Add Inspeximus document store integration

[DanceNitra]

Adds a Document Store integration page for Inspeximus (MIT, on PyPI as inspeximus).

InspeximusDocumentStore implements Haystack's DocumentStore protocol as a drop-in for InMemoryDocumentStore, with two differences that matter for long-running or regulated pipelines: it persists to a file, and its delete_documents removes the value from disk (with receipts enabled, leaving a signed, content-free tombstone so a deletion is provable).

It is a faithful drop-in — the duplicate policies (SKIP, OVERWRITE, NONE, FAIL) match InMemoryDocumentStore exactly (captured from the reference, not guessed), and filtering reuses Haystack's own document_matches_filter, so FilterRetriever and pipeline serialization work unchanged. Parity is verified in CI against InMemoryDocumentStore, operation by operation, with a falsification control that must fail.

The usage example in the page was run end to end against haystack-ai 3.0.0 and inspeximus 1.29.0, and produces the output shown.

No logo included for now; happy to add one if you'd like it before merge.

This page was drafted with AI assistance; a human reviewed it and ran the example.

[vercel]

Someone is attempting to deploy a commit to the deepset Team on Vercel.

A member of the Team first needs to authorize it.

[Copilot]

Pull request overview

• Adds a new integration documentation page for the inspeximus Python package, describing InspeximusDocumentStore as a persistent, file-backed Haystack DocumentStore with provable deletion semantics.

Changes:

• Adds integrations/inspeximus.md with overview, install instructions, and end-to-end usage snippets.
• Documents persistence + receipted erasure behavior and positions it as a drop-in alternative to InMemoryDocumentStore.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[kacperlukawski]

Thank you, @DanceNitra Could you please help me understand if the integration comes from an actual need of any user? I would like to know if that's going to be helpful for broader audience.

[DanceNitra]

Honest answer: no, this didn't come from a user request. I built the adapter because inspeximus ships a document store and Haystack was a natural target, and I wanted the "drop-in" claim to be tested rather than asserted — so it runs against your own InMemoryDocumentStore in CI, with a control that deliberately breaks ours and requires the comparison to fail.

But that's an answer about correctness, not about demand, and demand is what you asked about. I don't have a user to point to. If your bar for the integrations catalogue is demonstrated need, this doesn't clear it, and I'd rather you close or park it than have it sit there implying an adoption that doesn't exist.

For what it's worth on the "broader audience" question: the thing inspeximus does differently from an in-memory store is deletion — delete_documents removes the value from disk, not just from the index — plus provenance on writes. That matters to people with a retention or erasure obligation and is irrelevant to everyone else, so it's a narrow audience by design.

Happy either way. Thanks for looking at it.