Пусть полежит
https://db.in.tum.de/~freitag/papers/p1891-freitag.pdf
Цитата: "However, we also observe that the superior scaling behavior of worst-case optimal joins does not necessarily translate to an actual runtime advantage. If there are few distinct values r or duplicates d in the query result, binary join plans still exhibit reasonable performance and commonly outperform worst-case optimal joins. In these cases, the additional time required by a hash trie join for materializing all input relations in hash tries exceeds the time saved by its more efficient join evaluation. Consequently, the break-even point at which worst-case optimal joins begin to outperform binary join plans moves towards a smaller number of duplicates d as the number of distinct values r in the query result is increased. That is, worst-case optimal joins offer the greatest benefit on join queries where most tuples from the base relations have a large number of join partners."
Я этой штукой внимательно интересуюсь, поскольку внутри columnstore реализовано приближение к этому идеалу.
Цитата: "However, we also observe that the superior scaling behavior of worst-case optimal joins does not necessarily translate to an actual runtime advantage. If there are few distinct values r or duplicates d in the query result, binary join plans still exhibit reasonable performance and commonly outperform worst-case optimal joins. In these cases, the additional time required by a hash trie join for materializing all input relations in hash tries exceeds the time saved by its more efficient join evaluation. Consequently, the break-even point at which worst-case optimal joins begin to outperform binary join plans moves towards a smaller number of duplicates d as the number of distinct values r in the query result is increased. That is, worst-case optimal joins offer the greatest benefit on join queries where most tuples from the base relations have a large number of join partners."
Я этой штукой внимательно интересуюсь, поскольку внутри columnstore реализовано приближение к этому идеалу.