* HyperLogLog? Convenient for doing approximate counting across huge datasets.
* SkipList is another probabilistic data structure that allows you to skip ahead N elements in 1 step. I believe ClickHouse uses it.
* Bitmap index organizes database pointers into a matrix of bits. The bitmap scans simply skip over the zeros. This type of index gets in trouble if you have high cardinality, though.
Lots of companies use skiplists without realizing it because Redis uses them as the implementation of sorted sets. For example, last time I checked, every time someone looks at a playlist on PornHub the software is doing a partial traversal of a skiplist behind the scenes.
* HyperLogLog? Convenient for doing approximate counting across huge datasets.
* SkipList is another probabilistic data structure that allows you to skip ahead N elements in 1 step. I believe ClickHouse uses it.
* Bitmap index organizes database pointers into a matrix of bits. The bitmap scans simply skip over the zeros. This type of index gets in trouble if you have high cardinality, though.