Re-scan log into memory after compacting

lib/index.js

@@ -192,7 +192,7 @@ function initDB(peer, config) {
   /** @type {Array<Rec | null>} */
   const recs = []
   /** @type {WeakMap<Rec, Misc>} */
-  const miscRegistry = new WeakMap()
+  let miscRegistry = new WeakMap()
   /** @type {Map<MsgID, Doneable<RecPresent>>} */
   const msgsBeingAdded = new Map()
   /** @type {Map<string, EncryptionFormat>} */
@@ -272,6 +272,34 @@ function initDB(peer, config) {
     )
   })
 
+  /**
+   * @param {CB<void>} cb
+   */
+  function rescanLogPostCompaction(cb) {
+    miscRegistry = new WeakMap()
+    let seq = -1
+    log.scan(
+      function rescanEach(offset, recInLog, size) {
+        seq += 1
+        if (!recInLog) {
+          // deleted record
+          recs[seq] = null
+          return
+        }
+        const rec = decrypt(recInLog, peer, config)
+        miscRegistry.set(rec, { offset, size, seq })
+        recs[seq] = rec
+      },
+      function rescanEnd(err) {
+        // prettier-ignore
+        if (err) return cb(new Error('Failed to rescan the log after compaction', { cause: err }))
+        recs.length = seq + 1
+        cb()
+      },
+      false // asRaw
+    )
+  }
+
   /**
    * @param {MsgID} id
    * @param {Msg} msg
@@ -1183,6 +1211,23 @@ function initDB(peer, config) {
     }
   }
 
+  /** @type {CB<void>} */
+  function logError(err) {
+    if (err) console.error(err)
+  }
+
+  /**
+   * @param {CB<void>} cb
+   */
+  function compact(cb) {
+    cb ??= logError
+    log.compact((err) => {
+      // prettier-ignore
+      if (err) return cb?.(err)
+      rescanLogPostCompaction(cb)
+    });
+  }
+
   return {
     // public
     installEncryptionFormat,
@@ -1217,7 +1262,7 @@ function initDB(peer, config) {
     records,
     log: {
       stats: log.stats.bind(log),
-      compact: log.compact.bind(log),
+      compact,
     },
 
     // internal

lib/log/index.js

@@ -398,6 +398,7 @@ function Log(filename, opts) {
   /**
    * @param {(offset: number, data: extractCodecType<typeof codec> | null, size: number) => Promise<void> | void} onNext
    * @param {(error?: Error) => void} onDone
+   * @param {boolean} asRaw
    */
   function scan(onNext, onDone, asRaw = false) {
     let cursor = 0

test/del.test.js

@@ -34,19 +34,20 @@ test('del()', async (t) => {
     msgIDs.push(rec.id)
   }
 
-  const before = []
-  for (const msg of peer.db.msgs()) {
-    if (msg.data && msg.metadata.account?.length > 4) {
-      before.push(msg.data.text)
+  {
+    const texts = []
+    for (const msg of peer.db.msgs()) {
+      if (msg.data && msg.metadata.account?.length > 4) {
+        texts.push(msg.data.text)
+      }
     }
+    assert.deepEqual(
+      texts,
+      ['m0', 'm1', 'm2', 'm3', 'm4'],
+      'msgs before the delete'
+    )
   }
 
-  assert.deepEqual(
-    before,
-    ['m0', 'm1', 'm2', 'm3', 'm4'],
-    'msgs before the delete'
-  )
-
   const stats1 = await p(peer.db.log.stats)()
   assert.deepEqual(
     stats1,
@@ -55,19 +56,32 @@ test('del()', async (t) => {
   )
 
   await p(peer.db.del)(msgIDs[2])
+  await p(peer.db.del)(msgIDs[3])
 
-  const after = []
-  for (const msg of peer.db.msgs()) {
-    if (msg.data && msg.metadata.account?.length > 4) {
-      after.push(msg.data.text)
+  {
+    const texts = []
+    for (const msg of peer.db.msgs()) {
+      if (msg.data && msg.metadata.account?.length > 4) {
+        texts.push(msg.data.text)
+      }
     }
+    assert.deepEqual(texts, ['m0', 'm1', 'm4'], 'msgs after the delete')
   }
 
-  assert.deepEqual(after, ['m0', 'm1', 'm3', 'm4'], 'msgs after the delete')
-
   await p(peer.db.log.compact)()
   assert('compacted')
 
+  await p(peer.db.del)(msgIDs[4])
+
+  {
+    const texts = []
+    for (const msg of peer.db.msgs()) {
+      if (msg.data && msg.metadata.account?.length > 4) {
+        texts.push(msg.data.text)
+      }
+    }
+    assert.deepEqual(texts, ['m0', 'm1'], 'msgs when deleted after compacted')
+  }
   await p(peer.close)(true)
 
   const log = Log(path.join(DIR, 'db', 'log'), {
@@ -101,7 +115,7 @@ test('del()', async (t) => {
   const stats2 = await p(log.stats)()
   assert.deepEqual(
     stats2,
-    { totalBytes: 3495, deletedBytes: 0 },
+    { totalBytes: 2880, deletedBytes: 615 },
     'stats after delete and compact'
   )
 
@@ -109,7 +123,7 @@ test('del()', async (t) => {
     persistedMsgs
       .filter((msg) => msg.data && msg.metadata.account?.length > 4)
       .map((msg) => msg.data.text),
-    ['m0', 'm1', 'm3', 'm4'],
+    ['m0', 'm1'],
     'msgs in disk after the delete'
   )
 })