# Pinecone not returning documents after successful upload - FastAPI + LangChain integration

**URL:** <https://community.pinecone.io/t/pinecone-not-returning-documents-after-successful-upload-fastapi-langchain-integration/8410>\
**Category:** Support\
**Created:** [October 7, 2025, 3:17pm UTC](https://community.pinecone.io/t/pinecone-not-returning-documents-after-successful-upload-fastapi-langchain-integration/8410 "2025-10-07T15:17:30Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![jony](https://sea2.discourse-cdn.com/flex020/user_avatar/community.pinecone.io/jony/32/3151_2.png) [@jony](https://community.pinecone.io/u/jony)\
**Post date:** [October 7, 2025, 3:17pm UTC](https://community.pinecone.io/t/pinecone-not-returning-documents-after-successful-upload-fastapi-langchain-integration/8410/1 "2025-10-07T15:17:30Z")

</div>

Hello Pinecone Community,

We’re facing a critical issue with our production system, and would appreciate your insight.

**System Context:**

- **Backend:** FastAPI (Python 3.11)

- **Vector DB:** Pinecone (serverless, free and considering upgrade to Standard)

- **ORM:** SQLAlchemy with PostgreSQL (hosted on Railway)

- **Framework:** LangChain

- **LLM/Embeddings:** OpenAI GPT-4o-mini, text-embedding-ada-002

**How it works:**

- Users upload PDF/TXT files via FastAPI endpoint.

- Text is extracted (PyPDF2/pdfplumber), split into chunks (RecursiveCharacterTextSplitter).

- Chunks are embedded and upserted to Pinecone under namespace format: **`user_{user_id}_cond_{condo_id}`**.

- Each condominium and user has an isolated namespace; there is strict separation by design.

- Queries are routed to Pinecone via LangChain with the respective namespace.

**Symptoms:**

- Upload endpoint reports success (no errors shown).

- Chunks are successfully processed and upserted to Pinecone (confirmed by logs).

- When querying, LangChain searches the correct namespace (confirmed by logs).

- Query always returns empty/None, or otherwise “No documents found,” even immediately after upload.

**What we’ve checked:**

- Document model strictly matches DB schema (no extraneous or missing fields).

- Upload process and query both use the same embedding model and chunking parameters.

- Namespace string is identical between upsert and query.

- Pinecone’s **`describe_index_stats()`** shows the namespace being created, but sometimes the vector count is inconsistent or remains zero after upload.

- PostgreSQL database does not report any constraint violations.

**What we’ve tried:**

- Re-uploaded files with minimal and default metadata.

- Completely cleared and recreated Pinecone namespaces and indexes.

- Stripped any special characters from namespace names and file names.

- Debugged LangChain pipeline with smaller texts and synthetic documents: still no results.

**Questions:**

- What are the most common causes for successfully upserted vectors being “invisible” to queries (especially in serverless/Starter tier)?

- Are there edge cases in metadata, namespace, or embedding config that would cause vectors to not be returned or to be dropped silently?

- Could there be issues with chunking length, batch size, or API rate limits where the upsert reports no error but nothing is persisted?

- Is there a restricted feature set on Starter tier that could block retrieval in isolation scenarios?

- Any recommended debugging steps with Pinecone CLI/API to confirm vectors, or to test “raw” queries bypassing LangChain?

We are ready to provide code samples/logs and can migrate to Standard plan if that helps unlock advanced diagnostics/support.

**Thank you for any help,**  
Team AlexandraLex