LEO - DB2's LEarning Optimizer

Summary: LEO, DB2's LEarning Optimizer, uses a feedback loop to repair cardinality estimates by comparing forecasts with actuals at each QEP step. Online or offline, incremental or batched, it updates costs and statistics across operators (joins, DISTINCT, GROUP BY) with low overhead and large potential gains. (summarized by gpt-5-nano on Feb 09 2026)

Paper ID: 8917
Venue: VLDB
Year: 2001
Pagerank: 0.00034385207
Overall Rank: 100 | 99.32%
DOI: -

Incoming Non-self Citations Over Time

Authors

1. Michael Stillger (Siebel Systems, Inc.)
2. Guy Lohman (IBM)
3. Volker Markl (IBM)
4. Mokhtar Kandil (IBM)

BibTeX Citation

@article{stillger_vldb01,
        title = {{LEO - DB2's LEarning Optimizer}},
        author = {Stillger, Michael and Lohman, Guy and Markl, Volker and Kandil, Mokhtar},
        journal = {PVLDB},
        series = {{VLDB} '01},
        year = {2001}
}

Incoming Citations (Sorted by Pagerank)

Showing 22 of 122 citing papers.

Rank	Citing Paper	Year	Venue	Pagerank
8,698	SkinnerMT: Parallelizing for Efficiency and Robustness in Adaptive Query Processing on Multicore Platforms	2023	VLDB	5.3830073e-05
8,783	Tiresias: Enabling Predictive Autonomous Storage and Indexing	2022	VLDB	5.3740362e-05
9,450	Engineering High-Performance Database Engines	2014	VLDB	5.2660195e-05
9,601	Low Rank Learning for Offline Query Optimization	2025	SIGMOD	5.2487799e-05
9,671	Detecting Attribute Dependencies from Query Feedback	2007	VLDB	5.238674e-05
9,756	Efficient Query Re-optimization with Judicious Subquery Selections	2023	SIGMOD	5.2258278e-05
9,793	Selectivity Estimation for Queries Containing Predicates over Set-Valued Attributes	2023	SIGMOD	5.2193018e-05
9,796	ROME: Robust Query Optimization via Parallel Multi-Plan Execution	2024	SIGMOD	5.21848e-05
9,920	Still Asking: How Good Are Query Optimizers, Really?	2025	VLDB	5.1955087e-05
9,958	A Practical Theory of Generalization in Selectivity Learning	2025	VLDB	5.1879626e-05
9,971	Athena: An Effective Learning-based Framework for Query Optimizer Performance Improvement	2025	SIGMOD	5.1845938e-05
9,986	Thriving in the No Man’s Land between Compilers and Databases	2019	CIDR	5.1832796e-05
10,016	Turbo-Charging SPJ Query Plans with Learned Physical Join Operator Selections	2022	VLDB	5.1764556e-05
10,028	PRICE: A Pretrained Model for Cross-Database Cardinality Estimation	2025	VLDB	5.1745962e-05
10,875	Data-Agnostic Cardinality Learning from Imperfect Workloads	2025	VLDB	5.093636e-05
11,466	Anser: Adaptive Information Sharing Framework of AnalyticDB	2023	VLDB	5.093636e-05
12,096	Capturing the Laws of (Data) Nature	2015	CIDR	5.093636e-05
12,254	DBMS Metrology: Measuring Query Time	2013	SIGMOD	5.093636e-05
12,486	Visualizing the robustness of query execution	2009	CIDR	5.093636e-05
12,829	Adaptive Distributed Query Processing	2003	VLDB	5.093636e-05
12,846	SMART: Making DB2 (More) Autonomic	2002	VLDB	5.093636e-05
13,857	Automated Statistics Collection in Action	2005	SIGMOD	-

Outgoing Citations (Sorted by Pagerank)

Showing 11 of 11 cited papers.

Citations counted here include only citations to other VLDB/SIGMOD/CIDR/PODS papers in this database.

Rank	Cited Paper	Year	Venue	Pagerank
1	Access Path Selection in a Relational Database Management System	1979	SIGMOD	0.0024089429
35	Improved Histograms for Selectivity Estimation of Range Predicates	1996	SIGMOD	0.00048481081
89	On the Propagation of Errors in the Size of Join Results	1991	SIGMOD	0.00035031529
101	Selectivity Estimation Without the Attribute Value Independence Assumption	1997	VLDB	0.00034376651
151	Efficient Mid-Query Re-Optimization of Sub-Optimal Query Execution Plans	1998	SIGMOD	0.00029161879
222	Adaptive Selectivity Estimation Using Query Feedback	1994	SIGMOD	0.00024193708
235	Fast Incremental Maintenance of Approximate Histograms	1997	VLDB	0.00023783792
419	Cost-based Query Scrambling for Initial Delays	1998	SIGMOD	0.0001879684
448	Self-tuning Histograms: Building Histograms Without Looking at Data	1999	SIGMOD	0.00018292618
934	Selectivity Estimation and Query Optimization in Large Databases with Highly Skewed Distributions of Column Values	1988	VLDB	0.00013108714
2,984	Multiple Join Size Estimation by Virtual Domains (extended abstract)	1993	PODS	7.8920597e-05

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1	829	Proactive Re-Optimization	2005	SIGMOD
2	1,256	Sampling-Based Query Re-Optimization	2016	SIGMOD
3	5,701	Lemo: A Cache-Enhanced Learned Optimizer for Concurrent Queries	2023	SIGMOD
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5	6,543	Speeding Up End-to-end Query Execution via Learning-based Progressive Cardinality Estimation	2023	SIGMOD
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10	8,125	Learning Table Access Cardinalities with LEO	2002	SIGMOD