> whether this would really work out in most workloads > just because it keeps the cache-lines hotter and less likely to be evicted. Okay, so keeping cache fo

> whether this would really work out in most workloads > just because it keeps the cache-lines hotter and less likely to be evicted. Okay, so keeping cache for a bloom filter problem is real - but the real force evicting memory out of the cache line is the next row-group you read + all the other stuff you have to do when you implement this in a database product. Memory bandwidth is contested heavily and the caches will get knocked out every 1024 rows. So the two things I work with, Apache Hive and Apache Impala switched to a blocked bloom filter at different points in time. Hive BloomKFilter - https://github.com/apache/hive/blob/master/storage-api/src/java/org/apache/hive/common/util/BloomKFilter.java#L35 https://github.com/apache/hive/blob/master/storage-api/src/j... Impala/Kudu one - https://github.com/apache/impala/blob/master/be/src/kudu/util/block_bloom_filter.h#L66 https://github.com/apache/impala/blob/master/be/src/kudu/uti... The C++ one also has an AVX specialization, while the Java one relies on the JVM to do it (not always) - https://github.com/apache/impala/blob/master/be/src/kudu/util/block_bloom_filter_avx2.cc#L72 https://github.com/apache/impala/blob/master/be/src/kudu/uti... We ran a lot of trivial benchmarks and several benchmarks where the shuffle-join+network (not sort-merge, this is just a partitioned hash join) generates a bloom filter (a semijoin) before sending rows out and the 1-cache line version won out when the bloom filter went slightly over the 1 Million + 5% rate [1]. The regular bloom filter went from (38ns -> 108ns for 1k -> 1m items), while the BloomK stuck at (27ns) despite making room for a million times more items in the bloom. The bloom-1 (which is the 64bit version) underperformed on accuracy (was ~2x faster at 16ns per op, but worse at filtering out items). [1] - https://github.com/prasanthj/bloomfilter/tree/master/benchmarks https://github.com/prasanthj/bloomfilter/tree/master/benchma...