled unexpectedly.

[Copilot]

Pull Request Overview

This PR fixes an issue where a parent model was unexpectedly backfilled when restating a child model's interval that falls outside the parent's range. The fix ensures that when a parent's start date is inferred to be later than a child's, restating intervals outside the parent's range won't trigger unnecessary parent backfills.

Key changes:

• Modified missing_intervals() to check if the computed start date exceeds the end date before processing intervals
• Refactored start_date() to only consider parent start dates when they exist, falling back to cron-based computation otherwise
• Added comprehensive test coverage for the restatement edge case

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
sqlmesh/core/snapshot/definition.py	Fixed logic in missing_intervals() to validate date ranges earlier and refactored start_date() to properly handle parent start date inference
tests/core/integration/test_restatement.py	Added test case validating that restating a child model outside parent's date range doesn't trigger unexpected parent backfills

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[themisvaltinos]

in the case where a snapshot has parents it never considers its own start, shouldn't it still consider it here similar to before so have something like:

  cron_start = snapshot.node.cron_prev(snapshot.node.cron_floor(relative_to or now()))
  earliest = min([cron_start] + parent_starts) if parent_starts else cron_start

[themisvaltinos]

actually I see now this is needed to constrain the data of the child to avoid the backfill of parents