diff --git a/README.md b/README.md
index 7ca048c..2384d61 100755
--- a/README.md
+++ b/README.md
@@ -144,7 +144,7 @@ If the document does not contain an `_id` field, NeDB will automatically
 generate one for you (a 16-characters alphanumerical string). The `_id` of a
 document, once set, cannot be modified.
 
-Field names cannot begin by '$' or contain a '.'.
+Field names cannot start with '$' or contain the characters '.' and ','.
 
 ```javascript
 const doc = {
@@ -698,6 +698,15 @@ fields in nested documents using the dot notation. For now, indexes are only
 used to speed up basic queries and queries using `$in`, `$lt`, `$lte`, `$gt`
 and `$gte`. The indexed values cannot be of type array of object.
 
+**Breaking change**: [since v3.2.0](./CHANGELOG.md), comma can no longer be used in indexed field names.
+
+The following is illegal:
+```javascript
+db.ensureIndexAsync({ fieldName: 'some,field' })
+db.ensureIndexAsync({ fieldName: ['some,field', 'other,field'] })
+```
+This is a side effect of the compound index implementation.
+
 To create an index, use [`datastore#ensureIndexAsync(options)`](./API.md#Datastore+ensureIndexAsync).
 It resolves when the index is persisted on disk (if the database is persistent)
 and may throw an Error (usually a unique constraint that was violated). It can
@@ -705,7 +714,7 @@ be called when you want, even after some data was inserted, though it's best to
 call it at application startup. The options are:
 
 * **fieldName** (required): name of the field to index. Use the dot notation to
-  index a field in a nested document.
+  index a field in a nested document. For a compound index, use an array of field names.
 * **unique** (optional, defaults to `false`): enforce field uniqueness.
 * **sparse** (optional, defaults to `false`): don't index documents for which
   the field is not defined.
@@ -735,6 +744,9 @@ await db.ensureIndexAsync({
   sparse: true
 })
 
+// Using a compound index
+await db.ensureIndexAsync({ fieldName: ["field1", "field2"] });
+
 try {
   // Format of the error message when the unique constraint is not met
   await db.insertAsync({ somefield: '@seald-io/nedb' })
diff --git a/index.d.ts b/index.d.ts
index b3059ab..0be859e 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -42,9 +42,9 @@ declare class Nedb<G = any> extends EventEmitter {
 
   ensureIndexAsync(options: Nedb.EnsureIndexOptions): Promise<void>;
 
-  removeIndex(fieldName: string, callback?: (err: Error | null) => void): void;
+  removeIndex(fieldName: string | string[], callback?: (err: Error | null) => void): void;
 
-  removeIndexAsync(fieldName: string): Promise<void>;
+  removeIndexAsync(fieldName: string | string[]): Promise<void>;
 
   insert<T extends G>(newDoc: T, callback?: (err: Error | null, document: T) => void): void;
   insert<T extends G>(newDocs: T[], callback?: (err: Error | null, documents: T[]) => void): void;
@@ -128,7 +128,7 @@ declare namespace Nedb {
   }
 
   interface EnsureIndexOptions {
-    fieldName: string;
+    fieldName: string | string[];
     unique?: boolean;
     sparse?: boolean;
     expireAfterSeconds?: number;
diff --git a/lib/datastore.js b/lib/datastore.js
index 1eabc88..1a6aa48 100755
--- a/lib/datastore.js
+++ b/lib/datastore.js
@@ -6,7 +6,7 @@ const Executor = require('./executor.js')
 const Index = require('./indexes.js')
 const model = require('./model.js')
 const Persistence = require('./persistence.js')
-const { isDate } = require('./utils.js')
+const { isDate, pick, filterIndexNames } = require('./utils.js')
 
 /**
  * Callback with no parameter
@@ -431,7 +431,7 @@ class Datastore extends EventEmitter {
   /**
    * Callback version of {@link Datastore#ensureIndex}.
    * @param {object} options
-   * @param {string} options.fieldName
+   * @param {string|string[]} options.fieldName
    * @param {boolean} [options.unique = false]
    * @param {boolean} [options.sparse = false]
    * @param {number} [options.expireAfterSeconds]
@@ -448,8 +448,8 @@ class Datastore extends EventEmitter {
    * This function acts synchronously on the indexes, however the persistence of the indexes is deferred with the
    * executor.
    * @param {object} options
-   * @param {string} options.fieldName Name of the field to index. Use the dot notation to index a field in a nested
-   * document.
+   * @param {string|string[]} options.fieldName Name of the field to index. Use the dot notation to index a field in a nested
+   * document. For a compound index, use an array of field names. Using a comma in a field name is not permitted.
    * @param {boolean} [options.unique = false] Enforce field uniqueness. Note that a unique index will raise an error
    * if you try to index two documents for which the field is not defined.
    * @param {boolean} [options.sparse = false] Don't index documents for which the field is not defined. Use this option
@@ -465,20 +465,32 @@ class Datastore extends EventEmitter {
       err.missingFieldName = true
       throw err
     }
-    if (this.indexes[options.fieldName]) return
 
-    this.indexes[options.fieldName] = new Index(options)
-    if (options.expireAfterSeconds !== undefined) this.ttlIndexes[options.fieldName] = options.expireAfterSeconds // With this implementation index creation is not necessary to ensure TTL but we stick with MongoDB's API here
+    const _fields = [].concat(options.fieldName).sort()
+
+    if (_fields.some(field => field.includes(','))) {
+      throw new Error('Cannot use comma in index fieldName')
+    }
+
+    const _options = {
+      ...options,
+      fieldName: _fields.join(',')
+    }
+
+    if (this.indexes[_options.fieldName]) return
+
+    this.indexes[_options.fieldName] = new Index(_options)
+    if (options.expireAfterSeconds !== undefined) this.ttlIndexes[_options.fieldName] = _options.expireAfterSeconds // With this implementation index creation is not necessary to ensure TTL but we stick with MongoDB's API here
 
     try {
-      this.indexes[options.fieldName].insert(this.getAllData())
+      this.indexes[_options.fieldName].insert(this.getAllData())
     } catch (e) {
-      delete this.indexes[options.fieldName]
+      delete this.indexes[_options.fieldName]
       throw e
     }
 
     // We may want to force all options to be persisted including defaults, not just the ones passed the index creation function
-    await this.executor.pushAsync(() => this.persistence.persistNewStateAsync([{ $$indexCreated: options }]), true)
+    await this.executor.pushAsync(() => this.persistence.persistNewStateAsync([{ $$indexCreated: _options }]), true)
   }
 
   /**
@@ -598,16 +610,27 @@ class Datastore extends EventEmitter {
    */
   _getRawCandidates (query) {
     const indexNames = Object.keys(this.indexes)
+
     // STEP 1: get candidates list by checking indexes from most to least frequent usecase
     // For a basic match
+
     let usableQuery
     usableQuery = Object.entries(query)
-      .filter(([k, v]) =>
-        !!(typeof v === 'string' || typeof v === 'number' || typeof v === 'boolean' || isDate(v) || v === null) &&
-        indexNames.includes(k)
-      )
+      .filter(filterIndexNames(indexNames))
       .pop()
     if (usableQuery) return this.indexes[usableQuery[0]].getMatching(usableQuery[1])
+
+    // For a compound match
+    const compoundQueryKeys = indexNames
+      .filter(indexName => indexName.indexOf(',') !== -1)
+      .map(indexName => indexName.split(','))
+      .filter(subIndexNames =>
+        Object.entries(query)
+          .filter(filterIndexNames(subIndexNames)).length === subIndexNames.length
+      )
+
+    if (compoundQueryKeys.length > 0) return this.indexes[compoundQueryKeys[0]].getMatching(pick(query, compoundQueryKeys[0]))
+
     // For a $in match
     usableQuery = Object.entries(query)
       .filter(([k, v]) =>
diff --git a/lib/indexes.js b/lib/indexes.js
index fee3ccc..a0335ea 100755
--- a/lib/indexes.js
+++ b/lib/indexes.js
@@ -38,16 +38,26 @@ class Index {
    * All methods on an index guarantee that either the whole operation was successful and the index changed
    * or the operation was unsuccessful and an error is thrown while the index is unchanged
    * @param {object} options
-   * @param {string} options.fieldName On which field should the index apply (can use dot notation to index on sub fields)
+   * @param {string} options.fieldName On which field should the index apply, can use dot notation to index on sub fields, can use comma-separated notation to use compound indexes
    * @param {boolean} [options.unique = false] Enforces a unique constraint
    * @param {boolean} [options.sparse = false] Allows a sparse index (we can have documents for which fieldName is `undefined`)
    */
   constructor (options) {
     /**
-     * On which field the index applies to (may use dot notation to index on sub fields).
+     * On which field the index applies to, can use dot notation to index on sub fields, can use comma-separated notation to use compound indexes.
      * @type {string}
      */
     this.fieldName = options.fieldName
+
+    if (typeof this.fieldName !== 'string') throw new Error('fieldName must be a string')
+
+    /**
+     * Internal property which is an Array representing the fieldName split with `,`, useful only for compound indexes.
+     * @type {string[]}
+     * @private
+     */
+    this._fields = this.fieldName.split(',')
+
     /**
      * Defines if the index enforces a unique constraint for this index.
      * @type {boolean}
@@ -99,10 +109,10 @@ class Index {
       return
     }
 
-    const key = model.getDotValue(doc, this.fieldName)
+    const key = model.getDotValues(doc, this._fields)
 
     // We don't index documents that don't contain the field if the index is sparse
-    if (key === undefined && this.sparse) return
+    if ((key === undefined || (typeof key === 'object' && key !== null && Object.values(key).every(el => el === undefined))) && this.sparse) return
 
     if (!Array.isArray(key)) this.tree.insert(key, doc)
     else {
@@ -171,8 +181,7 @@ class Index {
       return
     }
 
-    const key = model.getDotValue(doc, this.fieldName)
-
+    const key = model.getDotValues(doc, this._fields)
     if (key === undefined && this.sparse) return
 
     if (!Array.isArray(key)) {
diff --git a/lib/model.js b/lib/model.js
index b310f07..ca9fd89 100755
--- a/lib/model.js
+++ b/lib/model.js
@@ -503,6 +503,20 @@ const getDotValue = (obj, field) => {
   } else return getDotValue(obj[fieldParts[0]], fieldParts.slice(1))
 }
 
+/**
+ * Get dot values for either a bunch of fields or just one.
+ */
+const getDotValues = (obj, fields) => {
+  if (!Array.isArray(fields)) throw new Error('fields must be an Array')
+  if (fields.length > 1) {
+    const key = {}
+    for (const field of fields) {
+      key[field] = getDotValue(obj, field)
+    }
+    return key
+  } else return getDotValue(obj, fields[0])
+}
+
 /**
  * Check whether 'things' are equal
  * Things are defined as any native types (string, number, boolean, null, date) and objects
@@ -807,6 +821,7 @@ module.exports.checkObject = checkObject
 module.exports.isPrimitiveType = isPrimitiveType
 module.exports.modify = modify
 module.exports.getDotValue = getDotValue
+module.exports.getDotValues = getDotValues
 module.exports.match = match
 module.exports.areThingsEqual = areThingsEqual
 module.exports.compareThings = compareThings
diff --git a/lib/persistence.js b/lib/persistence.js
index 5f96d0a..c704a7c 100755
--- a/lib/persistence.js
+++ b/lib/persistence.js
@@ -107,7 +107,7 @@ class Persistence {
       if (fieldName !== '_id') { // The special _id index is managed by datastore.js, the others need to be persisted
         lines.push(this.afterSerialization(model.serialize({
           $$indexCreated: {
-            fieldName: fieldName,
+            fieldName: this.db.indexes[fieldName].fieldName,
             unique: this.db.indexes[fieldName].unique,
             sparse: this.db.indexes[fieldName].sparse
           }
diff --git a/lib/utils.js b/lib/utils.js
index 951df8f..9641972 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -58,6 +58,27 @@ const isDate = d => isObject(d) && Object.prototype.toString.call(d) === '[objec
  */
 const isRegExp = re => isObject(re) && Object.prototype.toString.call(re) === '[object RegExp]'
 
+/**
+ * return a copy of the object that filtered using the given keys
+ *
+ * @param {*} object
+ * @param {*} keys
+ * @returns
+ */
+const pick = (object, keys) => {
+  return keys.reduce((obj, key) => {
+    if (object && Object.prototype.hasOwnProperty.call(object, key)) {
+      obj[key] = object[key]
+    }
+    return obj
+  }, {})
+}
+
+const filterIndexNames = (indexNames) => ([k, v]) => !!(typeof v === 'string' || typeof v === 'number' || typeof v === 'boolean' || isDate(v) || v === null) &&
+indexNames.includes(k)
+
 module.exports.uniq = uniq
 module.exports.isDate = isDate
 module.exports.isRegExp = isRegExp
+module.exports.pick = pick
+module.exports.filterIndexNames = filterIndexNames
diff --git a/test/db.async.test.js b/test/db.async.test.js
index 3da4b26..45cb76e 100644
--- a/test/db.async.test.js
+++ b/test/db.async.test.js
@@ -309,6 +309,18 @@ describe('Database async', function () {
       assert.deepEqual(doc2, { _id: doc2._id, tf: 4, an: 'other' })
     })
 
+    it('Can use a compound index to get docs with a basic match', async () => {
+      await d.ensureIndexAsync({ fieldName: ['tf', 'tg'] })
+      await d.insertAsync({ tf: 4, tg: 0, foo: 1 })
+      await d.insertAsync({ tf: 6, tg: 0, foo: 2 })
+      const _doc1 = await d.insertAsync({ tf: 4, tg: 1, foo: 3 })
+      await d.insertAsync({ tf: 6, tg: 1, foo: 4 })
+      const data = await d._getCandidatesAsync({ tf: 4, tg: 1 })
+      const doc1 = data.find(d => d._id === _doc1._id)
+      assert.equal(data.length, 1)
+      assert.deepEqual(doc1, { _id: doc1._id, tf: 4, tg: 1, foo: 3 })
+    })
+
     it('Can use an index to get docs with a $in match', async () => {
       await d.ensureIndexAsync({ fieldName: 'tf' })
       await d.insertAsync({ tf: 4 })
@@ -1290,7 +1302,7 @@ describe('Database async', function () {
         assert.equal(d.indexes.z.tree.search('3')[0], d.getAllData()[2])
       })
 
-      it('ensureIndex can be called twice on the same field, the second call will ahve no effect', async () => {
+      it('ensureIndex can be called twice on the same field, the second call will have no effect', async () => {
         assert.equal(Object.keys(d.indexes).length, 1)
         assert.equal(Object.keys(d.indexes)[0], '_id')
 
@@ -1315,6 +1327,67 @@ describe('Database async', function () {
         assert.equal(d.indexes.planet.getAll().length, 2)
       })
 
+      it('ensureIndex can be called twice on the same compound field, the second call will have no effect', async () => {
+        assert.equal(Object.keys(d.indexes).length, 1)
+        assert.equal(Object.keys(d.indexes)[0], '_id')
+
+        await d.insertAsync({ star: 'sun', planet: 'Earth' })
+        await d.insertAsync({ star: 'sun', planet: 'Mars' })
+        const docs = await d.findAsync({})
+        assert.equal(docs.length, 2)
+
+        await d.ensureIndexAsync({ fieldName: ['star', 'planet'] })
+        assert.equal(Object.keys(d.indexes).length, 2)
+        assert.equal(Object.keys(d.indexes)[0], '_id')
+        assert.equal(Object.keys(d.indexes)[1], 'planet,star')
+
+        assert.equal(d.indexes['planet,star'].getAll().length, 2)
+
+        // This second call has no effect, documents don't get inserted twice in the index
+        await d.ensureIndexAsync({ fieldName: ['star', 'planet'] })
+        assert.equal(Object.keys(d.indexes).length, 2)
+        assert.equal(Object.keys(d.indexes)[0], '_id')
+        assert.equal(Object.keys(d.indexes)[1], 'planet,star')
+
+        assert.equal(d.indexes['planet,star'].getAll().length, 2)
+      })
+
+      it('ensureIndex can be called twice on the same compound field with a different order, the second call will have no effect', async () => {
+        assert.equal(Object.keys(d.indexes).length, 1)
+        assert.equal(Object.keys(d.indexes)[0], '_id')
+
+        await d.insertAsync({ star: 'sun', planet: 'Earth' })
+        await d.insertAsync({ star: 'sun', planet: 'Mars' })
+        const docs = await d.findAsync({})
+        assert.equal(docs.length, 2)
+
+        await d.ensureIndexAsync({ fieldName: ['star', 'planet'] })
+        assert.equal(Object.keys(d.indexes).length, 2)
+        assert.equal(Object.keys(d.indexes)[0], '_id')
+        assert.equal(Object.keys(d.indexes)[1], 'planet,star')
+
+        assert.equal(d.indexes['planet,star'].getAll().length, 2)
+
+        // This second call has no effect, documents don't get inserted twice in the index
+        await d.ensureIndexAsync({ fieldName: ['planet', 'star'] })
+        assert.equal(Object.keys(d.indexes).length, 2)
+        assert.equal(Object.keys(d.indexes)[0], '_id')
+        assert.equal(Object.keys(d.indexes)[1], 'planet,star')
+
+        assert.equal(d.indexes['planet,star'].getAll().length, 2)
+      })
+
+      it('ensureIndex cannot be called with an illegal field name', async () => {
+        await assert.rejects(() => d.ensureIndexAsync({ fieldName: 'star,planet' }), err => {
+          assert.notEqual(err, null)
+          return true
+        })
+        await assert.rejects(() => d.ensureIndexAsync({ fieldName: ['star,planet', 'other'] }), err => {
+          assert.notEqual(err, null)
+          return true
+        })
+      })
+
       it('ensureIndex can be called after the data set was modified and the index still be correct', async () => {
         const rawData = model.serialize({ _id: 'aaa', z: '1', a: 2, ages: [1, 5, 12] }) + '\n' +
           model.serialize({ _id: 'bbb', z: '2', hello: 'world' })
diff --git a/test/db.test.js b/test/db.test.js
index 70c9561..40d1ffa 100755
--- a/test/db.test.js
+++ b/test/db.test.js
@@ -490,6 +490,30 @@ describe('Database', function () {
       })
     })
 
+    it('Can use a compound index to get docs with a basic match', function (done) {
+      // eslint-disable-next-line node/handle-callback-err
+      d.ensureIndex({ fieldName: ['tf', 'tg'] }, function (err) {
+        d.insert({ tf: 4, tg: 0, foo: 1 }, function () {
+          d.insert({ tf: 6, tg: 0, foo: 2 }, function () {
+            // eslint-disable-next-line node/handle-callback-err
+            d.insert({ tf: 4, tg: 1, foo: 3 }, function (err, _doc1) {
+              d.insert({ tf: 6, tg: 1, foo: 4 }, function () {
+                // eslint-disable-next-line node/handle-callback-err
+                callbackify(query => d._getCandidatesAsync(query))({ tf: 4, tg: 1 }, function (err, data) {
+                  const doc1 = data.find(function (d) { return d._id === _doc1._id })
+
+                  data.length.should.equal(1)
+                  assert.deepEqual(doc1, { _id: doc1._id, tf: 4, tg: 1, foo: 3 })
+
+                  done()
+                })
+              })
+            })
+          })
+        })
+      })
+    })
+
     it('Can use an index to get docs with a $in match', function (done) {
       // eslint-disable-next-line node/handle-callback-err
       d.ensureIndex({ fieldName: 'tf' }, function (err) {
@@ -2082,7 +2106,7 @@ describe('Database', function () {
         })
       })
 
-      it('ensureIndex can be called twice on the same field, the second call will ahve no effect', function (done) {
+      it('ensureIndex can be called twice on the same field, the second call will have no effect', function (done) {
         Object.keys(d.indexes).length.should.equal(1)
         Object.keys(d.indexes)[0].should.equal('_id')
 
@@ -2117,6 +2141,86 @@ describe('Database', function () {
         })
       })
 
+      it('ensureIndex can be called twice on the same compound fields, the second call will have no effect', function (done) {
+        Object.keys(d.indexes).length.should.equal(1)
+        Object.keys(d.indexes)[0].should.equal('_id')
+
+        d.insert({ star: 'sun', planet: 'Earth' }, function () {
+          d.insert({ star: 'sun', planet: 'Mars' }, function () {
+            // eslint-disable-next-line node/handle-callback-err
+            d.find({}, function (err, docs) {
+              docs.length.should.equal(2)
+
+              d.ensureIndex({ fieldName: ['star', 'planet'] }, function (err) {
+                assert.isNull(err)
+                Object.keys(d.indexes).length.should.equal(2)
+                Object.keys(d.indexes)[0].should.equal('_id')
+                Object.keys(d.indexes)[1].should.equal('planet,star')
+
+                d.indexes['planet,star'].getAll().length.should.equal(2)
+
+                // This second call has no effect, documents don't get inserted twice in the index
+                d.ensureIndex({ fieldName: ['star', 'planet'] }, function (err) {
+                  assert.isNull(err)
+                  Object.keys(d.indexes).length.should.equal(2)
+                  Object.keys(d.indexes)[0].should.equal('_id')
+                  Object.keys(d.indexes)[1].should.equal('planet,star')
+
+                  d.indexes['planet,star'].getAll().length.should.equal(2)
+
+                  done()
+                })
+              })
+            })
+          })
+        })
+      })
+
+      it('ensureIndex can be called twice on the same compound fields with a different order, the second call will have no effect', function (done) {
+        Object.keys(d.indexes).length.should.equal(1)
+        Object.keys(d.indexes)[0].should.equal('_id')
+
+        d.insert({ star: 'sun', planet: 'Earth' }, function () {
+          d.insert({ star: 'sun', planet: 'Mars' }, function () {
+            // eslint-disable-next-line node/handle-callback-err
+            d.find({}, function (err, docs) {
+              docs.length.should.equal(2)
+
+              d.ensureIndex({ fieldName: ['star', 'planet'] }, function (err) {
+                assert.isNull(err)
+                Object.keys(d.indexes).length.should.equal(2)
+                Object.keys(d.indexes)[0].should.equal('_id')
+                Object.keys(d.indexes)[1].should.equal('planet,star')
+
+                d.indexes['planet,star'].getAll().length.should.equal(2)
+
+                // This second call has no effect, documents don't get inserted twice in the index
+                d.ensureIndex({ fieldName: ['planet', 'star'] }, function (err) {
+                  assert.isNull(err)
+                  Object.keys(d.indexes).length.should.equal(2)
+                  Object.keys(d.indexes)[0].should.equal('_id')
+                  Object.keys(d.indexes)[1].should.equal('planet,star')
+
+                  d.indexes['planet,star'].getAll().length.should.equal(2)
+
+                  done()
+                })
+              })
+            })
+          })
+        })
+      })
+
+      it('ensureIndex cannot be called with an illegal field name', function (done) {
+        d.ensureIndex({ fieldName: 'star,planet' }, function (err) {
+          assert.isNotNull(err)
+          d.ensureIndex({ fieldName: ['star,planet', 'other'] }, function (err) {
+            assert.isNotNull(err)
+            done()
+          })
+        })
+      })
+
       it('ensureIndex can be called after the data set was modified and the index still be correct', function (done) {
         const rawData = model.serialize({ _id: 'aaa', z: '1', a: 2, ages: [1, 5, 12] }) + '\n' +
           model.serialize({ _id: 'bbb', z: '2', hello: 'world' })
diff --git a/test/indexes.test.js b/test/indexes.test.js
index ef45dba..7720619 100755
--- a/test/indexes.test.js
+++ b/test/indexes.test.js
@@ -29,6 +29,28 @@ describe('Indexes', function () {
       doc3.a.should.equal(42)
     })
 
+    it('Can insert pointers to documents in the index correctly when they have compound fields', function () {
+      const idx = new Index({ fieldName: 'tf,tg' })
+      const doc1 = { a: 5, tf: 'hello', tg: 'world' }
+      const doc2 = { a: 8, tf: 'hello', tg: 'bloup' }
+      const doc3 = { a: 2, tf: 'bloup', tg: 'bloup' }
+
+      idx.insert(doc1)
+      idx.insert(doc2)
+      idx.insert(doc3)
+
+      // The underlying BST now has 3 nodes which contain the docs where it's expected
+      idx.tree.getNumberOfKeys().should.equal(3)
+      assert.deepEqual(idx.tree.search({ tf: 'hello', tg: 'world' }), [{ a: 5, tf: 'hello', tg: 'world' }])
+      assert.deepEqual(idx.tree.search({ tf: 'hello', tg: 'bloup' }), [{ a: 8, tf: 'hello', tg: 'bloup' }])
+      assert.deepEqual(idx.tree.search({ tf: 'bloup', tg: 'bloup' }), [{ a: 2, tf: 'bloup', tg: 'bloup' }])
+
+      // The nodes contain pointers to the actual documents
+      idx.tree.search({ tf: 'hello', tg: 'bloup' })[0].should.equal(doc2)
+      idx.tree.search({ tf: 'bloup', tg: 'bloup' })[0].a = 42
+      doc3.a.should.equal(42)
+    })
+
     it('Inserting twice for the same fieldName in a unique index will result in an error thrown', function () {
       const idx = new Index({ fieldName: 'tf', unique: true })
       const doc1 = { a: 5, tf: 'hello' }
@@ -58,6 +80,25 @@ describe('Indexes', function () {
       idx.tree.getNumberOfKeys().should.equal(0) // Docs are not indexed
     })
 
+    it('Inserting twice for the same compound fieldName in a unique index will result in an error thrown', function () {
+      const idx = new Index({ fieldName: 'tf,tg', unique: true })
+      const doc1 = { a: 5, tf: 'hello', tg: 'world' }
+
+      idx.insert(doc1)
+      idx.tree.getNumberOfKeys().should.equal(1);
+      (function () { idx.insert(doc1) }).should.throw()
+    })
+
+    it('Inserting twice for a compound fieldName the docs dont have with a unique and sparse index will not throw, since the docs will be non indexed', function () {
+      const idx = new Index({ fieldName: 'nope,nopeNope', unique: true, sparse: true })
+      const doc1 = { a: 5, tf: 'hello' }
+      const doc2 = { a: 5, tf: 'world' }
+
+      idx.insert(doc1)
+      idx.insert(doc2)
+      idx.tree.getNumberOfKeys().should.equal(0) // Docs are not indexed
+    })
+
     it('Works with dot notation', function () {
       const idx = new Index({ fieldName: 'tf.nested' })
       const doc1 = { a: 5, tf: { nested: 'hello' } }
@@ -202,6 +243,30 @@ describe('Indexes', function () {
         idx.getMatching('ee').length.should.equal(0)
       })
     }) // ==== End of 'Array fields' ==== //
+
+    describe('Compound Indexes', function () {
+      it('Supports field names separated by commas', function () {
+        const idx = new Index({ fieldName: 'tf,tf2' })
+        const doc1 = { a: 5, tf: 'hello', tf2: 7 }
+        const doc2 = { a: 8, tf: 'hello', tf2: 6 }
+        const doc3 = { a: 2, tf: 'bloup', tf2: 3 }
+
+        idx.insert(doc1)
+        idx.insert(doc2)
+        idx.insert(doc3)
+
+        // The underlying BST now has 3 nodes which contain the docs where it's expected
+        idx.tree.getNumberOfKeys().should.equal(3)
+        assert.deepEqual(idx.tree.search({ tf: 'hello', tf2: 7 }), [{ a: 5, tf: 'hello', tf2: 7 }])
+        assert.deepEqual(idx.tree.search({ tf: 'hello', tf2: 6 }), [{ a: 8, tf: 'hello', tf2: 6 }])
+        assert.deepEqual(idx.tree.search({ tf: 'bloup', tf2: 3 }), [{ a: 2, tf: 'bloup', tf2: 3 }])
+
+        // The nodes contain pointers to the actual documents
+        idx.tree.search({ tf: 'hello', tf2: 6 })[0].should.equal(doc2)
+        idx.tree.search({ tf: 'bloup', tf2: 3 })[0].a = 42
+        doc3.a.should.equal(42)
+      })
+    })
   }) // ==== End of 'Insertion' ==== //
 
   describe('Removal', function () {