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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
0.00034099838
Overall Rank
98 | 99.35%
DOI
-

Incoming Non-self Citations Over Time

Authors

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
15 How Good Are Query Optimizers, Really? 2016 VLDB 0.00061067652
144 Neo: A Learned Query Optimizer 2019 VLDB 0.00029090793
160 CORDS: Automatic Discovery of Correlations and Soft Functional Dependencies 2004 SIGMOD 0.00027827605
255 The History of Histograms (abridged) 2003 VLDB 0.00022974524
361 Bao: Making Learned Query Optimization Practical 2021 SIGMOD 0.00020000855
406 Deep Unsupervised Cardinality Estimation 2020 VLDB 0.00019050182
471 Robust Query Processing through Progressive Optimization 2004 SIGMOD 0.00017744392
510 NeuroCard: One Cardinality Estimator for All Tables 2021 VLDB 0.00017059914
560 Plan-Structured Deep Neural Network Models for Query Performance Prediction 2019 VLDB 0.00016408613
644 Exploiting Statistics on Query Expressions for Optimization 2002 SIGMOD 0.00015209065
682 Robust Estimation of Resource Consumption for SQL Queries using Statistical Techniques 2012 VLDB 0.00014814858
688 Cardinality Estimation Done Right: Index-Based Join Sampling 2017 CIDR 0.00014749318
691 Selectivity Estimation for Range Predicates using Lightweight Models 2019 VLDB 0.00014737455
781 Self-tuning Database Technology and Information Services: from Wishful Thinking to Viable Engineering 2002 VLDB 0.00014019939
827 Adaptive Ordering of Pipelined Stream Filters 2004 SIGMOD 0.00013629035
981 Cardinality Estimation in DBMS: A Comprehensive Benchmark Evaluation 2022 VLDB 0.00012713454
995 Analyzing Plan Diagrams of Database Query Optimizers 2005 VLDB 0.00012629969
1,155 QuickSel: Quick Selectivity Learning with Mixture Models 2020 SIGMOD 0.00011777046
1,158 Toward a Progress Indicator for Database Queries 2004 SIGMOD 0.00011767292
1,244 Compressing SQL Workloads 2002 SIGMOD 0.00011369155
1,258 Sampling-Based Query Re-Optimization 2016 SIGMOD 0.00011308863
1,280 AI Meets AI: Leveraging Query Executions to Improve Index Recommendations 2019 SIGMOD 0.00011224914
1,432 Towards a Learning Optimizer for Shared Clouds 2019 VLDB 0.00010676754
1,588 Estimating Progress of Execution for SQL Queries 2004 SIGMOD 0.00010137374
1,605 SkinnerDB: Regret-Bounded Query Evaluation via Reinforcement Learning 2019 SIGMOD 0.00010095581
1,607 The Picasso Database Query Optimizer Visualizer 2010 VLDB 0.00010085995
1,663 BHUNT: Automatic Discovery of Fuzzy Algebraic Constraints in Relational Data 2003 VLDB 9.942673e-05
1,800 SkinnerDB: Regret-Bounded Query Evaluation via Reinforcement Learning 2018 VLDB 9.6082185e-05
1,890 WeTune: Automatic Discovery and Verification of Query Rewrite Rules 2022 SIGMOD 9.4234723e-05
1,931 Consistently Estimating the Selectivity of Conjuncts of Predicates 2005 VLDB 9.3511556e-05
1,989 Plan Bouquets: Query Processing without Selectivity Estimation 2014 SIGMOD 9.2469024e-05
2,002 FLAT: Fast, Lightweight and Accurate Method for Cardinality Estimation 2021 VLDB 9.2076835e-05
2,142 SASH: A Self-Adaptive Histogram Set for Dynamically Changing Workloads 2003 VLDB 8.9644817e-05
2,174 A Black-Box Approach to Query Cardinality Estimation 2007 CIDR 8.9193253e-05
2,217 Estimating Join Selectivities using Bandwidth-Optimized Kernel Density Models 2017 VLDB 8.8151982e-05
2,278 Active Learning for ML Enhanced Database Systems 2020 SIGMOD 8.7057608e-05
2,294 GORDIAN: Efficient and Scalable Discovery of Composite Keys 2006 VLDB 8.6831732e-05
2,583 Fauce: Fast and Accurate Deep Ensembles with Uncertainty for Cardinality Estimation 2021 VLDB 8.2589842e-05
2,625 Statistical Learning Techniques for Costing XML Queries 2005 VLDB 8.206615e-05
2,833 Cost Models for Big Data Query Processing: Learning, Retrofitting, and Our Findings 2020 SIGMOD 7.9539771e-05
2,844 FactorJoin: A New Cardinality Estimation Framework for Join Queries 2023 SIGMOD 7.9446987e-05
2,890 Query Optimizers: Time to Rethink the Contract? 2009 SIGMOD 7.9010819e-05
2,956 Scalable and Adaptive Online Joins 2014 VLDB 7.8100535e-05
2,963 Proving Query Equivalence Using Linear Integer Arithmetic 2023 SIGMOD 7.8035846e-05
2,989 Adapting to Source Properties in Processing Data Integration Queries 2004 SIGMOD 7.7736772e-05
3,053 A Unified Deep Model of Learning from both Data and Queries for Cardinality Estimation 2021 SIGMOD 7.7041081e-05
3,057 Towards a Hands-Free Query Optimizer through Deep Learning 2019 CIDR 7.6960881e-05
3,258 How to Fit when No One Size Fits 2013 CIDR 7.4839611e-05
3,327 Robust Query Driven Cardinality Estimation under Changing Workloads 2023 VLDB 7.4233639e-05
3,361 Conditional Selectivity for Statistics on Query Expressions 2004 SIGMOD 7.3726415e-05
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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 0.0023943337
37 Improved Histograms for Selectivity Estimation of Range Predicates 1996 SIGMOD 0.0004772731
91 On the Propagation of Errors in the Size of Join Results 1991 SIGMOD 0.00034748721
103 Selectivity Estimation Without the Attribute Value Independence Assumption 1997 VLDB 0.00033884854
149 Efficient Mid-Query Re-Optimization of Sub-Optimal Query Execution Plans 1998 SIGMOD 0.00028977821
232 Adaptive Selectivity Estimation Using Query Feedback 1994 SIGMOD 0.0002378554
242 Fast Incremental Maintenance of Approximate Histograms 1997 VLDB 0.00023354266
423 Cost-based Query Scrambling for Initial Delays 1998 SIGMOD 0.00018487497
454 Self-tuning Histograms: Building Histograms Without Looking at Data 1999 SIGMOD 0.00017955913
955 Selectivity Estimation and Query Optimization in Large Databases with Highly Skewed Distributions of Column Values 1988 VLDB 0.0001286095
3,000 Multiple Join Size Estimation by Virtual Domains (extended abstract) 1993 PODS 7.7657164e-05
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