Github user jianqiao commented on the issue:
https://github.com/apache/incubator-quickstep/pull/300
@zuyu Currently `HashJoinOperator` performance is sensitive to the _number
of build blocks per probe block_ due to the concurrency bottleneck within LRU
policy enforcer.
Consider the situation that the build side relation has `N` blocks and the
number of blocks decreases to `M` after applying the predicate, where `N` is
very large but `M` is small. Then materializing the filtered build-side
relation incurs only a small overhead, but it dramatically reduces the _number
of build blocks per probe block_.
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