perf(podcast): cache subscription load + batch feed property reads

The detail screen reloaded the full subscription list from the database on every open, and list_podcast_documents read each feed property with its own SQLite connection. Both are redundant work on a hot path. Add PodcastRepository.ensurePodcastsLoaded() (load-once, with subscribe/ unsubscribe still forcing a refresh) and use it from the detail and library screens instead of reloading unconditionally. Batch list_podcast_documents' property reads through list_properties_for_documents (~2 connection opens instead of ~5 per feed). Verified on emulator: opening the detail screen twice triggers the database load only once, with no network access on cached opens. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-03 01:20:49 -07:00
parent 43434a1a21
commit a14cb53923
4 changed files with 51 additions and 34 deletions
@@ -28,6 +28,16 @@ class PodcastRepository(private val nativeLib: NativeLib) {

    private val tag = "PodcastRepository"

+    // Set once the subscription map has been successfully loaded from the database. Mutations
+    // (subscribe/unsubscribe) refresh via loadPodcastsFromDatabase(), so callers that only need the
+    // current subscription state can use ensurePodcastsLoaded() to avoid redundant reloads.
+    @Volatile private var podcastsLoaded = false
+
+    /** Load the subscription map from disk only if it hasn't been loaded yet. */
+    suspend fun ensurePodcastsLoaded() {
+        if (!podcastsLoaded) loadPodcastsFromDatabase()
+    }
+
    suspend fun loadPodcastsFromDatabase() =
        withContext(Dispatchers.IO) {
            Log.d(tag, "Loading podcasts from native database")
@@ -44,6 +54,7 @@ class PodcastRepository(private val nativeLib: NativeLib) {
            Log.d(tag, "Converted ${podcastMap.size} items to podcasts")
            _subscribedPodcasts.value = podcastMap
            _podcasts.value = _podcasts.value + podcastMap
+            podcastsLoaded = true
        }

    private fun convertItemToPodcast(item: PodcastItem): Podcast? {
@@ -66,7 +66,7 @@ fun PodcastDetailScreen(
        episodesError = null
        allLoaded = false
        try {
-            podcastRepository.loadPodcastsFromDatabase()
+            podcastRepository.ensurePodcastsLoaded()
            val docId = podcastRepository.subscribedFeedDocumentId(podcast.id)
            feedDocId = docId

@@ -129,10 +129,7 @@ fun PodcastDetailScreen(
    ) {
        Column(modifier = Modifier.fillMaxSize()) {
            // Back button row
-            Row(
-                modifier = Modifier.fillMaxWidth(),
-                horizontalArrangement = Arrangement.End,
-            ) {
+            Row(modifier = Modifier.fillMaxWidth(), horizontalArrangement = Arrangement.End) {
                BackButton(onClick = onBack)
            }

@@ -31,7 +31,7 @@ fun PodcastLibraryScreen(
    // Load podcasts from repository when the screen is first displayed
    val podcasts by podcastRepository.subscribedPodcasts.collectAsState()

-    LaunchedEffect(Unit) { podcastRepository.loadPodcastsFromDatabase() }
+    LaunchedEffect(Unit) { podcastRepository.ensurePodcastsLoaded() }

    var selectedMode by remember { mutableStateOf(PodcastLibraryMode.Subscriptions) }

@@ -1538,36 +1538,45 @@ impl SyncNode {

    pub fn list_podcast_documents(&self) -> Result<Vec<PodcastItem>, SyncError> {
        self.with_store(|store| {
-            store
-                .doc_store
-                .list_documents_by_type(&DocumentType::PodcastFeed)?
-                .iter()
+            let feed_docs = store.doc_store.list_documents_by_type(&DocumentType::PodcastFeed)?;
+
+            // One batched query for every feed's properties rather than a SQLite
+            // connection per property read.
+            let ids: Vec<DocumentID> = feed_docs.iter().map(|doc| doc.id.clone()).collect();
+            let props_by_doc = store.doc_store.list_properties_for_documents(&ids)?;
+
+            let items = feed_docs
+                .into_iter()
                .map(|doc| {
-                    let id = &doc.id;
-                    let cover =
-                        get_text_prop(&store.doc_store, id, &PropertyKind::PodcastFeedCoverArtUrl);
-                    Ok(PodcastItem {
-                        id: id.to_string(),
-                        podcast_api_id: get_text_prop(
-                            &store.doc_store,
-                            id,
-                            &PropertyKind::PodcastFeedRssUrl,
-                        ),
-                        title: get_text_prop(&store.doc_store, id, &PropertyKind::PodcastFeedTitle),
-                        description: get_text_prop(
-                            &store.doc_store,
-                            id,
-                            &PropertyKind::PodcastFeedDescription,
-                        ),
-                        author: get_text_prop(
-                            &store.doc_store,
-                            id,
-                            &PropertyKind::PodcastFeedAuthor,
-                        ),
-                        cover_art_url: if cover.is_empty() { None } else { Some(cover) },
-                    })
+                    let mut item = PodcastItem {
+                        id: doc.id.to_string(),
+                        podcast_api_id: String::new(),
+                        title: String::new(),
+                        description: String::new(),
+                        author: String::new(),
+                        cover_art_url: None,
+                    };
+                    if let Some(props) = props_by_doc.get(&doc.id) {
+                        for p in props {
+                            let PropertyValue::Text(s) = &p.value else { continue };
+                            match p.kind {
+                                PropertyKind::PodcastFeedRssUrl => item.podcast_api_id = s.clone(),
+                                PropertyKind::PodcastFeedTitle => item.title = s.clone(),
+                                PropertyKind::PodcastFeedDescription => {
+                                    item.description = s.clone()
+                                }
+                                PropertyKind::PodcastFeedAuthor => item.author = s.clone(),
+                                PropertyKind::PodcastFeedCoverArtUrl if !s.is_empty() => {
+                                    item.cover_art_url = Some(s.clone())
+                                }
+                                _ => {}
+                            }
+                        }
+                    }
+                    item
                })
-                .collect()
+                .collect();
+            Ok(items)
        })
    }