Choose the right algorithm for your data. ClickHouse provides multiple join algorithms via the join_algorithm setting, each trading off memory usage against performance. Hash joins are fast but memory-bound. Grace hash partitions data into buckets and spills to disk when memory is exhausted. Sort-merge variants (partial_merge, full_sorting_merge) work well for pre-sorted data or when both sides are too large for memory. The direct algorithm acts as a fast key-value lookup when the right table is backed by a dictionary or a small in-memory table. Setting join_algorithm = 'auto' lets ClickHouse adaptively select the best algorithm at runtime based on available resources.
同事揭示尤拉·鲍里索夫的成功秘诀20:44
，这一点在snipaste截图中也有详细论述
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