message: Re-add the LRU removal (higher-level)
diff: import { DiskStore } from './types';
  import { AbstractLevelDOWN } from 'abstract-leveldown';
  -import { LRUMap } from 'lru_map';
  +// import { LRUMap } from 'lru_map';
  import isUndefined from '@polkadot/util/is/undefined';
  import logger from '@polkadot/util/logger';
  import Combined from './store/Combined';
  -const LRU_SIZE = 16384;
  +// const LRU_SIZE = 16384;
  const KEY_LENGTH = 32;
  const l = logger('disk/scatter');
  @@ -20,13 +20,13 @@ const noop = () =>
  class DiskDown extends AbstractLevelDOWN {
  _disk: DiskStore;
  - _store: LRUMap<string, Buffer>;
  + // _store: LRUMap<string, Buffer>;
  constructor (location: string) {
  super(location);
  this._disk = new Combined(location);
  - this._store = new LRUMap(LRU_SIZE);
  + // this._store = new LRUMap(LRU_SIZE);
  }
  compact (progress: (message: string) => void): void {
  @@ -73,7 +73,7 @@ class DiskDown extends AbstractLevelDOWN {
  _del (key: Buffer, options: any, callback: Function) {
  l.debug(() => ['_del', key]);
  - this._store.delete(key.toString());
  + // this._store.delete(key.toString());
  this._disk.delete(key);
  process.nextTick(callback);
  @@ -82,7 +82,10 @@ class DiskDown extends AbstractLevelDOWN {
  _get (key: Buffer, options: any, callback: Function) {
  l.debug(() => ['_get', key.toString('hex')]);
  - const value = this._store.get(key.toString()) || this._disk.get(key);
  + // FIXME _If_ LRU is re-instated, it needs to get set once a value is
  + // retrieved from disk. (As of now, not needed since removed)
  + // const value = this._store.get(key.toString()) || this._disk.get(key);
  + const value = this._disk.get(key);
  if (isUndefined(value)) {
  process.nextTick(callback, new Error('NotFound'));
  @@ -95,7 +98,7 @@ class DiskDown extends AbstractLevelDOWN {
  _put (key: Buffer, value: Buffer, options: any, callback: Function) {
  l.debug(() => ['_put', key.toString('hex'), value]);
  - this._store.set(key.toString(), value);
  + // this._store.set(key.toString(), value);
  this._disk.set(key, value);
  process.nextTick(callback);
  