Add support for RocksDB (dramatic memory improvement with multiple databases)

packages/pouchdb-adapter-asyncstorage/readme.md

@@ -24,6 +24,11 @@ db.get('4711')
 
 ```
 
+### Memory
+
+Be careful when using this with other AsyncStorage data or multiple databases as it loads *all* keys in your store into memory. You can use [react-native-async-storage-rocks](https://github.com/tradle/react-native-async-storage-rocks) if this is an issue for you (see below).
+
+
 ### Android limit
 
 On Android asyncstorage has a limitation of 6 MB per default, you might want to increase it
@@ -34,6 +39,11 @@ long size = 50L * 1024L * 1024L; // 50 MB
 com.facebook.react.modules.storage.ReactDatabaseSupplier.getInstance(getApplicationContext()).setMaximumSize(size);
 ```
 
+### RocksDB
+
+If you are using [react-native-async-storage-rocks](https://github.com/tradle/react-native-async-storage-rocks) then pouchdb-adapter-asyncstorage will detect and use the native `getKeysWithPrefix` method for memory-efficient key lookups.
+
+
 For full API documentation and guides on PouchDB, see [PouchDB.com](http://pouchdb.com/). For details on PouchDB sub-packages, see the [Custom Builds documentation](http://pouchdb.com/custom.html).
 
 ---

packages/pouchdb-adapter-asyncstorage/src/asyncstorage_core.js

@@ -7,18 +7,43 @@
 import { AsyncStorage } from 'react-native'
 import { safeJsonParse, safeJsonStringify } from 'pouchdb-json'
 
+
+let AsyncStorageRocksDB
+try {
+  AsyncStorageRocksDB = require('react-native-async-storage-rocks').default
+} finally {
+  // Fall back to regular AsyncStorage
+}
+
+
 function createPrefix(dbName) {
   return dbName.replace(/!/g, '!!') + '!' // escape bangs in dbName
 }
 
 function prepareKey(key, core) {
-  return (
-    core._prefix +
-    key
-      .replace(/\u0002/g, '\u0002\u0002')
-      .replace(/\u0001/g, '\u0001\u0002')
-      .replace(/\u0000/g, '\u0001\u0001')
-  )
+  key = key
+    .replace(/\u0002/g, '\u0002\u0002')
+    .replace(/\u0001/g, '\u0001\u0002')
+    .replace(/\u0000/g, '\u0001\u0001')
+
+  if (AsyncStorageRocksDB) {
+    key = key.replace(/ÿ/g, '\u0003') // RocksDB can't handle ÿ
+  }
+
+  return core._prefix + key
+}
+
+function unescapeKey(key) {
+  key = key
+    .replace(/\u0001\u0001/g, '\u0000')
+    .replace(/\u0001\u0002/g, '\u0001')
+    .replace(/\u0002\u0002/g, '\u0002')
+
+  if (AsyncStorageRocksDB) {
+    key = key.replace(/\u0003/g, 'ÿ')
+  }
+
+  return key
 }
 
 function AsyncStorageCore(dbName) {
@@ -30,24 +55,32 @@ AsyncStorageCore.prototype.getKeys = function(callback) {
   const prefix = this._prefix
   const prefixLen = prefix.length
 
-  AsyncStorage.getAllKeys((error, allKeys) => {
-    if (error) return callback(error)
+  if (AsyncStorageRocksDB) {
+
+    // getAllKeysWithPrefix is dramatically more memory efficient if there are other items
+    // stored that are not part of the current database (eg other databases or app data).
+    // getAllKeys causes memory to increase linearly with the total number of keys.
+    AsyncStorageRocksDB.getAllKeysWithPrefix(prefix, (error, allKeys) => {
+      if (error) return callback(error)
 
-    allKeys.forEach(fullKey => {
-      if (fullKey.slice(0, prefixLen) === prefix) {
-        keys.push(
-          fullKey
-            .slice(prefixLen)
-            .replace(/\u0001\u0001/g, '\u0000')
-            .replace(/\u0001\u0002/g, '\u0001')
-            .replace(/\u0002\u0002/g, '\u0002')
-        )
-      }
+      allKeys.forEach(fullKey => keys.push(unescapeKey(fullKey)))
     })
 
-    keys.sort()
-    callback(null, keys)
-  })
+  } else {
+
+    AsyncStorage.getAllKeys((error, allKeys) => {
+      if (error) return callback(error)
+
+      allKeys.forEach(fullKey => {
+        if (fullKey.slice(0, prefixLen) === prefix) {
+          keys.push(unescapeKey(fullKey.slice(prefixLen)))
+        }
+      })
+    })
+  }
+
+  keys.sort()
+  callback(null, keys)
 }
 
 const stringifyValue = value => {
@@ -114,4 +147,4 @@ AsyncStorageCore.destroy = function(dbName, callback) {
   })
 }
 
-module.exports = AsyncStorageCore
+module.exports = AsyncStorageCore