AlloyDB now provides more accurate memory usage estimation, and it prevents out-of-memory (OOM) errors when you build a ScaNN four-level tree index

## Fix Fixed AlloyDB now provides more accurate memory usage estimation, and it prevents out-of-memory (OOM) errors when you build a ScaNN [four-level tree index](https://cloud.google.com/alloydb/docs/ai/create-scann-index#create-scann-index-manual). This feature is in [Preview](https://cloud.google.com/products#product-launch-stages). This update improves the stability of index builds by enforcing memory limits and improving memory estimation under constrained conditions. For more information, see [Create a ScaNN index](https://cloud.google.com/alloydb/docs/ai/create-scann-index#create-scann-index-manual).