Similar to this question, is IndexedDB guaranteed to be persistent ? ie. Safari will not reclaim disk space if the device is low on memory.
Safari have "No Eviction policy", meaning it will not automatically clean the IndexDB on low disk pressure, without user doing it manually.
IndexDB is one of the fast evolving feature and you can expect to have a different eviction policy any time with no announcement. You should always build with fall back options.
Chrome has explicit persistent storage option which will guarantee no eviction, on user approval for persistent storage and we can expect Safari to do the same sometime, based on their track record of following Chrome in implementing PWA features(though its taking years with super bad documentation).
来源：https://stackoverflow.com/questions/50795409/is-indexeddb-on-safari-guaranteed-to-be-persistent