# `gno.land/r/moul/x/compact/v0` Fragmentation, as a number you can act on. A soft delete frees nothing. It clears the element and leaves the tree node behind, so the bytes stay locked and every read still walks past the hole. Compacting drops those nodes, and the chain refunds their deposit **to whoever signs the transaction**. Compaction is therefore paid work, and the only real question is *when*: too early and you free too few nodes to cover the gas, too late and every read has been paying for the holes in between. This realm refuses to answer that question. It publishes the integers the answer is made of and lets whoever is watching decide, because the realm cannot see the gas price of the day and the caller can. ## The interface | | | |---|---| | `Add(text)` | appends an entry and locks its deposit against you | | `Drop(index)` | soft-deletes **your own** entry, which is what creates a hole. Frees nothing | | `Compact()` | drops the dead nodes. Permissionless, and the refund goes to you | | `Fragmentation()` | live against allocated, the free read a bot polls | | `Reclaimable()` | what a `Compact` would actually free right now | | `Quote()` | that, priced, as a `storagecost.Quote` | Only the author may `Drop`, so the fragmentation here is the honest kind that ordinary use produces rather than vandalism. `Compact` stays open to anyone, and that asymmetry is the mechanism: **choosing what dies is owned, reclaiming it is not.** ## Why `allocated - live` is the wrong number The obvious reading of fragmentation is the gap between allocated indices and live elements. It is not what a compaction frees. A dead element only becomes a reclaimable node once **everything under it is also dead**. So a board with many scattered holes reports a large gap and reclaims almost nothing, while a board with a dead tail reclaims a lot from the same gap. `Reclaimable()` is the real number and it is free to read. That is the whole reason this cannot be a schedule or a heuristic baked into the package. The shape of the holes decides, the shape changes with use, and only a caller watching both integers can time it. ## Why this quote is sounder than a reaper's A reaper advertises what deleting entries will refund, and to do that it has to guess how much state an entry occupies from its payload length. That guess is bad at the small end, where a per-entry floor dominates the payload, and one realm under-advertised by **25x** on chain because of it. Compaction has no such problem: | | reaper's bounty | this quote | |---|---|---| | quantity | payload bytes, **guessed** from string length | dead nodes, **counted** by the container | | conversion | a ratio measured at one payload size | a per-node constant, measured twice at 856 bytes | | fails when | entries are small, or the container dominates | never structurally; the constant can drift | `Quote()` is a measured constant times an exact integer. Still an estimate, and the chain's `StorageUnlockEvent` is still the only settlement, but the failure mode that cost a reaper 25x is absent by construction. `TestQuoteCountsNodesRatherThanGuessingFromPayload` pins it: eight entries of 1 byte and eight of 256 produce the identical quote, because the node is what gets freed. ## What it is built from - [`p/moul/ulist`](https://github.com/moul/gno-contracts/tree/main/p/moul/ulist) stores the entries and owns compaction. Its `Compact` drops dead nodes without moving a live index, so an index is stable for the life of the realm. - [`p/moul/x/storagecost`](https://github.com/moul/gno-contracts/tree/main/p/moul/x/storagecost) owns the arithmetic, including `EstimateNodes` and the measured `BytesPerTreeNode`. - [`p/moul/kit/ui`](https://github.com/moul/gno-contracts/tree/main/p/moul/kit/ui) owns the display, including escaping an entry before it reaches the page. ## Related [`r/moul/x/reaper`](https://github.com/moul/gno-contracts/tree/main/r/moul/x/reaper) is the other half: it deletes expired entries, where this one reclaims what deletion left behind. Reap first, then compact, because compaction returns nothing while a live element still sits below the dead ones. --- Part of **[moul/gno-contracts](https://github.com/moul/gno-contracts)** โ€” moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage. **Dependency graph:** ![gno.land/r/moul/x/compact/v0 dependency graph](https://raw.githubusercontent.com/moul/gno-contracts/main/_assets/gno.land/r/moul/x/compact/v0/deps.png) > ๐Ÿงช **Highly experimental โ€” potentially vibe-coded.** Not audited; may break, change, or be removed at any time. Do not use with anything of value. Full disclaimer: [DISCLAIMER](https://github.com/moul/gno-contracts/blob/main/DISCLAIMER.md).