Michael Semb Wever created CASSANDRA-21700:
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Summary: Index hints serialization rejects a count that the
validation accepts
Key: CASSANDRA-21700
URL: https://issues.apache.org/jira/browse/CASSANDRA-21700
Project: Apache Cassandra
Issue Type: Bug
Components: Feature/2i Index
Reporter: Michael Semb Wever
{{IndexHints.fromCQLNames}} rejects a count above the maximum:
{code:java}
if (included != null && included.size() > maxIncludedOrExcludedIndexCount())
throw new InvalidRequestException(TOO_MANY_INDEXES_ERROR + included.size());
{code}
so a {{SELECT}} may name exactly {{maxIncludedOrExcludedIndexCount()}} included
or excluded indexes. The serializer then asserted a count strictly below the
same maximum:
{code:java}
assert n < maxIncludedOrExcludedIndexCount() : TOO_MANY_INDEXES_ERROR + n;
{code}
The two disagree at the boundary. A query that names the maximum passes
validation on the coordinator and then throws an {{AssertionError}} when the
read command is serialized for a replica, and the daemon runs with assertions
enabled. An operator meets this by setting
{{secondary_indexes_per_table_fail_threshold}} to N and naming N indexes, or by
naming 128 indexes when that guardrail is unset.
The patch relaxes the assertion to {{<=}}, and makes
{{maxIncludedOrExcludedIndexCount()}} package-private so the test can read the
same limit. The count is written with {{writeVInt32}}, so the boundary carries
no on-the-wire risk.
Patch:
[mck/upstream/index-hints-limit-off-by-one/trunk|https://github.com/thelastpickle/cassandra/tree/mck/upstream/index-hints-limit-off-by-one/trunk]
Provenance:
[d29e4a67f7|https://github.com/datastax/cassandra/commit/d29e4a67f76d2c812f2a3a283910876797ff2f9c]
by [~brandon.williams]. That commit makes the same one-character change, and
also ignores an {{UnknownIndexException}} during deserialization so a hint for
an index that has not yet propagated is dropped rather than failing the read.
This patch leaves that part out, because silently dropping a hint changes what
the query does and needs its own discussion. That commit carries no test; this
patch adds one.
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