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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
8727
Venue
VLDB
Year
2001
Pagerank
0.00034651834
Overall Rank
99 | 99.32%
DOI
-

Incoming Non-self Citations Over Time

Authors

Incoming Citations (Sorted by Pagerank)

Showing 50 of 122 citing papers.

Rank Citing Paper Year Venue Pagerank
20 How Good Are Query Optimizers, Really? 2016 VLDB 0.00058294381
157 Neo: A Learned Query Optimizer 2019 VLDB 0.00028782395
159 CORDS: Automatic Discovery of Correlations and Soft Functional Dependencies 2004 SIGMOD 0.00028420571
256 The History of Histograms (abridged) 2003 VLDB 0.00023353808
394 Bao: Making Learned Query Optimization Practical 2021 SIGMOD 0.00019400224
411 Deep Unsupervised Cardinality Estimation 2020 VLDB 0.00019014394
491 Robust Query Processing through Progressive Optimization 2004 SIGMOD 0.00017645668
524 NeuroCard: One Cardinality Estimator for All Tables 2021 VLDB 0.00017177356
560 Plan-Structured Deep Neural Network Models for Query Performance Prediction 2019 VLDB 0.00016570735
660 Exploiting Statistics on Query Expressions for Optimization 2002 SIGMOD 0.00015363874
690 Robust Estimation of Resource Consumption for SQL Queries using Statistical Techniques 2012 VLDB 0.00015080949
702 Cardinality Estimation Done Right: Index-Based Join Sampling 2017 CIDR 0.00014941084
715 Selectivity Estimation for Range Predicates using Lightweight Models 2019 VLDB 0.0001480646
764 Self-tuning Database Technology and Information Services: from Wishful Thinking to Viable Engineering 2002 VLDB 0.00014253508
795 Adaptive Ordering of Pipelined Stream Filters 2004 SIGMOD 0.00014006175
975 Analyzing Plan Diagrams of Database Query Optimizers 2005 VLDB 0.0001295619
1,122 Toward a Progress Indicator for Database Queries 2004 SIGMOD 0.00012174023
1,164 Cardinality Estimation in DBMS: A Comprehensive Benchmark Evaluation 2022 VLDB 0.00011978719
1,187 QuickSel: Quick Selectivity Learning with Mixture Models 2020 SIGMOD 0.00011849604
1,250 Sampling-Based Query Re-Optimization 2016 SIGMOD 0.00011563119
1,251 Compressing SQL Workloads 2002 SIGMOD 0.00011559835
1,280 AI Meets AI: Leveraging Query Executions to Improve Index Recommendations 2019 SIGMOD 0.0001144289
1,468 Towards a Learning Optimizer for Shared Clouds 2019 VLDB 0.00010750589
1,516 Estimating Progress of Execution for SQL Queries 2004 SIGMOD 0.00010573921
1,624 BHUNT: Automatic Discovery of Fuzzy Algebraic Constraints in Relational Data 2003 VLDB 0.00010256872
1,646 The Picasso Database Query Optimizer Visualizer 2010 VLDB 0.00010197566
1,711 SkinnerDB: Regret-Bounded Query Evaluation via Reinforcement Learning 2019 SIGMOD 0.00010036767
1,799 SkinnerDB: Regret-Bounded Query Evaluation via Reinforcement Learning 2018 VLDB 9.8203085e-05
1,942 Consistently Estimating the Selectivity of Conjuncts of Predicates 2005 VLDB 9.5209948e-05
1,976 FLAT: Fast, Lightweight and Accurate Method for Cardinality Estimation 2021 VLDB 9.4645971e-05
2,039 Plan Bouquets: Query Processing without Selectivity Estimation 2014 SIGMOD 9.3438044e-05
2,097 SASH: A Self-Adaptive Histogram Set for Dynamically Changing Workloads 2003 VLDB 9.242975e-05
2,123 WeTune: Automatic Discovery and Verification of Query Rewrite Rules 2022 SIGMOD 9.1909071e-05
2,144 A Black-Box Approach to Query Cardinality Estimation 2007 CIDR 9.1531391e-05
2,185 Estimating Join Selectivities using Bandwidth-Optimized Kernel Density Models 2017 VLDB 9.0583954e-05
2,244 GORDIAN: Efficient and Scalable Discovery of Composite Keys 2006 VLDB 8.9465445e-05
2,487 Active Learning for ML Enhanced Database Systems 2020 SIGMOD 8.5859375e-05
2,563 Statistical Learning Techniques for Costing XML Queries 2005 VLDB 8.4780924e-05
2,662 Fauce: Fast and Accurate Deep Ensembles with Uncertainty for Cardinality Estimation 2021 VLDB 8.344893e-05
2,780 Cost Models for Big Data Query Processing: Learning, Retrofitting, and Our Findings 2020 SIGMOD 8.1936279e-05
2,863 Scalable and Adaptive Online Joins 2014 VLDB 8.0905637e-05
2,937 Query Optimizers: Time to Rethink the Contract? 2009 SIGMOD 8.0072565e-05
2,944 Adapting to Source Properties in Processing Data Integration Queries 2004 SIGMOD 7.990048e-05
3,029 Towards a Hands-Free Query Optimizer through Deep Learning 2019 CIDR 7.8972226e-05
3,041 A Unified Deep Model of Learning from both Data and Queries for Cardinality Estimation 2021 SIGMOD 7.8821124e-05
3,108 FactorJoin: A New Cardinality Estimation Framework for Join Queries 2023 SIGMOD 7.8122622e-05
3,157 How to Fit when No One Size Fits 2013 CIDR 7.7568311e-05
3,268 Conditional Selectivity for Statistics on Query Expressions 2004 SIGMOD 7.6459051e-05
3,451 Exact Cardinality Query Optimization for Optimizer Testing 2009 VLDB 7.4749615e-05
3,475 Robust Query Driven Cardinality Estimation under Changing Workloads 2023 VLDB 7.4606119e-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 0.0024179717
35 Improved Histograms for Selectivity Estimation of Range Predicates 1996 SIGMOD 0.00048862242
98 On the Propagation of Errors in the Size of Join Results 1991 SIGMOD 0.00034732081
100 Selectivity Estimation Without the Attribute Value Independence Assumption 1997 VLDB 0.00034549997
150 Efficient Mid-Query Re-Optimization of Sub-Optimal Query Execution Plans 1998 SIGMOD 0.00029370827
221 Adaptive Selectivity Estimation Using Query Feedback 1994 SIGMOD 0.00024405057
234 Fast Incremental Maintenance of Approximate Histograms 1997 VLDB 0.00024050031
409 Cost-based Query Scrambling for Initial Delays 1998 SIGMOD 0.0001903673
438 Self-tuning Histograms: Building Histograms Without Looking at Data 1999 SIGMOD 0.00018515832
921 Selectivity Estimation and Query Optimization in Large Databases with Highly Skewed Distributions of Column Values 1988 VLDB 0.00013262691
2,945 Multiple Join Size Estimation by Virtual Domains (extended abstract) 1993 PODS 7.9899955e-05
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Semantically Similar Papers

Overall Rank Paper Year Venue Pagerank
828 Proactive Re-Optimization 2005 SIGMOD 0.00013826991
1,250 Sampling-Based Query Re-Optimization 2016 SIGMOD 0.00011563119
6,888 Lemo: A Cache-Enhanced Learned Optimizer for Concurrent Queries 2023 SIGMOD 5.8154414e-05
157 Neo: A Learned Query Optimizer 2019 VLDB 0.00028782395
6,698 Speeding Up End-to-end Query Execution via Learning-based Progressive Cardinality Estimation 2023 SIGMOD 5.8569921e-05
11,352 DeepO: A Learned Query Optimizer 2022 SIGMOD 5.1725247e-05
4,507 LEON: A New Framework for ML-Aided Query Optimization 2023 VLDB 6.723287e-05
10,225 LIO: A lightweight and interpretable query optimizer based on an evolutionary forest 2026 VLDB 5.1725247e-05
2,506 Lero: A Learning-to-Rank Query Optimizer 2023 VLDB 8.5603022e-05
7,996 Learning Table Access Cardinalities with LEO 2002 SIGMOD 5.5674596e-05