Read the library's last read time without joining history to chapters

Migration 18 replaces libraryView, so the version code is bumped.

app/build.gradle.kts

@@ -37,7 +37,7 @@ android {
     defaultConfig {
         applicationId = "app.mihon"
 
-        versionCode = 34
+        versionCode = 35
         versionName = "0.20.4"
 
         buildConfigField("boolean", "TELEMETRY_INCLUDED", "${Config.includeTelemetry}")

data/src/main/sqldelight/tachiyomi/migrations/18.sqm

@@ -0,0 +1,59 @@
+-- Read the library's last read time from history without joining it to every chapter
+
+DROP VIEW libraryView;
+
+CREATE VIEW libraryView AS
+SELECT
+    M.*,
+    coalesce(C.total, 0) AS totalCount,
+    coalesce(C.readCount, 0) AS readCount,
+    coalesce(C.latestUpload, 0) AS latestUpload,
+    coalesce(C.fetchedAt, 0) AS chapterFetchedAt,
+    -- Joining history to every chapter is the slowest part of the query, and only entries with excluded
+    -- scanlators need the chapters to leave theirs out
+    coalesce(
+        CASE WHEN EXISTS (SELECT 0 FROM excluded_scanlator WHERE excluded_scanlator.manga_id = M.id)
+        THEN (
+            SELECT max(history.read_at)
+            FROM history
+            JOIN chapter
+            ON chapter.id = history.chapter_id
+            WHERE history.manga_id = M.id
+            AND NOT EXISTS (
+                SELECT 0 FROM excluded_scanlator
+                WHERE excluded_scanlator.manga_id = M.id
+                AND excluded_scanlator.scanlator = chapter.remote_scanlator
+            )
+        )
+        ELSE (SELECT max(history.read_at) FROM history WHERE history.manga_id = M.id)
+        END,
+        0
+    ) AS lastRead,
+    coalesce(C.bookmarkCount, 0) AS bookmarkCount,
+    coalesce(MC.categories, '0') AS categories
+FROM manga M
+LEFT JOIN (
+    SELECT
+        chapter.manga_id,
+        count(*) AS total,
+        sum(user_read) AS readCount,
+        coalesce(max(chapter.remote_date_upload), 0) AS latestUpload,
+        coalesce(max(chapter.state_date_fetch), 0) AS fetchedAt,
+        sum(chapter.user_bookmark) AS bookmarkCount
+    FROM chapter
+    LEFT JOIN excluded_scanlator
+    ON chapter.manga_id = excluded_scanlator.manga_id
+    AND chapter.remote_scanlator = excluded_scanlator.scanlator
+    WHERE excluded_scanlator.scanlator IS NULL
+    AND chapter.manga_id IN (SELECT id FROM manga WHERE user_favorite_at IS NOT NULL)
+    GROUP BY chapter.manga_id
+) AS C
+ON M.id = C.manga_id
+LEFT JOIN (
+    SELECT manga_id, group_concat(category_id) AS categories
+    FROM manga_category
+    WHERE manga_id IN (SELECT id FROM manga WHERE user_favorite_at IS NOT NULL)
+    GROUP BY manga_id
+) AS MC
+ON MC.manga_id = M.id
+WHERE M.user_favorite_at IS NOT NULL;

data/src/main/sqldelight/tachiyomi/view/libraryView.sq

@@ -5,7 +5,26 @@ SELECT
     coalesce(C.readCount, 0) AS readCount,
     coalesce(C.latestUpload, 0) AS latestUpload,
     coalesce(C.fetchedAt, 0) AS chapterFetchedAt,
-    coalesce(C.lastRead, 0) AS lastRead,
+    -- Joining history to every chapter is the slowest part of the query, and only entries with excluded
+    -- scanlators need the chapters to leave theirs out
+    coalesce(
+        CASE WHEN EXISTS (SELECT 0 FROM excluded_scanlator WHERE excluded_scanlator.manga_id = M.id)
+        THEN (
+            SELECT max(history.read_at)
+            FROM history
+            JOIN chapter
+            ON chapter.id = history.chapter_id
+            WHERE history.manga_id = M.id
+            AND NOT EXISTS (
+                SELECT 0 FROM excluded_scanlator
+                WHERE excluded_scanlator.manga_id = M.id
+                AND excluded_scanlator.scanlator = chapter.remote_scanlator
+            )
+        )
+        ELSE (SELECT max(history.read_at) FROM history WHERE history.manga_id = M.id)
+        END,
+        0
+    ) AS lastRead,
     coalesce(C.bookmarkCount, 0) AS bookmarkCount,
     coalesce(MC.categories, '0') AS categories
 FROM manga M
@@ -15,15 +34,12 @@ LEFT JOIN (
         count(*) AS total,
         sum(user_read) AS readCount,
         coalesce(max(chapter.remote_date_upload), 0) AS latestUpload,
-        coalesce(max(history.read_at), 0) AS lastRead,
         coalesce(max(chapter.state_date_fetch), 0) AS fetchedAt,
         sum(chapter.user_bookmark) AS bookmarkCount
     FROM chapter
     LEFT JOIN excluded_scanlator
     ON chapter.manga_id = excluded_scanlator.manga_id
     AND chapter.remote_scanlator = excluded_scanlator.scanlator
-    LEFT JOIN history
-    ON chapter.id = history.chapter_id
     WHERE excluded_scanlator.scanlator IS NULL
     AND chapter.manga_id IN (SELECT id FROM manga WHERE user_favorite_at IS NOT NULL)
     GROUP BY chapter.manga_id