# `gno.land/p/moul/collection/v0`

A generic collection with multiple indexes (unique, case-insensitive, sparse,
multi-value), backed by a **B+ tree** ([`gno.land/p/nt/bptree/v0`](https://github.com/gnolang/gno/tree/master/examples/gno.land/p/nt/bptree)).

A B+ tree packs many entries per persisted node, so each index entry costs
materially less storage and gas than an AVL backing would.

Two operational caveats follow from the in-place-mutating B+ tree backing:

- do **not** mutate the collection (`Set`/`Update`/`Delete`) from inside an index
  iteration callback — a copy-on-write AVL backing would tolerate it, this one
  does not;
- do **not** copy a non-zero `Collection` by value — the copies would share live
  tree nodes while their state diverges.

<!-- BEGIN GNOCONTRACTS FOOTER (generated by `make readmes`; do not edit below) -->

---

Part of **[moul/gno-contracts](https://github.com/moul/gno-contracts)** — moul's versioned gno.land contracts. See the repository for the full catalog, build/test tooling, and usage.

**Dependency graph:**

![gno.land/p/moul/collection/v0 dependency graph](https://raw.githubusercontent.com/moul/gno-contracts/main/_assets/gno.land/p/moul/collection/v0/deps.png)

> ⚠️ **Disclaimer:** provided as-is, without warranty; not security-audited. Full disclaimer: [DISCLAIMER](https://github.com/moul/gno-contracts/blob/main/DISCLAIMER.md).

<!-- END GNOCONTRACTS FOOTER -->