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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
8726
Venue
VLDB
Year
2001
Pagerank
0.00036962631
Overall Rank
182 | 98.74%
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
71 How Good Are Query Optimizers, Really? 2016 VLDB 0.00059038975
224 CORDS: Automatic Discovery of Correlations and Soft Functional Dependencies 2004 SIGMOD 0.00032746205
325 The History of Histograms (abridged) 2003 VLDB 0.00027378328
333 Neo: A Learned Query Optimizer 2019 VLDB 0.00027206884
640 Bao: Making Learned Query Optimization Practical 2021 SIGMOD 0.00018759152
650 Robust Query Processing through Progressive Optimization 2004 SIGMOD 0.00018659177
758 Deep Unsupervised Cardinality Estimation 2020 VLDB 0.0001706608
790 Exploiting Statistics on Query Expressions for Optimization 2002 SIGMOD 0.0001663283
846 Self-tuning Database Technology and Information Services: from Wishful Thinking to Viable Engineering 2002 VLDB 0.00015997985
884 Plan-Structured Deep Neural Network Models for Query Performance Prediction 2019 VLDB 0.00015654004
910 NeuroCard: One Cardinality Estimator for All Tables 2021 VLDB 0.00015423056
1,019 Robust Estimation of Resource Consumption for SQL Queries using Statistical Techniques 2012 VLDB 0.00014625603
1,043 Adaptive Ordering of Pipelined Stream Filters 2004 SIGMOD 0.00014476247
1,070 Analyzing Plan Diagrams of Database Query Optimizers 2005 VLDB 0.00014316791
1,105 Cardinality Estimation Done Right: Index-Based Join Sampling 2017 CIDR 0.00013990395
1,228 Toward a Progress Indicator for Database Queries 2004 SIGMOD 0.00013164884
1,254 Selectivity Estimation for Range Predicates using Lightweight Models 2019 VLDB 0.00013027411
1,300 The Picasso Database Query Optimizer Visualizer 2010 VLDB 0.00012733214
1,443 Compressing SQL Workloads 2002 SIGMOD 0.00011947004
1,512 Estimating Progress of Execution for SQL Queries 2004 SIGMOD 0.00011597041
1,638 Cardinality Estimation in DBMS: A Comprehensive Benchmark Evaluation 2022 VLDB 0.00011049779
1,737 QuickSel: Quick Selectivity Learning with Mixture Models 2020 SIGMOD 0.00010720294
1,758 Sampling-Based Query Re-Optimization 2016 SIGMOD 0.00010655546
1,855 AI Meets AI: Leveraging Query Executions to Improve Index Recommendations 2019 SIGMOD 0.00010315245
1,974 BHUNT: Automatic Discovery of Fuzzy Algebraic Constraints in Relational Data 2003 VLDB 9.8866171e-05
2,083 Towards a Learning Optimizer for Shared Clouds 2019 VLDB 9.5834572e-05
2,137 SASH: A Self-Adaptive Histogram Set for Dynamically Changing Workloads 2003 VLDB 9.4719326e-05
2,156 SkinnerDB: Regret-Bounded Query Evaluation via Reinforcement Learning 2018 VLDB 9.4170209e-05
2,219 SkinnerDB: Regret-Bounded Query Evaluation via Reinforcement Learning 2019 SIGMOD 9.2623533e-05
2,356 Consistently Estimating the Selectivity of Conjuncts of Predicates 2005 VLDB 8.9620762e-05
2,549 GORDIAN: Efficient and Scalable Discovery of Composite Keys 2006 VLDB 8.5641554e-05
2,596 WeTune: Automatic Discovery and Verification of Query Rewrite Rules 2022 SIGMOD 8.4729982e-05
2,631 Plan Bouquets: Query Processing without Selectivity Estimation 2014 SIGMOD 8.4101843e-05
2,665 Statistical Learning Techniques for Costing XML Queries 2005 VLDB 8.3498101e-05
2,669 A Black-Box Approach to Query Cardinality Estimation 2007 CIDR 8.3389856e-05
2,762 FLAT: Fast, Lightweight and Accurate Method for Cardinality Estimation 2021 VLDB 8.1585394e-05
2,969 Estimating Join Selectivities using Bandwidth-Optimized Kernel Density Models 2017 VLDB 7.7974762e-05
3,034 How to Fit when No One Size Fits 2013 CIDR 7.6752083e-05
3,142 Active Learning for ML Enhanced Database Systems 2020 SIGMOD 7.4815444e-05
3,330 Adapting to Source Properties in Processing Data Integration Queries 2004 SIGMOD 7.2150831e-05
3,382 Scalable and Adaptive Online Joins 2014 VLDB 7.1597145e-05
3,408 Query Optimizers: Time to Rethink the Contract? 2009 SIGMOD 7.1288167e-05
3,499 Fauce: Fast and Accurate Deep Ensembles with Uncertainty for Cardinality Estimation 2021 VLDB 7.0376445e-05
3,625 Cost Models for Big Data Query Processing: Learning, Retrofitting, and Our Findings 2020 SIGMOD 6.9055212e-05
3,651 Conditional Selectivity for Statistics on Query Expressions 2004 SIGMOD 6.8768678e-05
3,658 Towards a Hands-Free Query Optimizer through Deep Learning 2019 CIDR 6.8704209e-05
3,717 Lazy, Adaptive RID-List Intersection, and Its Application to Index Anding 2007 SIGMOD 6.8210203e-05
3,924 A Unified Deep Model of Learning from both Data and Queries for Cardinality Estimation 2021 SIGMOD 6.6271553e-05
3,952 Exact Cardinality Query Optimization for Optimizer Testing 2009 VLDB 6.5939652e-05
3,973 Apache Hive: From MapReduce to Enterprise-grade Big Data Warehousing 2019 SIGMOD 6.5758017e-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 0.0040449103
64 Improved Histograms for Selectivity Estimation of Range Predicates 1996 SIGMOD 0.00063612837
99 On the Propagation of Errors in the Size of Join Results 1991 SIGMOD 0.00050022914
141 Selectivity Estimation Without the Attribute Value Independence Assumption 1997 VLDB 0.00041786333
220 Efficient Mid-Query Re-Optimization of Sub-Optimal Query Execution Plans 1998 SIGMOD 0.00033194808
252 Adaptive Selectivity Estimation Using Query Feedback 1994 SIGMOD 0.00030632263
269 Fast Incremental Maintenance of Approximate Histograms 1997 VLDB 0.00029656549
456 Cost-based Query Scrambling for Initial Delays 1998 SIGMOD 0.00022717134
529 Self-tuning Histograms: Building Histograms Without Looking at Data 1999 SIGMOD 0.00020828852
897 Selectivity Estimation and Query Optimization in Large Databases with Highly Skewed Distributions of Column Values 1988 VLDB 0.00015528028
3,053 Multiple Join Size Estimation by Virtual Domains (extended abstract) 1993 PODS 7.64969e-05
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Semantically Similar Papers

Overall Rank Paper Year Venue Pagerank
1,272 Proactive Re-Optimization 2005 SIGMOD 0.00012920076
1,758 Sampling-Based Query Re-Optimization 2016 SIGMOD 0.00010655546
7,330 Lemo: A Cache-Enhanced Learned Optimizer for Concurrent Queries 2023 SIGMOD 4.7609373e-05
333 Neo: A Learned Query Optimizer 2019 VLDB 0.00027206884
7,221 Speeding Up End-to-end Query Execution via Learning-based Progressive Cardinality Estimation 2023 SIGMOD 4.797194e-05
11,350 DeepO: A Learned Query Optimizer 2022 SIGMOD 4.1945683e-05
5,334 LEON: A New Framework for ML-Aided Query Optimization 2023 VLDB 5.5649836e-05
10,225 LIO: A lightweight and interpretable query optimizer based on an evolutionary forest 2026 VLDB 4.1945683e-05
3,348 Lero: A Learning-to-Rank Query Optimizer 2023 VLDB 7.1904529e-05
8,113 Learning Table Access Cardinalities with LEO 2002 SIGMOD 4.5826944e-05