What happens when querying with an IVF index if you increase the value of the NEIGHBOR_PARTITIONS probes parameter?

The NEIGHBOR_PARTITIONS parameter in Oracle 23ai’s IVF index controls how many partitions are probed during a query. Increasing this value examines more clusters, raising theprobability of finding relevant vectors, thus improving accuracy (recall). However, this increases computational effort, leading to higher query latency—a classic ANN trade-off. The number of centroids (A) is fixed during index creation and unaffected by query parameters. Accuracy does not decrease (B); it improves. Index creation time (C) is unrelated to query-time settings. Oracle’s documentation on IVF confirms that NEIGHBOR_PARTITIONS directly governs this accuracy-latency balance.
Reference:Oracle Database 23ai AI Vector Search Guide, Section on IVF Query Parameters.