A RediSearch vector index that compares every vector exactly, by brute force. It fits smaller data sets or cases needing complete results, whereas HNSW is approximate.
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In the Ultra Transcenders books
Each book explains FLAT in context, with comparison tables and the common traps.
Terms in this definition
- RediSearch
A Redis module for Azure Managed Redis that provides secondary indexes plus full-text and vector search. It can only be turned on when the cache is created and needs Enterprise clustering with the NoEviction policy.
- Vector index
An entry in a Cosmos DB indexing policy, of type flat, quantizedFlat or diskANN, that makes VectorDistance searches faster. It can't be changed once created and needs the vector search feature turned on.
- Deployment modes
The two ways ARM can deploy: Incremental, the default, creates or updates what the template lists and ignores everything else; Complete also removes resource group contents absent from the template.
- HNSW
Graph-structured index for approximate vector search in RediSearch and pgvector. Compared with IVFFlat, recall versus speed is better, though building takes longer and memory use is higher.
Related terms
- ANN
Short for approximate nearest neighbour: a vector search that finds most of the closest matches rather than guaranteeing every one, trading completeness for speed and lower cost. DiskANN and HNSW indexes work this way, whereas flat search is exact.
- CSV
Plain-text format with comma-separated values, often used for flat exports such as an HR file feeding API-driven provisioning.