Files
scylladb/test
Radosław Cybulski 6e5aaa85b6 alternator: fix Alternator writing unnecesary cdc entries
Work in this patch is a result of two bugs - spurious MODIFY event, when
remove column is used in `update_item` on non-existing item and
spurious events, when batch write item mixed noop operations with
operations involving actual changes (the former would still emit
cdc log entries).
The latter issue required rework of Piotr Wieczorek's algorithm,
which fixed former issue as well.

Piotr Wieczorek previously wrote checks, that should
prevent unnecesary cdc events from being written. His implementation
missed the fact, that a single `mutation` object passed to cdc code
to be analysed for cdc log entries can contain modifications for
multiple rows (with the same timestamp - for example as a result
to BatchWriteItem call). His code tries to skip whole `mutation`,
which in such case is not possible, because BatchWriteItem might have
one item that does nothing and second item that does modification
(this is the reason for the second bug).

His algorithm was extended and moved. Originally it was working
as follows - user would sent a `mutation` object with some changes to
be "augmented". The cdc would process those changes and built a set of
cdc log changes based on them, that would be added to cdc log table.
Piotr added a `should_skip` function, which processes user changes and
tried to determine if they all should be dropped or not.
New version, instead of trying to skip adding rows to
cdc log `mutation` object, builds a rows-to-ignore set.
After whole cdc log `mutation` object is completed, it processes it
and go through it row by row. Any row that was previously added to
a `rows_to_ignore` set will now be removed. Remaining rows are written to
new cdc log `mutation` with new clustering key
(`cdc$batch_seq_no` index value should probably be consecutive -
we just want to be safe here) and returns new `mutation` object to
be sent to cdc log table.

The first bug is fixed as a side effect of new algorithm,
which contains more precise checks detecting, if given
mutation actually made a difference.

Fixes: #28368
Fixes: SCYLLADB-538
Fixes: SCYLLADB-1528
Refs: #28452
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Scylla in-source tests.

For details on how to run the tests, see docs/dev/testing.md

Shared C++ utils, libraries are in lib/, for Python - pylib/

alternator - Python tests which connect to a single server and use the DynamoDB API unit, boost, raft - unit tests in C++ cqlpy - Python tests which connect to a single server and use CQL topology* - tests that set up clusters and add/remove nodes cql - approval tests that use CQL and pre-recorded output rest_api - tests for Scylla REST API Port 9000 scylla-gdb - tests for scylla-gdb.py helper script nodetool - tests for C++ implementation of nodetool

If you can use an existing folder, consider adding your test to it. New folders should be used for new large categories/subsystems, or when the test environment is significantly different from some existing suite, e.g. you plan to start scylladb with different configuration, and you intend to add many tests and would like them to reuse an existing Scylla cluster (clusters can be reused for tests within the same folder).

To add a new folder, create a new directory, and then copy & edit its suite.ini.