docs/source/user_guide/snapshot.rst

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.. Ported from the Paimon documentation:
.. https://github.com/apache/paimon/blob/master/docs/content/concepts/spec/snapshot.md

Snapshot
========

Direct file-system commits publish snapshot files with consecutive snapshot ids
starting from 1. The layout and hint files below describe those published files.
``EARLIEST`` and ``LATEST`` are hint files at the beginning and end of the snapshot list, and they can be inaccurate.
When hint files are inaccurate, the reader will scan all snapshot files to determine the beginning and end.

A catalog that manages table versions can hold the latest snapshot without a
snapshot file under the table path. Publication then depends on catalog
acceptance. ``UseRESTCatalogCommit(true)`` only prepares the request for the
caller to send; it does not publish a snapshot. See :doc:`commit` and
:doc:`catalog` for these modes and their historical metadata requirements.

Directory Layout
----------------

.. code-block:: shell

   warehouse
   └── default.db
       └── my_table
           ├── snapshot
               ├── EARLIEST
               ├── LATEST
               ├── snapshot-1
               ├── snapshot-2
               └── snapshot-3

A direct file-system commit attempts to publish the next snapshot id. Once the
snapshot file is successfully published, the commit becomes visible.

Snapshot File
-------------

Snapshot file is JSON and includes:

1. ``version``: Snapshot file version, current is 3.
2. ``uuid``: Uuid of this snapshot, generated on the client when the snapshot is created and absent only for a snapshot written before uuid was introduced. A commit names the uuid of the snapshot it is based on, so that a catalog can refuse a commit which raced another.
3. ``id``: Snapshot id, same as the file name.
4. ``schemaId``: The corresponding schema version for this commit.
5. ``baseManifestList``: A manifest list recording all changes from the previous snapshots.
6. ``baseManifestListSize``: Size in bytes of the base manifest list; optional.
7. ``deltaManifestList``: A manifest list recording all new changes occurred in this snapshot.
8. ``deltaManifestListSize``: Size in bytes of the delta manifest list; optional.
9. ``changelogManifestList``: A manifest list recording all changelog produced in this snapshot; omitted by C++ serialization if unset.
10. ``changelogManifestListSize``: Size in bytes of the changelog manifest list; optional.
11. ``indexManifest``: A manifest recording all index files of this table; omitted by C++ serialization if unset.
12. ``commitUser``: Usually generated by UUID; used for recovery of streaming writes—one stream write job with one user.
13. ``commitIdentifier``: Transaction id corresponding to streaming write; each transaction may result in multiple commits for different ``commitKind`` values.
14. ``commitKind``: Type of changes in this snapshot, including ``append``, ``compact``, ``overwrite`` and ``analyze``.
15. ``timeMillis``: Commit time in milliseconds.
16. ``totalRecordCount``: Record count of all changes occurred in this snapshot.
17. ``deltaRecordCount``: Record count of all new changes occurred in this snapshot.
18. ``changelogRecordCount``: Record count of all changelog produced in this snapshot; optional.
19. ``watermark``: Watermark for input records. When unset, C++ serialization omits this field.
    A commit carries forward the previous snapshot's watermark if no new watermark is supplied.
20. ``statistics``: Stats file name for statistics of this table; optional.
21. ``properties``: Optional string-to-string map of snapshot properties, including real-time progress metadata when enabled.
22. ``nextRowId``: Next row id for row tracking; optional.

The C++ snapshot serializer does not emit ``logOffsets``.