What is the SearchRequest API in Spring AI's VectorStore?

SearchRequest is the query object you pass to VectorStore.similaritySearch(). It encapsulates the query string plus optional filters — maximum results, similarity threshold, and metadata filter expressions — so you can constrain what documents come back rather than retrieving everything above some similarity floor.

// Basic: top-5 most similar documents
List<Document> docs = vectorStore.similaritySearch(
    SearchRequest.query(userQuestion).withTopK(5));

// With similarity threshold — only return docs scoring above 0.75
List<Document> precise = vectorStore.similaritySearch(
    SearchRequest.query(userQuestion)
        .withTopK(5)
        .withSimilarityThreshold(0.75));

// With metadata filter — only search documents from a specific source
Filter.Expression filter = new Filter.ExpressionBuilder()
    .eq("source", "spring-ai-docs.pdf")
    .build();
List<Document> filtered = vectorStore.similaritySearch(
    SearchRequest.query(userQuestion)
        .withTopK(5)
        .withFilterExpression(filter));

The metadata filter uses an expression builder API that is translated by each VectorStore implementation into its native query language — SQL WHERE clause for PgVector, Redis filter syntax for Redis, Pinecone metadata filter JSON, etc. This means your filter logic is portable and does not leak provider-specific syntax into application code.

Tuning topK and similarityThreshold is a key RAG quality lever. Returning too many low-relevance documents bloats the prompt and can confuse the model; returning too few may miss critical context.

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