Tag: olap
A side-by-side look at how ClickHouse and StarRocks use Bloom filters: granules vs pages, tunable vs automatic indexes, text search, join runtime filters, and how to verify each. Plus a decision guide for when to use what.
How StarRocks uses Bloom filters in two very different places: page-level indexes stored on disk, and runtime filters built during joins. How to create them, verify them in the query profile, and know when they won't help.
How ClickHouse uses Bloom filter skip indexes to avoid reading data, how to choose between bloom_filter, tokenbf_v1 and ngrambf_v1, how to size them, and how to tell whether they actually work.
A plain-language tour of StarRocks' storage hierarchy, from catalogs, partitions and tablets down to rowsets, segments and data pages, and how zone maps, bitmap indexes and bloom filters let queries skip most of the data without ever reading it.