How Good Are Query Optimizers, Really?¶
Leis, V., Gubichev, A., Mirchev, A., Boncz, P., Kemper, A., & Neumann, T. (2015). How Good Are Query Optimizers, Really?. Proceedings of the VLDB Endowment, 9(3), 204-215.
Cited by¶
2 citations across 2 artifacts.
Each citation links to the sentence it supports in the citing article.
Mechanisms¶
- Query-Plan Lowering and Optimization
- A wrong row-count guess can pick a plan orders of magnitude worse than the naive one, and the failure is silent — the answer is right, just slow.
This sourceShows that cardinality misestimates can select semantically equivalent query plans that return correct results but run orders of magnitude more slowly.
- A wrong row-count guess can pick a plan orders of magnitude worse than the naive one, and the failure is silent — the answer is right, just slow.
- Query Plan Rewriter
- Its fragility is that everything rests on estimated cardinalities, and estimation error compounds through a multi-join plan, so a single bad guess (a skewed column, correlated predicates the model assumes independent) can select a catastrophically slow plan with total confidence.
This sourceShows that cardinality-estimation errors caused by simplifying independence assumptions can compound across multi-join queries and lead an optimizer to choose disastrously slow plans.
- Its fragility is that everything rests on estimated cardinalities, and estimation error compounds through a multi-join plan, so a single bad guess (a skewed column, correlated predicates the model assumes independent) can select a catastrophically slow plan with total confidence.
Verification¶
Does it exist? Confirmed. This work's DOI resolves to a registered record, which fixes its identity. That is all it fixes.
Does it back the claim? Not recorded. Neither this nor any other of the 2 citations of this work carries a recorded support check.
Support is checked per citation rather than per work — the same source can be cited soundly in one article and wrongly in another. Per-citation recording began recently, so a citation with no recorded check is a gap in the record rather than evidence it went unchecked.
See how references were verified.
Registry ID ref:9c0dac99f4e0 · see in the full table