Results for SimilaritySearch in RAG Application with Ollama always return 0 documents

[cjullien]

Bug description
When I create a RAG Application with SimilaritySearch, the search returns similar documents when using Azure OpenAI, but always returns zero documents with Ollama. The issue occurs specifically when I use the withSimilarityThreshold parameter with Ollama.

Environment
last version of spring-ai BOM
ollama with llama 3.2
Azure OpenAI
PGVector

Steps to reproduce
When I use withSimilarityThreshold with Ollama, I always have 0 Document in my similarDocuments (it's ok with Azure OpenAI)

   var similarity = 0.8; 
    var topk =20;
    var searchRequest = SearchRequest.query(question.question())
            .withTopK(topk)
            .withSimilarityThreshold(similarity);
     List<Document> similarDocuments = vectorStore.similaritySearch(searchRequest);

Expected behavior
The search should return similar results between Azure OpenAI and Ollama. However, Ollama consistently returns zero similar documents.

Observed Behavior

Azure OpenAI: Returns a list of documents that meet the similarity threshold.
Ollama: Returns zero documents, regardless of the similarity threshold set.

Additional Information

Configuration Consistency: The vectorStore configuration is identical for both platforms.
Error Logs: No explicit error messages are thrown; however, the empty response from Ollama does not align with the expected output.
[spring-ai-bootstraping] [nio-8080-exec-1] c.c.s.s.controller.AskRagController : Found 0 similar documents

[asaikali]

What embedding model are you using with ollama?

[cjullien]

I tested with the following models

#spring.ai.ollama.embedding.options.model=nomic-embed-text
#spring.ai.ollama.embedding.options.model=mxbai-embed-large
spring.ai.ollama.embedding.options.model=chroma/all-minilm-l6-v2-f32
#spring.ai.ollama.embedding.options.model=hellord/e5-mistral-7b-instruct:Q4_0