@Override
	public Long ceiling(Long e) {
		return store.safe(lock.readLock(), () -> store.keys.ceiling(direction, e, keySpan));
	}
This is the sub-ranged form of {@link DBCachedObjectStoreKeySubSet}

<p>
For example, this can be obtained via {@code store.asMap().subMap(...).keySet()} or
{@code map.keySet().subSet(...)}.
Ghidra/Debug/ProposedUtils/src/main/java/ghidra/util/database/DBCachedObjectStoreKeySubSet.java