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: h4d27b9e0c3a031e3
Venue: VLDB
Year: 2001
Pagerank: 0.00034106982
Overall Rank: 98 | 99.35%
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 50 of 123 citing papers.

Rank	Citing Paper	Year	Venue	Pagerank
3,367	Exact Cardinality Query Optimization for Optimizer Testing	2009	VLDB	7.3719456e-05
3,446	Apache Hive: From MapReduce to Enterprise-grade Big Data Warehousing	2019	SIGMOD	7.2942885e-05
3,527	Identifying Robust Plans through Plan Diagram Reduction	2008	VLDB	7.2310714e-05
3,545	Computation Reuse in Analytics Job Service at Microsoft	2018	SIGMOD	7.2134803e-05
3,584	Lazy, Adaptive RID-List Intersection, and Its Application to Index Anding	2007	SIGMOD	7.1896153e-05
3,590	Make Your Database System Dream of Electric Sheep: Towards Self-Driving Operation	2021	VLDB	7.1865343e-05
3,592	Looking Ahead Makes Query Plans Robust: Making the Initial Case with In-Memory Star Schema Data Warehouse Workloads	2017	VLDB	7.1835842e-05
3,884	FiGO: Fine-Grained Query Optimization in Video Analytics	2022	SIGMOD	6.948464e-05
4,045	Adaptive Query Processing in the Looking Glass	2005	CIDR	6.8328968e-05
4,106	Content-Based Routing: Different Plans for Different Data	2005	VLDB	6.8032891e-05
4,234	Adaptive Statistics in Oracle 12c	2017	VLDB	6.7134191e-05
4,252	Primitives for Workload Summarization and Implications for SQL	2003	VLDB	6.7015609e-05
4,267	Buffer Pool Aware Query Optimization	2005	CIDR	6.6967071e-05
4,311	ALECE: An Attention-based Learned Cardinality Estimator for SPJ Queries on Dynamic Workloads	2024	VLDB	6.6727978e-05
4,506	Xplus: A SQL-Tuning-Aware Query Optimizer	2010	VLDB	6.5726463e-05
4,657	On the Production of Anorexic Plan Diagrams	2007	VLDB	6.4824233e-05
4,659	Automated Statistics Collection in DB2 UDB	2004	VLDB	6.4822228e-05
4,707	PreQR: Pre-training Representation for SQL Understanding	2022	SIGMOD	6.4587914e-05
4,793	Permutable Compiled Queries: Dynamically Adapting Compiled Queries without Recompiling	2021	VLDB	6.4127583e-05
4,818	Continuous Cloud-Scale Query Optimization and Processing	2013	VLDB	6.3964573e-05
4,893	A Characterization of the Sensitivity of Query Optimization to Storage Access Cost Parameters	2003	SIGMOD	6.3677985e-05
5,041	LSched: A Workload-Aware Learned Query Scheduler for Analytical Database Systems	2022	SIGMOD	6.3006152e-05
5,044	Lightweight Cardinality Estimation in LSM-based Systems	2018	SIGMOD	6.30014e-05
5,241	FASTgres: Making Learned Query Optimizer Hinting Effective	2023	VLDB	6.2154384e-05
5,348	Adaptive and Robust Query Execution for Lakehouses at Scale	2024	VLDB	6.1690434e-05
5,386	PREDIcT: Towards Predicting the Runtime of Large Scale Iterative Analytics	2013	VLDB	6.1522468e-05
5,470	A Pay-As-You-Go Framework for Query Execution Feedback	2008	VLDB	6.1182634e-05
5,569	Exploring Change – A New Dimension of Data Analytics	2019	VLDB	6.0813343e-05
5,597	StatAdvisor: Recommending Statistical Views	2009	VLDB	6.0718206e-05
5,777	POP/FED: Progressive Query Optimization for Federated Queries in DB2	2006	VLDB	5.9981204e-05
5,871	PilotScope: Steering Databases with Machine Learning Drivers	2024	VLDB	5.9639223e-05
5,922	Inspector Joins	2005	VLDB	5.9469659e-05
5,973	Understanding Cardinality Estimation using Entropy Maximization	2010	PODS	5.9306716e-05
5,974	Towards instance-optimized data systems	2021	VLDB	5.9305575e-05
5,988	On the Stability of Plan Costs and the Costs of Plan Stability	2010	VLDB	5.9257426e-05
6,141	Expand your Training Limits! Generating Training Data for ML-based Data Management	2021	SIGMOD	5.8733296e-05
6,241	Operator and Query Progress Estimation in Microsoft SQL Server Live Query Statistics	2016	SIGMOD	5.8381762e-05
6,441	Grizzly: Efficient Stream Processing Through Adaptive Query Compilation	2020	SIGMOD	5.7834762e-05
6,660	Speeding Up End-to-end Query Execution via Learning-based Progressive Cardinality Estimation	2023	SIGMOD	5.7178404e-05
6,791	dbET: Execution Time Distribution-based Plan Selection	2023	SIGMOD	5.6811782e-05
7,072	Plan Stitch: Harnessing the Best of Many Plans	2018	VLDB	5.6074688e-05
7,249	Efficient Adaptive Detection of Complex Event Patterns	2018	VLDB	5.5745603e-05
7,410	POLAR: Adaptive and Non-invasive Join Order Selection via Plans of Least Resistance	2024	VLDB	5.5342768e-05
7,460	T3: Accurate and Fast Performance Prediction for Relational Database Systems With Compiled Decision Trees	2025	SIGMOD	5.5215755e-05
7,487	Non-Invasive Progressive Optimization for In-Memory Databases	2016	VLDB	5.5119239e-05
7,597	On the Calculation of Optimality Ranges for Relational Query Execution Plans	2018	SIGMOD	5.4872821e-05
7,633	Consistent Histograms In The Presence of Distinct Value Counts	2009	VLDB	5.4792473e-05
8,131	Thrifty Query Execution via Incrementability	2020	SIGMOD	5.3936608e-05
8,164	Efficient Query Re-optimization with Judicious Subquery Selections	2023	SIGMOD	5.3852872e-05
8,288	Learning Table Access Cardinalities with LEO	2002	SIGMOD	5.3614914e-05

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	0.0023947656
37	Improved Histograms for Selectivity Estimation of Range Predicates	1996	SIGMOD	0.00047731453
91	On the Propagation of Errors in the Size of Join Results	1991	SIGMOD	0.0003475226
103	Selectivity Estimation Without the Attribute Value Independence Assumption	1997	VLDB	0.00033894985
149	Efficient Mid-Query Re-Optimization of Sub-Optimal Query Execution Plans	1998	SIGMOD	0.00028981723
232	Adaptive Selectivity Estimation Using Query Feedback	1994	SIGMOD	0.00023792809
242	Fast Incremental Maintenance of Approximate Histograms	1997	VLDB	0.00023363722
424	Cost-based Query Scrambling for Initial Delays	1998	SIGMOD	0.0001848836
454	Self-tuning Histograms: Building Histograms Without Looking at Data	1999	SIGMOD	0.00017962189
956	Selectivity Estimation and Query Optimization in Large Databases with Highly Skewed Distributions of Column Values	1988	VLDB	0.00012865801
3,005	Multiple Join Size Estimation by Virtual Domains (extended abstract)	1993	PODS	7.7621043e-05

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