Piotr Dulikowski 44c605e59c Merge 'Fix the types of change events in Alternator Streams' from Piotr Wieczorek ...

This patch increases the compatibility with DynamoDB Streams by integrating the DynamoDB's event type rules (described in https://github.com/scylladb/scylladb/issues/6918) into Alternator. The main changes are:
- introduce a new flag `alternator_streams_strict_compatibility`, meant as a guard of performance-intensive operations that increase the compatibility with DynamoDB Streams. If enabled, Alternator always performs a RBW before a data-modifying operation, and propagates its result to CDC. Then, the old item is compared to the new one, to determine the mutation type (INSERT vs MODIFY). This option is a no-op for tables with disabled Alternator Streams,
- reduce splitting of simple Alternator mutations,
- correctly distinguish event types described in #6918, except for item deletes. Deleting a missing item with DeleteItem, BatchWriteItem, or a missing field with UpdateItem still emit REMOVEs.

To summarize, the emitted events of the data manipulation operations should be as follows:
- DeleteItem/BatchWriteItem.DeleteItem of existing item: REMOVE (OK)
- DeleteItem of nonexistent item: nothing (OK)
- BatchWriteItem.DeleteItem of nonexistent item: nothing (OK)
- PutItem/UpdateItem/BatchWriteItem.PutItem of existing and not equal item: MODIFY (OK)
- PutItem/UpdateItem/BatchWriteItem.PutItem of existing and equal item: nothing (OK)
- PutItem/UpdateItem/BatchWriteItem.PutItem of nonexistent item: INSERT (OK)

No backport is necessary.

Refs https://github.com/scylladb/scylladb/pull/26149
Refs https://github.com/scylladb/scylladb/pull/26396
Refs https://github.com/scylladb/scylladb/issues/26382
Fixes https://github.com/scylladb/scylladb/issues/6918

Closes scylladb/scylladb#26121

* github.com:scylladb/scylladb:
  test/alternator: Enable the tests failing because of #6918
  alternator, cdc: Don't emit events for no-op removes
  alternator, cdc: Don't emit an event for equal items
  alternator/streams, cdc: Differentiate item replace and item update in CDC
  alternator: Change the return type of rmw_operation_return
  config: Add alternator_streams_strict_compatibility flag
  cdc: Don't split a row marker away from row cells

2025-11-30 07:20:22 +01:00

317 KiB

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