Batch database operations during backup restore for improved performance (#3267)

* perf(backup): batch database operations during restore

Reduce overhead by chunking manga and repo restoration into
transactions of 100 entries. Categories now restored in a single
transaction. Optimized DatabaseHandler to reuse existing transaction
contexts instead of creating redundant nested ones.

Changed TransactionElement to internal to allow AndroidDatabaseHandler
to check transaction state from the same package.

* fix(backup): make restore progress and errors thread-safe

Use AtomicInteger for progress and synchronizedList for errors to
prevent race conditions during concurrent restoration coroutines.

* perf(backup): update progress notification only once per chunk

Reduce UI/IPC overhead by moving notification updates out of the inner
loop, triggering them only after each 100-item transaction chunk.

Reduced on my emulator from 46 seconds to 27

* fix: remove invalid awaitAsOne() call on insert() return type

categoriesQueries.insert() returns Long (the inserted row ID), not an
ExecutableQuery<T>, so awaitAsOne() is not applicable.

* fix(feedback): Use `CopyOnWriteArrayList` and kotlin `AtomicInt`, add a changelog entry

Note that using kotlin `AtomicInt` instead of java `AtomicInteger` requires opting into an experimental API.

---------

Co-authored-by: AntsyLich <59261191+AntsyLich@users.noreply.github.com>

CHANGELOG.md

@@ -20,6 +20,9 @@ The format is a modified version of [Keep a Changelog](https://keepachangelog.co
 - Change the term "Obsolete" to "Orphaned" for extensions ([@AntsyLich](https://github.com/AntsyLich)) ([#3383](https://github.com/mihonapp/mihon/pull/3383))
 - Remove text limit of manga notes ([@AntsyLich](https://github.com/AntsyLich)) ([#3410](https://github.com/mihonapp/mihon/pull/3410))
 
+### Improved
+- Batch database operations during backup restore for improved performance ([@Lolle2000la](https://github.com/Lolle2000la)) ([#3267](https://github.com/mihonapp/mihon/pull/3267))
+
 ### Fixed
 - Add missing `outlineVariant` color to Nord theme ([@CompileConnected](https://github.com/CompileConnected)) ([#3184](https://github.com/mihonapp/mihon/pull/3184))
 - Continue reading button missing when unread filter is off ([@AntsyLich](https://github.com/AntsyLich)) ([#3382](https://github.com/mihonapp/mihon/pull/3382))

app/src/main/java/eu/kanade/tachiyomi/data/backup/restore/BackupRestorer.kt

@@ -19,17 +19,26 @@ import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.ensureActive
 import kotlinx.coroutines.launch
 import tachiyomi.core.common.i18n.stringResource
+import tachiyomi.data.Database
 import tachiyomi.i18n.MR
+import uy.kohesive.injekt.Injekt
+import uy.kohesive.injekt.api.get
 import java.io.File
 import java.text.SimpleDateFormat
 import java.util.Date
 import java.util.Locale
+import java.util.concurrent.CopyOnWriteArrayList
+import kotlin.concurrent.atomics.AtomicInt
+import kotlin.concurrent.atomics.ExperimentalAtomicApi
+import kotlin.concurrent.atomics.incrementAndFetch
 
+@OptIn(ExperimentalAtomicApi::class)
 class BackupRestorer(
     private val context: Context,
     private val notifier: BackupNotifier,
     private val isSync: Boolean,
 
+    private val database: Database = Injekt.get(),
     private val categoriesRestorer: CategoriesRestorer = CategoriesRestorer(),
     private val preferenceRestorer: PreferenceRestorer = PreferenceRestorer(context),
     private val extensionStoreRestorer: ExtensionStoreRestorer = ExtensionStoreRestorer(),
@@ -37,8 +46,8 @@ class BackupRestorer(
 ) {
 
     private var restoreAmount = 0
-    private var restoreProgress = 0
-    private val errors = mutableListOf<Pair<Date, String>>()
+    private val restoreProgress = AtomicInt(0)
+    private val errors = CopyOnWriteArrayList<Pair<Date, String>>()
 
     /**
      * Mapping of source ID to source name from backup data
@@ -111,10 +120,10 @@ class BackupRestorer(
         ensureActive()
         categoriesRestorer(backupCategories)
 
-        restoreProgress += 1
+        val progress = restoreProgress.incrementAndFetch()
         notifier.showRestoreProgress(
             context.stringResource(MR.strings.categories),
-            restoreProgress,
+            progress,
             restoreAmount,
             isSync,
         )
@@ -125,7 +134,10 @@ class BackupRestorer(
         backupCategories: List<BackupCategory>,
     ) = launch {
         mangaRestorer.sortByNew(backupMangas)
-            .forEach {
+            .chunked(100)
+            .forEach { chunk ->
+                database.transaction {
+                    chunk.forEach {
                         ensureActive()
 
                         try {
@@ -135,8 +147,10 @@ class BackupRestorer(
                             errors.add(Date() to "${it.title} [$sourceName]: ${e.message}")
                         }
 
-                restoreProgress += 1
-                notifier.showRestoreProgress(it.title, restoreProgress, restoreAmount, isSync)
+                        restoreProgress.incrementAndFetch()
+                    }
+                }
+                notifier.showRestoreProgress(chunk.last().title, restoreProgress.load(), restoreAmount, isSync)
             }
     }
 
@@ -150,10 +164,10 @@ class BackupRestorer(
             categories,
         )
 
-        restoreProgress += 1
+        val progress = restoreProgress.incrementAndFetch()
         notifier.showRestoreProgress(
             context.stringResource(MR.strings.app_settings),
-            restoreProgress,
+            progress,
             restoreAmount,
             isSync,
         )
@@ -163,10 +177,10 @@ class BackupRestorer(
         ensureActive()
         preferenceRestorer.restoreSource(preferences)
 
-        restoreProgress += 1
+        val progress = restoreProgress.incrementAndFetch()
         notifier.showRestoreProgress(
             context.stringResource(MR.strings.source_settings),
-            restoreProgress,
+            progress,
             restoreAmount,
             isSync,
         )
@@ -176,7 +190,10 @@ class BackupRestorer(
         backupExtensionStores: List<BackupExtensionStore>,
     ) = launch {
         backupExtensionStores
-            .forEach {
+            .chunked(100)
+            .forEach { chunk ->
+                database.transaction {
+                    chunk.forEach {
                         ensureActive()
 
                         try {
@@ -185,10 +202,12 @@ class BackupRestorer(
                             errors.add(Date() to "Error Adding Repo: ${it.name} : ${e.message}")
                         }
 
-                restoreProgress += 1
+                        restoreProgress.incrementAndFetch()
+                    }
+                }
                 notifier.showRestoreProgress(
                     context.stringResource(MR.strings.extensionStores),
-                    restoreProgress,
+                    restoreProgress.load(),
                     restoreAmount,
                     isSync,
                 )
@@ -208,7 +227,7 @@ class BackupRestorer(
                 }
                 return file
             }
-        } catch (e: Exception) {
+        } catch (_: Exception) {
             // Empty
         }
         return File("")

app/src/main/java/eu/kanade/tachiyomi/data/backup/restore/restorers/CategoriesRestorer.kt

@@ -19,7 +19,8 @@ class CategoriesRestorer(
             val dbCategoriesByName = dbCategories.associateBy { it.name }
             var nextOrder = dbCategories.maxOfOrNull { it.order }?.plus(1) ?: 0
 
-            val categories = backupCategories
+            val categories = database.transactionWithResult {
+                backupCategories
                     .sortedBy { it.order }
                     .map {
                         val dbCategory = dbCategoriesByName[it.name]
@@ -29,6 +30,7 @@ class CategoriesRestorer(
                             .insert(it.name, order, it.flags)
                             .let { id -> it.toCategory(id).copy(order = order) }
                     }
+            }
 
             libraryPreferences.categorizedDisplaySettings.set(
                 (dbCategories + categories)