Problem

DeleteBuilder::execute() (src/dataset/write/delete.rs:136) couples "compute deletion vector / rewrite fragments" with "advance HEAD via manifest commit" as a single operation. There is no public API to stage a delete (compute the DeleteData without advancing HEAD) and commit it later via CommitBuilder.

InsertBuilder::execute_uncommitted (src/dataset/write/insert.rs) and MergeInsertBuilder::execute_uncommitted both expose a public stage-then-commit shape that returns a Transaction for the caller to commit via CommitBuilder::execute.

The two-phase shape is already implemented internally for deletes. DeleteJob (private struct DeleteJob at src/dataset/write/delete.rs:152 — no visibility modifier; not exposed to consumers) implements RetryExecutor, splitting work into execute_impl() (build DeleteData) and commit(). DeleteJob::commit() at delete.rs:248-263 constructs Transaction::new(dataset.manifest.version, Operation::Delete { ... }, None) and then calls CommitBuilder::execute(transaction). The Transaction is built but never returned to callers.

What we'd like

A public DeleteBuilder::execute_uncommitted() -> Result<Transaction> method that runs the same execute_impl + Transaction construction that DeleteJob::commit runs today, but returns the Transaction instead of executing the commit:

let transaction = DeleteBuilder::new(dataset.clone(), "age > 65")
    .execute_uncommitted()
    .await?;
// ... do other work, decide whether to commit ...
let new_dataset = CommitBuilder::new(dataset).execute(transaction).await?;

Implementation-wise: split DeleteJob::commit() into "build Transaction" (already isolated at delete.rs:248-255) and "execute via CommitBuilder", then expose the build step through a new DeleteBuilder method. No new conflict-resolution work, no change to Operation::Delete's protobuf, no new internals.

References

• Lance distributed-write API (the model we want symmetry with): https://lance.org/guide/distributed_write/
• Lance Operation::Delete transaction type already exists in the format spec, so the on-disk shape is supported; just the writer-side API is internal.
• Sibling request: Multi-dataset atomic commit primitive #6668 (multi-dataset atomic commit). Together these would let a multi-statement, multi-table transaction stage every kind of write before flipping the manifest visible.
• Sibling request: Expose build_index_metadata_from_segments (or commit_existing_index_segments) for two-phase vector-index commits outside the lance crate #6666 (vector-index segment-commit API).