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Right? How do the folks at QuestDB know that their new JIT engine is actually responsible for those performance improvements? My understanding is that, index or not, data is still sorted by time in questdb, which is exactly what the ClickHouse engineers are replicating in the new schema.

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The query Clickhouse picked on does not actually leverage time order. Perhaps clickhouse vendors on this thread can comment on relevance of the date partitioning for this query. My best guess is that it might help the execution logic to create data chunks for parallel scan.

QuestDB does also use partitions for this purpose but we also calculate chunks dynamically based on available CPU to distribute load across cores more evenly

That's fair enough and I get the broader point about ClickHouse being rather inflexible wrt query performance. It still seems like the initial sorting key for CH would've been the worst possible one for all benchmark scenarios.

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