opensearch-project/OpenSearch

[Enhancement] Histogram aggregation should initialize Ranges lazily

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#18,241 opened on May 8, 2025

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 (13 comments) (0 reactions) (1 assignee)Java (8,123 stars) (1,505 forks)batch import
Search:Aggregationsenhancementgood first issue

Description

Is your feature request related to a problem? Please describe

Currently, optimized histogram aggregation using multi range traversal initialized Ranges with all buckets eagerly. While for individual request, memory implications are small, it can starting adding up across all requests on a node.

Describe the solution you'd like

Given we process buckets one at a time, they can be initialized lazily avoiding unnecessary memory allocations. This should also allow to raise the number of buckets limit from 3k to 10k or more

Related component

No response

Describe alternatives you've considered

No response

Additional context

No response

Contributor guide

Tech stack
java
Domain
backendperformancesearch
Issue type
performance
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
blocked
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaOpenSearch aggregation internalslazy initializationmemory management
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
The issue proposes lazy initialization of the Ranges object in histogram aggregation to reduce memory allocations. The implementation is likely in the aggregation module of OpenSearch, specifically in classes related to histogram aggregation. Review the current code where Ranges are eagerly created for all buckets and modify it to create Ranges only when needed, following the multi range traversal pattern described. Check issue comments for any specific file references or maintainer guidance on the preferred approach.