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by ople 767 days ago
Very interesting observations! Merge performance tuning seems often overlooked even though it's a key aspect of sustained ClickHouse performance.

I also like that the blog is quite compact and gets the points across without getting too much into the weeds.

One thing I've noticed also that bloom filter index types can be quite costly to merge. In many cases that's acceptable though due to the massive benefit they provide for text queries. One just has to be mindful of the overhead when adding them.

1 comments

Exploring bloom filter index merges would be an interesting addition. I do wish it were easier to profile merge performance to break down where most of the CPU time is being spent.