CASSANDRA-19661: Dynamically skip sharding L0 when SAI Vector index present#4605
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michaeljmarshall wants to merge 3 commits intoapache:cassandra-5.0from
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CASSANDRA-19661: Dynamically skip sharding L0 when SAI Vector index present#4605michaeljmarshall wants to merge 3 commits intoapache:cassandra-5.0from
michaeljmarshall wants to merge 3 commits intoapache:cassandra-5.0from
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netudima
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Feb 10, 2026
src/java/org/apache/cassandra/db/compaction/UnifiedCompactionStrategy.java
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(cherry picked from commit 94406f3)
netudima
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Feb 17, 2026
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This is a partial solution to https://issues.apache.org/jira/browse/CASSANDRA-19661. It works by using a single shard at L0 when a vector index is present. As noted in the jira ticket, there are edge cases that may still produce errors, notably the case where there are multiple data directories.
The key trade offs here are related to the time complexity for search. Since graph search is
log(n), and searching m graphs ism * log(n), we see better search performance by building bigger graphs which is essentiallylog(m * n). We could pre-shard, which comes at a cost of increased search time complexity.