Changelog

All notable, user-visible changes to konserve are documented here.

Unreleased

Added

• PReadMissSafe marker protocol (konserve.impl.storage-layout). A backing store implements it to declare that a read of an absent key is side-effect-free and reports the miss cleanly — its -read-header throws (store-key-not-found-ex store-key) on an absent key, with no side effect. When a backing declares it, io-operation learns existence from the read itself and skips the separate -blob-exists? probe, removing a redundant round-trip (an S3 HEAD before the GET). The default filestore deliberately does not implement it — its -create-blob opens with CREATE and would materialise an empty blob on a probe-free missing read — so filestore behaviour is unchanged. New helpers: store-key-not-found-ex, store-key-not-found?, store-key-not-found.

• dissoc opt :ignore-existence?. dissoc normally probes with -blob-exists? so it can return whether the key existed (true) or was absent (false) — konserve's contract, enforced by the compliance suite. A caller that does not need that boolean (e.g. a GC bulk sweep) can pass {:ignore-existence? true} to skip the probe on a PReadMissSafe backing (whose delete is idempotent), returning true. On non-miss-safe backings the hint is ignored and the probe stays.

• The IndexedDB backend implements PReadMissSafe. A browser read was two IndexedDB transactions — .getKey (the -blob-exists? probe) then .get — and is now a single .get (read-modify-write ops drop their .getKey too). Its -create-blob is side-effect-free and read-blob now signals store-key-not-found-ex on an absent key. (dissoc's single-key fast path also honours :ignore-existence?; the multi-key GC delete path is a separate follow-up.)

Changed

• Probe-elision now covers non-overwrite writes, not only reads. On a PReadMissSafe backing, update-in / update / nested assoc-in / bassoc read the old value read-first (an absent key → a fresh write) instead of a HEAD probe followed by the read. A read-modify-write on an existing key drops from HEAD + GET + PUT to GET + PUT. Pure reads (get / bget / get-meta) were already a single GET on a miss-safe backing.
• konserve.gc/sweep! passes :ignore-existence? on its single-key delete fallback, so GC on a miss-safe store deletes each dead key without a per-key HEAD probe (the batch multi-dissoc path was already probe-free).