Validate replaced data files during commit retries

[kevinjqliu]

Summary

• validate that explicitly replaced data files still exist when an overwrite retries
• add regression coverage for conflicting and unrelated concurrent file deletions

Follow-up to #3780.

Why this validation is needed

Suppose transaction A is replacing data file F with a newly written file F2. Before A commits, transaction B deletes F and commits. A then refreshes the table and retries its commit.

The retry must fail. If A commits F2, it puts data derived from F back into the table and can undo B's deletion.

The existing checks do not catch this case:

• delete_data_file(F) records a specific file, not a row predicate, so predicate-based deleted-file validation has nothing to match.
• _validate_no_new_deletes_for_data_files checks newly added position or equality delete files. Transaction B removed a data file instead.

_validate_data_files_exist provides the missing check: before retrying, verify that every file being replaced is still present. The scan is narrowed by spec and partition, but only an exact file match causes a conflict.

Scenarios tested

Concurrent deletion	Expected result
Exact file being replaced	Fail
Different file in the same partition	Succeed
File in a different partition	Succeed

All three cases are covered by test_file_overwrite_validates_concurrent_file_delete and run against all three catalog fixtures.

Java alignment

Iceberg Java handles the same concerns separately:

• failMissingDeletePaths requires an overwrite's target files to still exist.
• validateDataFilesExist checks exact required file paths against concurrent data-file removals.
• validateNoNewDeletesForDataFiles separately checks newly added row-level delete files.

Java also tests unrelated concurrent deletion succeeding and target-file deletion failing.

Tests

• 9 regression-test executions: 3 scenarios × 3 catalog fixtures
• all commit hooks passed

[Copilot]

Pull request overview

Adds commit-retry validation to prevent an overwrite that explicitly replaces a data file from succeeding if the replaced (target) file was concurrently deleted by another transaction, avoiding resurrecting data from a removed file.

Changes:

• Add _validate_data_files_exist to detect concurrent deletions of explicitly targeted/replaced data files during the retry validation window.
• Wire the new validation into snapshot concurrency validation when a commit has specific deleted/replaced data files tracked.
• Add a regression test covering conflicting and non-conflicting concurrent deletions (same file, different file same partition, different partition) across all catalog fixtures.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
pyiceberg/table/update/validate.py	Adds validation to detect concurrent deletion of specific required/replaced data files.
pyiceberg/table/update/snapshot.py	Invokes the new validation during concurrency checks when explicit deleted/replaced files are present.
tests/table/test_commit_retry.py	Adds regression coverage for overwrite retries with concurrent data-file deletions.

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