Add db.getMany(keys) (#214)

Ref Level/community#101

Author: vweevers

index.js

@@ -6,6 +6,7 @@ module.exports = Level
 
 const AbstractLevelDOWN = require('abstract-leveldown').AbstractLevelDOWN
 const inherits = require('inherits')
+const parallel = require('run-parallel-limit')
 const Iterator = require('./iterator')
 const serialize = require('./util/serialize')
 const deserialize = require('./util/deserialize')
@@ -22,7 +23,8 @@ function Level (location, opts) {
     bufferKeys: support.bufferKeys(indexedDB),
     snapshots: true,
     permanence: true,
-    clear: true
+    clear: true,
+    getMany: true
   })
 
   opts = opts || {}
@@ -102,6 +104,32 @@ Level.prototype._get = function (key, options, callback) {
   })
 }
 
+Level.prototype._getMany = function (keys, options, callback) {
+  const asBuffer = options.asBuffer
+  const store = this.store('readonly')
+  const tasks = keys.map((key) => (next) => {
+    let request
+
+    try {
+      request = store.get(key)
+    } catch (err) {
+      return next(err)
+    }
+
+    request.onsuccess = () => {
+      const value = request.result
+      next(null, value === undefined ? value : deserialize(value, asBuffer))
+    }
+
+    request.onerror = (ev) => {
+      ev.stopPropagation()
+      next(request.error)
+    }
+  })
+
+  parallel(tasks, 16, callback)
+}
+
 Level.prototype._del = function (key, options, callback) {
   const store = this.store('readwrite')
   let req

package.json

@@ -23,10 +23,11 @@
     "sauce-labs.svg"
   ],
   "dependencies": {
-    "abstract-leveldown": "^7.0.0",
+    "abstract-leveldown": "^7.2.0",
     "buffer": "^6.0.3",
     "inherits": "^2.0.3",
-    "ltgt": "^2.1.2"
+    "ltgt": "^2.1.2",
+    "run-parallel-limit": "^1.1.0"
   },
   "devDependencies": {
     "airtap": "^4.0.1",

test/index.js

@@ -22,8 +22,9 @@ const testCommon = suite.common({
   // Support of buffer keys depends on environment
   bufferKeys: leveljs(uuid()).supports.bufferKeys,
 
-  // Opt-in to new clear() tests
-  clear: true
+  // Opt-in to new tests
+  clear: true,
+  getMany: true
 })
 
 // Test abstract-leveldown compliance