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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
0.00034050614
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 0.00061463175
142 Neo: A Learned Query Optimizer 2019 VLDB 0.00029114937
160 CORDS: Automatic Discovery of Correlations and Soft Functional Dependencies 2004 SIGMOD 0.00027775994
254 The History of Histograms (abridged) 2003 VLDB 0.00022999992
355 Bao: Making Learned Query Optimization Practical 2021 SIGMOD 0.00020146245
405 Deep Unsupervised Cardinality Estimation 2020 VLDB 0.00019020138
471 Robust Query Processing through Progressive Optimization 2004 SIGMOD 0.00017691682
508 NeuroCard: One Cardinality Estimator for All Tables 2021 VLDB 0.00017108973
545 Plan-Structured Deep Neural Network Models for Query Performance Prediction 2019 VLDB 0.0001657599
646 Exploiting Statistics on Query Expressions for Optimization 2002 SIGMOD 0.00015166402
676 Robust Estimation of Resource Consumption for SQL Queries using Statistical Techniques 2012 VLDB 0.00014838681
689 Cardinality Estimation Done Right: Index-Based Join Sampling 2017 CIDR 0.00014725904
690 Selectivity Estimation for Range Predicates using Lightweight Models 2019 VLDB 0.00014703258
775 Self-tuning Database Technology and Information Services: from Wishful Thinking to Viable Engineering 2002 VLDB 0.00014062388
824 Adaptive Ordering of Pipelined Stream Filters 2004 SIGMOD 0.0001360282
983 Cardinality Estimation in DBMS: A Comprehensive Benchmark Evaluation 2022 VLDB 0.00012677179
996 Analyzing Plan Diagrams of Database Query Optimizers 2005 VLDB 0.00012595827
1,156 QuickSel: Quick Selectivity Learning with Mixture Models 2020 SIGMOD 0.00011759683
1,159 Toward a Progress Indicator for Database Queries 2004 SIGMOD 0.00011739527
1,246 Compressing SQL Workloads 2002 SIGMOD 0.00011355447
1,261 Sampling-Based Query Re-Optimization 2016 SIGMOD 0.00011289724
1,282 AI Meets AI: Leveraging Query Executions to Improve Index Recommendations 2019 SIGMOD 0.00011197535
1,436 Towards a Learning Optimizer for Shared Clouds 2019 VLDB 0.00010658836
1,587 Estimating Progress of Execution for SQL Queries 2004 SIGMOD 0.00010119368
1,604 The Picasso Database Query Optimizer Visualizer 2010 VLDB 0.00010086711
1,609 SkinnerDB: Regret-Bounded Query Evaluation via Reinforcement Learning 2019 SIGMOD 0.0001007196
1,670 BHUNT: Automatic Discovery of Fuzzy Algebraic Constraints in Relational Data 2003 VLDB 9.9124313e-05
1,803 SkinnerDB: Regret-Bounded Query Evaluation via Reinforcement Learning 2018 VLDB 9.5987229e-05
1,888 WeTune: Automatic Discovery and Verification of Query Rewrite Rules 2022 SIGMOD 9.4148912e-05
1,935 Consistently Estimating the Selectivity of Conjuncts of Predicates 2005 VLDB 9.3407959e-05
1,987 Plan Bouquets: Query Processing without Selectivity Estimation 2014 SIGMOD 9.2323722e-05
2,009 FLAT: Fast, Lightweight and Accurate Method for Cardinality Estimation 2021 VLDB 9.1813272e-05
2,154 SASH: A Self-Adaptive Histogram Set for Dynamically Changing Workloads 2003 VLDB 8.9382906e-05
2,174 A Black-Box Approach to Query Cardinality Estimation 2007 CIDR 8.9067128e-05
2,228 Estimating Join Selectivities using Bandwidth-Optimized Kernel Density Models 2017 VLDB 8.7912743e-05
2,290 Active Learning for ML Enhanced Database Systems 2020 SIGMOD 8.6813363e-05
2,305 GORDIAN: Efficient and Scalable Discovery of Composite Keys 2006 VLDB 8.6550507e-05
2,584 Fauce: Fast and Accurate Deep Ensembles with Uncertainty for Cardinality Estimation 2021 VLDB 8.2435322e-05
2,614 Statistical Learning Techniques for Costing XML Queries 2005 VLDB 8.2023561e-05
2,828 Cost Models for Big Data Query Processing: Learning, Retrofitting, and Our Findings 2020 SIGMOD 7.9476509e-05
2,852 FactorJoin: A New Cardinality Estimation Framework for Join Queries 2023 SIGMOD 7.9201312e-05
2,888 Query Optimizers: Time to Rethink the Contract? 2009 SIGMOD 7.8895201e-05
2,971 Proving Query Equivalence Using Linear Integer Arithmetic 2023 SIGMOD 7.7851336e-05
2,972 Scalable and Adaptive Online Joins 2014 VLDB 7.7844791e-05
3,001 Adapting to Source Properties in Processing Data Integration Queries 2004 SIGMOD 7.7492907e-05
3,060 A Unified Deep Model of Learning from both Data and Queries for Cardinality Estimation 2021 SIGMOD 7.6828463e-05
3,062 Towards a Hands-Free Query Optimizer through Deep Learning 2019 CIDR 7.6809918e-05
3,269 Robust Query Driven Cardinality Estimation under Changing Workloads 2023 VLDB 7.463682e-05
3,271 How to Fit when No One Size Fits 2013 CIDR 7.4609627e-05
3,361 Exact Cardinality Query Optimization for Optimizer Testing 2009 VLDB 7.3621595e-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 0.0023948467
37 Improved Histograms for Selectivity Estimation of Range Predicates 1996 SIGMOD 0.00047654188
91 On the Propagation of Errors in the Size of Join Results 1991 SIGMOD 0.00034691614
103 Selectivity Estimation Without the Attribute Value Independence Assumption 1997 VLDB 0.00033847446
149 Efficient Mid-Query Re-Optimization of Sub-Optimal Query Execution Plans 1998 SIGMOD 0.00028910892
234 Adaptive Selectivity Estimation Using Query Feedback 1994 SIGMOD 0.00023726296
242 Fast Incremental Maintenance of Approximate Histograms 1997 VLDB 0.00023327437
426 Cost-based Query Scrambling for Initial Delays 1998 SIGMOD 0.00018432573
457 Self-tuning Histograms: Building Histograms Without Looking at Data 1999 SIGMOD 0.00017915659
960 Selectivity Estimation and Query Optimization in Large Databases with Highly Skewed Distributions of Column Values 1988 VLDB 0.00012825107
3,009 Multiple Join Size Estimation by Virtual Domains (extended abstract) 1993 PODS 7.7439468e-05
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