Glossary
What is Index pruning?
Verified 21 September 2026
A bounded index must remove things to admit new ones. The question is what, and on what evidence: near-duplicates, superseded versions, content past its useful life, passages nothing has retrieved in a long time, or weaker members of a saturated semantic cell.
Pruning is where indexes quietly get worse. Removing the last carrier of a rare term destroys exact-match recall for that term permanently, and nothing in the semantic space substitutes for it — which is why that specific removal is prohibited here.
unlob records every removal in an append-only ledger with a typed reason, queryable through why_not.
How unlob handles this: Coverage transparency
Common questions
What is Index pruning?
Pruning removes documents from an index to reclaim space, based on redundancy, staleness, access patterns or competitive replacement.
How does Index pruning work in practice?
Pruning is where indexes quietly get worse. Removing the last carrier of a rare term destroys exact-match recall for that term permanently, and nothing in the semantic space substitutes for it — which is why that specific removal is prohibited here.
See it working
The free tier is 10,000 credits a month with no card — enough to test any of this against your own queries.