rocksdb: use storage API for updating dependency (#610)

* add test for snapshot on named batch

* move dependency mutation to storage api

lib/core.js

@@ -413,7 +413,7 @@ module.exports = class Core {
 
         await state.flushWriteBatch(storage)
 
-        if (dependency) state.refreshDependencies(dependency)
+        if (dependency) state.storage.updateDependencies(dependency.length)
       }
 
       if (this.header.hints.contiguousLength === treeLength) {

lib/session-state.js

@@ -129,24 +129,6 @@ module.exports = class SessionState {
     return dependency
   }
 
-  refreshDependencies (dependency) {
-    assert(!this.isDefault(), 'Default state should have no dependencies')
-
-    const deps = this.storage.dependencies
-
-    for (let i = deps.length - 1; i >= 0; i--) {
-      if (deps[i].data === dependency.data) {
-        const updated = deps.slice(0, i)
-        updated.push(dependency)
-
-        this.storage.dependencies = updated
-        return
-      }
-    }
-
-    throw new Error('Dependency not found')
-  }
-
   _clearActiveBatch (err) {
     if (!this._activeBatch) return
     this._activeBatch.destroy()
@@ -271,7 +253,7 @@ module.exports = class SessionState {
 
       await this.flushWriteBatch(storage)
 
-      if (dependency) this.refreshDependencies(dependency)
+      if (dependency) this.storage.updateDependencies(dependency.length)
       this.tree.onupdate(treeUpdate)
 
       this.ontruncate(tree, tree.length, batch.treeLength)
@@ -292,7 +274,7 @@ module.exports = class SessionState {
 
       await this.flushWriteBatch(storage)
 
-      if (dependency) this.refreshDependencies(dependency)
+      if (dependency) this.storage.updateDependencies(dependency.length)
       this.tree.onupdate(treeUpdate)
 
       this.ontruncate(tree, batch.ancestors, batch.treeLength)
@@ -341,7 +323,7 @@ module.exports = class SessionState {
 
       await this.flushWriteBatch(storage)
 
-      if (dependency) this.refreshDependencies(dependency)
+      if (dependency) this.storage.updateDependencies(dependency.length)
 
       if (this.isDefault()) {
         const length = end - start
@@ -635,18 +617,11 @@ async function storeBitfieldRange (storage, writer, from, to, value) {
 }
 
 function updateDependency (state, length) {
-  const dependencies = state.storage.dependencies
-  if (!dependencies.length) return null // skip default state and overlays of default
-
-  let target = dependencies[dependencies.length - 1]
-
-  for (const dep of dependencies) {
-    if (dep.length < length) break
-    target = dep
-  }
+  const dependency = state.storage.findDependency(length)
+  if (dependency === null) return null // skip default state and overlays of default
 
   return {
-    data: target.data,
+    data: dependency.data,
     length
   }
 }

test/snapshots.js

@@ -147,3 +147,36 @@ test('snapshots are consistent', async function (t) {
 
   await snapshot.close()
 })
+
+test('snapshot over named batch persists after truncate', async function (t) {
+  t.plan(8)
+
+  const core = await create(t)
+
+  await core.append('block #0.0')
+  await core.append('block #1.0')
+  await core.append('block #2.0')
+
+  const session = core.session({ name: 'session' })
+  const snapshot = session.snapshot({ valueEncoding: 'utf-8' })
+
+  t.is(snapshot.length, 3)
+
+  t.is(await snapshot.get(1), 'block #1.0')
+
+  await core.truncate(1)
+  await core.append('block #1.1')
+
+  t.is(core.fork, 1, 'clone updated')
+  t.is(core.length, 2, 'core updated')
+
+  // t.is(snapshot.fork, 0, 'snapshot remains')
+  t.is(snapshot.length, 3, 'snapshot remains')
+
+  t.is(await snapshot.get(0), 'block #0.0')
+  t.is(await snapshot.get(1), 'block #1.0')
+  t.is(await snapshot.get(2), 'block #2.0')
+
+  await core.close()
+  await snapshot.close()
+})