For a vector search to be useful, it needs to be fast and accurate. Approximate similarity searches seek a balance between these goals.

• Understand Approximate Similarity Search Using Vector Indexes
  For faster search speeds with large vector spaces, you can use approximate similarity search using vector indexes.
• Optimizer Plans for Vector Indexes
  Optimizer plans for HNSW and IVF indexes are described in the following sections.
• Approximate Similarity Search Examples
  Review these examples to see how you can perform an approximate similarity search using vector indexes.