retriever for vector store search #10994

mubashir1osmani · 2026-01-17T03:15:57Z

mubashir1osmani
Jan 17, 2026

hi, just wondering how retriever span kind works in phoenix, im using a vector store to fetch from sources which i can see in my metadata but the retriever span is completely empty

isnt it supposed to show me sources used from the vector store?

@mubashir1osmani · 2026-01-17T03:20:37Z

dosubot[bot]
bot Jan 17, 2026

Hi @mubashir1osmani! I'm Dosu and I’m helping the phoenix team.

Yes, retriever spans in Phoenix are supposed to show the sources (documents) fetched from your vector store, including their metadata and content. If your retriever span is empty, it usually means the span isn't being properly instrumented or the attributes for the retrieved documents aren't being set as expected.

Phoenix expects retriever spans to have attributes like retrieval.documents.0.document.content, retrieval.documents.0.document.id, and retrieval.documents.0.document.metadata for each document retrieved. These attributes are either set automatically if you're using frameworks like LangChain or LlamaIndex with auto-instrumentation, or you need to set them manually if you're using a custom retriever or vector store integration. If these attributes are missing or empty, the retriever span will appear empty in the UI—even if you see sources elsewhere in your metadata.

For manual instrumentation, you should wrap your vector store search in a span like this:

with tracer.start_as_current_span("vector_store_search", openinference_span_kind="RETRIEVER") as span:
    docs = vector_store.search(query, limit=5)
    for i, doc in enumerate(docs):
        span.set_attribute(f"retrieval.documents.{i}.document.id", doc.id)
        span.set_attribute(f"retrieval.documents.{i}.document.content", doc.content)
        span.set_attribute(f"retrieval.documents.{i}.document.metadata", json.dumps(doc.metadata))

If you're using LangChain or LlamaIndex and still seeing empty retriever spans, check that you're on a compatible version (there are known issues with some recent versions, e.g., llama_index-core 0.13.0+), and that your tracing is properly registered and enabled for those frameworks [source].

If you see sources in your metadata but not in the retriever span, double-check that your retriever span is actually being created and that the attributes are being set as described above. Also, make sure your export configuration isn't dropping spans before they reach Phoenix [source].

Let me know if you want help with a specific code snippet or setup!

To reply, just mention @dosu.

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