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Changelog Entry

Description

Fixes: #18119
Fixes: #16345
Fixes: #17088
Fixes: #18485

Changed

• When adding files to a knowledgebase, the check for duplicates is bypassed and allows duplicate uploads

I have tried analyzing the relevant parts of the retrieval.py and knowledge.py but could not identify the actual issue.
This is because the current check for duplicates is broken for two reasons:

• When adding totally different files THAT YOU HAVE NEVER ADDED before you CAN still get the duplication error
• Vectors are never deleted from the database, making any duplication checks or hash checks solely based on the content and stored FTS content of the files obsolete

This PR was tested locally with chromadb.sqlite and a locally sqlite MILVUS database and was verified working versus without the fix.

• [Attach any relevant screenshots or videos demonstrating the changes]

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