CubeGraph: Efficient Retrieval-Augmented Generation for Spatial and Temporal Data

TL;DR

CubeGraph introduces a unified indexing framework that efficiently combines vector similarity search with spatial constraints, improving performance and scalability for hybrid spatial-temporal queries in retrieval-augmented systems.

Contribution

It proposes a novel hierarchical grid-based index that dynamically stitches vector graphs across spatial cells, restoring connectivity and enabling single-pass nearest-neighbor traversal.

Findings

CubeGraph outperforms existing methods in real-world dataset benchmarks.

It achieves higher query efficiency and scalability for complex hybrid workloads.

The framework effectively integrates spatial and vector data without fragmentation.

Abstract

Hybrid queries combining high-dimensional vector similarity search with spatio-temporal filters are increasingly critical for modern retrieval-augmented generation (RAG) systems. Existing systems typically handle these workloads by nesting vector indices within low-dimensional spatial structures, such as R-trees. However, this decoupled architecture fragments the vector space, forcing the query engine to invoke multiple disjoint sub-indices per query. This fragmentation destroys graph routing connectivity, incurs severe traversal overhead, and struggles to optimize for complex spatial boundaries. In this paper, we propose CubeGraph, a novel indexing framework designed to natively integrate vector search with arbitrary spatial constraints. CubeGraph partitions the spatial domain using a hierarchical grid, maintaining modular vector graphs within each cell. During query execution, CubeGraph dynamically stitches together adjacent cube-level indices on the fly whenever their spatial cells intersect with the query filter. This dynamic graph integration restores global connectivity, enabling a unified, single-pass nearest-neighbor traversal that eliminates the overhead of fragmented sub-index invocations. Extensive evaluations on real-world datasets demonstrate that CubeGraph significantly outperforms state-of-the-art baselines, offering superior query execution performance, scalability, and flexibility for complex hybrid workloads.