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a0e79f391f
When `BatchWriteItem` operates on multiple items sharing the same partition key in `always_use_lwt` write isolation mode, all CDC log entries are emitted under a single timestamp. The previous `get_records` parsing algorithm in `alternator/streams.cc` assumed that all CDC log entries sharing the same timestamp correspond to a single DynamoDB item change. As a result, it would incorrectly squash multiple distinct item changes into a single Streams record — producing wrong event data (e.g., one INSERT instead of four, with mismatched key/attribute values). Note: the bug is specific to `always_use_lwt` mode because only in LWT mode does the entire batch share a single timestamp. In non-LWT modes, each item in the batch receives a separate timestamp, so the entries naturally stay separate. **Commit 1: alternator: add BatchWriteItem Streams test** - Adds new tests `test_streams_batchwrite_no_clustering_deletes_non_existing_items` and `test_streams_batchwrite_no_clustering_deletes_existing_items` that cover the corner cases of batch-deleting a existing and non-existing item in a table without a clustering key. CDC tables without clustering keys are handled differently, and this path was previously untested for delete operations. - Adds a new test `test_streams_batchwrite_into_the_same_partition_will_report_wrong_stream_data`, that is a simple way to trigger a bug. - Adds a new test `test_streams_batchwrite_into_the_same_partition_deletes_existing_items`, that validates various combinations of puts and deletes in a single BatchWrite against the same partition. - Adds a new `test_table_ss_new_and_old_images_write_isolation_always` fixture and extends `create_table_ss` to accept `additional_tags`, enabling tests with a specific write isolation mode. **Commit 2: alternator: fix BatchWriteItem squashed Streams entries** The core fix rewrites the CDC log entry parsing in `get_records` to distinguish items by their clustering key: - Introduces `managed_bytes_ptr_hash` and `managed_bytes_ptr_equal` helper structs for pointer-based hash map lookups on `managed_bytes`. - Replaces the single `record`/`dynamodb` pair with a `std::unordered_map<const managed_bytes*, Record, ...>` (`records_map`) keyed by the base table's clustering key value from each CDC log row. For tables without a clustering key, all entries map to a single sentinel key. - Adds a validation that Alternator tables have at most one clustering key column (as required by the DynamoDB data model). - On end-of-record (`eor`), flushes all accumulated per-clustering-key records into the output, each with a unique `eventID` (the `event_id` format now includes an index suffix). - Adjusts the limit check: since a single CDC timestamp bucket can now produce multiple output records, the limit may be slightly exceeded to avoid breaking mid-batch. Fixes #28439 Fixes: SCYLLADB-540 Closes scylladb/scylladb#28452 * github.com:scylladb/scylladb: alternator/test: explain why 'always' write isolation mode is used in tests alternator/test: add scylla_only to always write isolation fixture alternator: fix BatchWriteItem squashed Streams entries alternator: add BatchWriteItem test (failing)