feat: implement bindings to return merge stats

[xaptronic]

Based on this comment: https://github.com/lancedb/lancedb/issues/2228#issuecomment-2730463075 and https://github.com/lancedb/lance/pull/2357

Here is my attempt at implementing bindings for returning merge stats from a merge_insert.execute call for lancedb.

Note: I have almost no idea what I am doing in Rust but tried to follow existing code patterns and pay attention to compiler hints.

• The change in nodejs binding appeared to be necessary to get compilation to work, presumably this could actual work properly by returning some kind of NAPI JS object of the stats data?
• I am unsure of what to do with the remote/table.rs changes - necessarily for compilation to work; I assume this is related to LanceDB cloud, but unsure the best way to handle that at this point.

Proof of function:

import pandas as pd
import lancedb


db = lancedb.connect("/tmp/test.db")

test_data = pd.DataFrame(
    {
        "title": ["Hello", "Test Document", "Example", "Data Sample", "Last One"],
        "id": [1, 2, 3, 4, 5],
        "content": [
            "World",
            "This is a test",
            "Another example",
            "More test data",
            "Final entry",
        ],
    }
)

table = db.create_table("documents", data=test_data, exist_ok=True, mode="overwrite")

update_data = pd.DataFrame(
    {
        "title": [
            "Hello, World",
            "Test Document, it's good",
            "Example",
            "Data Sample",
            "Last One",
            "New One",
        ],
        "id": [1, 2, 3, 4, 5, 6],
        "content": [
            "World",
            "This is a test",
            "Another example",
            "More test data",
            "Final entry",
            "New content",
        ],
    }
)

stats = (
    table.merge_insert(on="id")
    .when_matched_update_all()
    .when_not_matched_insert_all()
    .execute(update_data)
)

print(stats)

returns

{'num_inserted_rows': 1, 'num_updated_rows': 5, 'num_deleted_rows': 0}

Summary by CodeRabbit

Summary by CodeRabbit

• New Features
  • Merge-insert operations now return detailed statistics, including counts of inserted, updated, and deleted rows.
• Bug Fixes
  • Tests updated to validate returned merge-insert statistics for accuracy.
• Documentation
  • Method documentation improved to reflect new return values and clarify merge operation results.
  • Added documentation for the new MergeStats interface detailing operation statistics.

[coderabbitai[bot]]

Walkthrough

This set of changes updates the merge-insert operation across Rust, Python, and Node.js bindings to propagate and return detailed statistics (number of inserted, updated, and deleted rows) from the underlying Rust implementation up to the Python and Node.js layers. The Rust trait and method signatures for merge-insert are modified to return a MergeStats struct with operation statistics, and this return value is passed through the FFI boundary to Python and Node.js. Corresponding Python and Node.js methods are updated to return these statistics. The Python and Node.js tests are also modified to assert on the returned statistics, ensuring correctness of the merge-insert behavior.

Changes

File(s)	Change Summary
rust/lancedb/src/table.rs, rust/lancedb/src/remote/table.rs, rust/lancedb/src/table/merge.rs	Updated merge_insert and execute methods to return MergeStats instead of (). Publicly re-exported MergeStats. Updated trait and impl signatures accordingly.
nodejs/src/merge.rs, nodejs/lancedb/merge.ts, nodejs/test/table.test.ts	Modified NativeMergeInsertBuilder::execute to return MergeStats. Updated Node.js MergeInsertBuilder.execute to return and propagate these stats. Added assertions in tests to verify returned statistics after merge-insert operations.
python/src/table.rs	Modified Table::execute_merge_insert to return a Python dictionary with merge statistics (inserted, updated, deleted) instead of an empty result.
python/python/lancedb/table.py	Updated LanceTable._do_merge and AsyncTable._do_merge to return the results of the underlying merge operations, passing through the statistics to the caller.
python/python/tests/docs/test_merge_insert.py	Modified tests to capture and assert the statistics returned from .execute() calls, verifying the counts of inserted, updated, and deleted rows after merge-insert operations.

Sequence Diagram(s)

sequenceDiagram
    participant PythonCaller
    participant LanceTable/AsyncTable
    participant RustPyTable
    participant RustTable
    participant MergeInsertBuilder

    PythonCaller->>LanceTable/AsyncTable: _do_merge(...)
    LanceTable/AsyncTable->>RustPyTable: execute_merge_insert(...)
    RustPyTable->>RustTable: merge_insert(...)
    RustTable->>MergeInsertBuilder: execute(...)
    MergeInsertBuilder->>RustTable: merge_insert(...)
    RustTable-->>MergeInsertBuilder: MergeStats
    MergeInsertBuilder-->>RustTable: MergeStats
    RustTable-->>RustPyTable: MergeStats
    RustPyTable-->>LanceTable/AsyncTable: {inserted, updated, deleted}
    LanceTable/AsyncTable-->>PythonCaller: {inserted, updated, deleted}

sequenceDiagram
    participant Test
    participant Table
    participant .execute()
    Test->>Table: .execute()
    Table-->>Test: stats = {inserted, updated, deleted}
    Test->>Test: assert stats['inserted'] == expected
    Test->>Test: assert stats['updated'] == expected
    Test->>Test: assert stats['deleted'] == expected

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[xaptronic]

Thanks for working on this. Since it was so simple, I went ahead any filled in the node implementation.

Thank you, glad to contribute.

[xaptronic]

(gah sorry, wrong button)