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A data engineering team is implementing a Retrieval-Augmented Generation (RAG) system on Google Cloud. They use Vertex AI text embedding models to generate high-dimensional vector embeddings of unstructured technical articles and index them using Vertex AI Vector Search with the Tree-AH algorithm.
During evaluation, the team discovers that while query response latency is extremely low, the index's Approximate Nearest Neighbor (ANN) search recall is insufficient, causing relevant context to be missed during generative AI grounding.
Which configuration change should the team make to improve search recall?
Switch the index update method from Stream update to Batch update
Decrease the leaf_nodes_to_search_percent parameter in the Tree-AH algorithm configuration
Increase the leaf_nodes_to_search_percent parameter in the Tree-AH algorithm configuration
Deploy the index to an endpoint configured with a higher minReplicaCount and autoscaling enabled
Switch the index update method from Stream update to Batch update
Decrease the leaf_nodes_to_search_percent parameter in the Tree-AH algorithm configuration
Increase the leaf_nodes_to_search_percent parameter in the Tree-AH algorithm configuration
Vertex AI Vector Search utilizes the Tree-AH (Tree Asymmetric Hashing) algorithm based on Google's ScaNN library to provide high-speed, scalable Approximate Nearest Neighbor (ANN) search. The leaf_nodes_to_search_percent parameter specifies the percentage of index leaf nodes evaluated during a nearest neighbor query.
leaf_nodes_to_search_percent instructs the search engine to traverse and scan a larger proportion of candidate leaf nodes, directly expanding the candidate search pool.Adjusting leaf_nodes_to_search_percent directly targets the trade-off between recall and latency in Tree-AH indexes. It provides the necessary retrieval precision for generative AI pipelines while retaining the scalability benefits of approximate nearest neighbor indexing.
Deploy the index to an endpoint configured with a higher minReplicaCount and autoscaling enabled