From 6bec4db11f3a3cca13fd64b60d13629ccf8798c1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Kasper=20Isager=20Dalsgar=C3=B0?= <kasperisager@hey.com>
Date: Tue, 3 Sep 2024 16:06:44 +0200
Subject: [PATCH] Support snapshots before `db.ready()` (#10)

---
 index.js        |  6 ++++--
 lib/batch.js    |  4 ++--
 lib/snapshot.js | 15 +++++++++------
 test.js         | 36 ++++++++++++++++++++++++++++++++++++
 4 files changed, 51 insertions(+), 10 deletions(-)

diff --git a/index.js b/index.js
index 787e2e7..4f5f9fa 100644
--- a/index.js
+++ b/index.js
@@ -76,7 +76,9 @@ const RocksDB = module.exports = class RocksDB extends ReadyResource {
 
     RocksDB._instances.add(this)
 
-    return promise
+    await promise
+
+    for (const snapshot of this._snapshots) snapshot._init()
 
     function onopen (err) {
       if (err) req.reject(new Error(err))
@@ -98,7 +100,7 @@ const RocksDB = module.exports = class RocksDB extends ReadyResource {
 
     RocksDB._instances.delete(this)
 
-    return promise
+    await promise
 
     function onclose (err) {
       if (err) req.reject(new Error(err))
diff --git a/lib/batch.js b/lib/batch.js
index 851a5a3..ca58f70 100644
--- a/lib/batch.js
+++ b/lib/batch.js
@@ -117,7 +117,7 @@ exports.ReadBatch = class RocksDBReadBatch extends RocksDBBatch {
     this._snapshot = snapshot
   }
 
-  async _init () {
+  _init () {
     this._handle = binding.readInit(this)
     this._buffer = binding.readBuffer(this._handle, this._capacity)
   }
@@ -161,7 +161,7 @@ exports.ReadBatch = class RocksDBReadBatch extends RocksDBBatch {
 }
 
 exports.WriteBatch = class RocksDBWriteBatch extends RocksDBBatch {
-  async _init () {
+  _init () {
     this._handle = binding.writeInit(this)
     this._buffer = binding.writeBuffer(this._handle, this._capacity)
   }
diff --git a/lib/snapshot.js b/lib/snapshot.js
index f79008f..8885604 100644
--- a/lib/snapshot.js
+++ b/lib/snapshot.js
@@ -2,22 +2,25 @@ const binding = require('../binding')
 
 module.exports = class RocksDBSnapshot {
   constructor (db) {
-    if (db.opened === false) throw new Error('Database is not open')
-
     this._db = db
+    this._db._snapshots.add(this)
 
-    this._handle = binding.snapshotCreate(db._handle)
+    this._handle = null
 
-    this._db._snapshots.add(this)
+    if (db.opened === true) this._init()
+  }
+
+  _init () {
+    this._handle = binding.snapshotCreate(this._db._handle)
   }
 
   destroy () {
+    this._db._snapshots.delete(this)
+
     if (this._handle === null) return
 
     binding.snapshotDestroy(this._handle)
 
     this._handle = null
-
-    this._db._snapshots.delete(this)
   }
 }
diff --git a/test.js b/test.js
index 1c282ab..d7f2fa9 100644
--- a/test.js
+++ b/test.js
@@ -317,6 +317,42 @@ test('iterator with snapshot', async (t) => {
   await db.close()
 })
 
+test('iterator with snapshot before db open', async (t) => {
+  const db = new RocksDB(await tmp(t))
+
+  const snapshot = db.snapshot()
+
+  await db.ready()
+
+  const batch = db.write()
+  batch.put('aa', 'ba')
+  batch.put('ab', 'bb')
+  batch.put('ac', 'bc')
+  await batch.flush()
+
+  const entries = []
+
+  for await (const entry of db.iterator({ gte: 'a', lt: 'b' }, { snapshot })) {
+    entries.push(entry)
+  }
+
+  snapshot.destroy()
+
+  t.alike(entries, [])
+
+  await db.close()
+})
+
+test('destroy snapshot before db open', async (t) => {
+  const db = new RocksDB(await tmp(t))
+
+  const snapshot = db.snapshot()
+  snapshot.destroy()
+
+  await db.ready()
+  await db.close()
+})
+
 test('peek', async (t) => {
   const db = new RocksDB(await tmp(t))
   await db.ready()