FAISSDocumentStore issue when running Tutorial 6 and Tutorial 7 in the same Colab

[adieyal]

Describe the bug
Following the tutorial 6 and tutorial 7 in sequence on the same Colab runtime results in a FAISSDocumentStore error due to the presence of the already-created faiss_document_store.db

Related to this issue deepset-ai/haystack#1903

Error message
FAISSDocumentStore: number of documents present in the SQL database does not match the number of embeddings in FAISS

Expected behavior
Either a note in the notebook to mention that this might be expected behaviour and/or additional if...else.. code that automatically handles this.

Additional context
None

To Reproduce
Run Tutorial 6, then copy the relevant bits of code from Tutorial 7 into the same Colab.

FAQ Check

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**System: Google Colab

• OS:
• GPU/CPU: VT-100
• Haystack version (commit or version number): 1.6.1rc0
• DocumentStore: FAISSDocumentStore
• Reader:
• Retriever:

[jasontian6666]

Do I need to remove the faiss_document_store.db every time I want to index a new set of documents? If so, how can I maintain different faiss_document_store.db for different sets of documents, so I can reuse them later?