Why Are Learned Indexes So Effective but Sometimes Ineffective?

Summary: The paper gives a theoretical account of PGM-Index effectiveness and pins practical slowdown to memory-bound queries and expensive internal search. Introduces PGM++—a mix-of-search-strategies with cost-model auto-tuning—achieving much faster lookups at similar space. (summarized by gpt-5-mini on Feb 09 2026)

Paper ID: 13928
Venue: VLDB
Year: 2025
Pagerank: 4.2897489e-05
Overall Rank: 9,746 | 32.20%
DOI: 10.14778/3746405.3746415

Incoming Non-self Citations Over Time

Authors

Incoming Citations (Sorted by Pagerank)

Showing 2 of 2 citing papers.

Rank	Citing Paper	Year	Venue	Pagerank
10,172	HIRE: A Hybrid Learned Index for Robust and Efficient Performance under Mixed Workloads	2026	SIGMOD	4.1945683e-05
10,698	Not Small Enough? SegPQ: A Learned Approach to Compress Product Quantization Codebooks	2025	VLDB	4.1945683e-05

Outgoing Citations (Sorted by Pagerank)

Showing 20 of 20 cited papers.

Citations counted here include only citations to other VLDB/SIGMOD/CIDR/PODS papers in this database.

Rank	Cited Paper	Year	Venue	Pagerank
102	The Case for Learned Index Structures	2018	SIGMOD	0.00049545203
381	FAST: Fast Architecture Sensitive Tree Search on Modern CPUs and GPUs	2010	SIGMOD	0.00024873637
826	ALEX: An Updatable Adaptive Learned Index	2020	SIGMOD	0.00016224841
857	The PGM-index: a fully-dynamic compressed learned index with provable worst-case bounds	2020	VLDB	0.00015882892
1,087	HOT: A Height Optimized Trie Index for Main-Memory Database Systems	2018	SIGMOD	0.00014162909
1,375	FITing-Tree: A Data-aware Index Structure	2019	SIGMOD	0.00012303141
1,460	Benchmarking Learned Indexes	2021	VLDB	0.00011887068
2,552	Updatable Learned Index with Precise Positions	2021	VLDB	8.5530411e-05
2,732	Efficiently Searching In-Memory Sorted Arrays: Revenge of the Interpolation Search?	2019	SIGMOD	8.2087602e-05
4,060	CDFShop: Exploring and Optimizing Learned Index Structures	2020	SIGMOD	6.4836825e-05
4,128	Are Updatable Learned Indexes Ready?	2022	VLDB	6.4292373e-05
4,446	Stable Learned Bloom Filters for Data Streams	2020	VLDB	6.1800659e-05
4,646	CARMI: A Cache-Aware Learned Index with a Cost-based Construction Algorithm	2022	VLDB	6.0250374e-05
5,074	Learned Index: A Comprehensive Experimental Evaluation	2023	VLDB	5.7175726e-05
5,319	DILI: A Distribution-Driven Learned Index	2023	VLDB	5.5713974e-05
5,592	PLIN: A Persistent Learned Index for Non-Volatile Memory with High Performance and Instant Recovery	2023	VLDB	5.4210633e-05
5,642	NFL: Robust Learned Index via Distribution Transformation	2022	VLDB	5.3929294e-05
6,461	An Eight-Dimensional Systematic Evaluation of Optimized Search Algorithms on Modern Processors	2018	VLDB	5.0538774e-05
7,390	Making In-Memory Learned Indexes Efficient on Disk	2024	SIGMOD	4.7431654e-05
8,650	HAP: An Efficient Hamming Space Index Based on Augmented Pigeonhole Principle	2022	SIGMOD	4.4761716e-05

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Overall Rank	Paper	Year	Venue	Pagerank
9,346	Can Learned Indexes be Built Efficiently? A Deep Dive into Sampling Trade-offs	2024	SIGMOD	4.3532026e-05
2,552	Updatable Learned Index with Precise Positions	2021	VLDB	8.5530411e-05
5,157	Hist-Tree: Those Who Ignore It Are Doomed to Learn	2021	CIDR	5.6589595e-05
8,811	Tuning Hierarchical Learned Indexes on Disk and Beyond	2022	SIGMOD	4.4441574e-05
102	The Case for Learned Index Structures	2018	SIGMOD	0.00049545203
7,390	Making In-Memory Learned Indexes Efficient on Disk	2024	SIGMOD	4.7431654e-05
1,460	Benchmarking Learned Indexes	2021	VLDB	0.00011887068
5,074	Learned Index: A Comprehensive Experimental Evaluation	2023	VLDB	5.7175726e-05
6,445	Updatable Learned Indexes Meet Disk-Resident DBMS - From Evaluations to Design Choices	2023	SIGMOD	5.0589805e-05
857	The PGM-index: a fully-dynamic compressed learned index with provable worst-case bounds	2020	VLDB	0.00015882892