优化

internal/database/schema_migration.go

@@ -8,6 +8,11 @@ import (
 
 // AutoMigrate creates tables for every model registered in the model package.
 func AutoMigrate(db *gorm.DB) error {
+	// 必须先于 AutoMigrate：旧库中可能已有重复的 (user_id, media_id) 历史行，
+	// 不去重会导致唯一索引 uniq_user_history 创建失败。
+	if err := dedupePlaybackHistories(db); err != nil {
+		return err
+	}
 	if err := db.AutoMigrate(model.AllModels()...); err != nil {
 		return err
 	}
@@ -37,6 +42,27 @@ func ensureSQLiteQueryOptimizer(db *gorm.DB) error {
 	return db.Exec("ANALYZE").Error
 }
 
+// dedupePlaybackHistories removes duplicate (user_id, media_id) rows left by
+// the former read-then-write upsert, so the uniq_user_history composite unique
+// index can be created on existing databases. Keeps the most recent row per
+// pair, preferring live rows over soft-deleted ones.
+func dedupePlaybackHistories(db *gorm.DB) error {
+	if !db.Migrator().HasTable("playback_histories") {
+		return nil
+	}
+	return db.Exec(`
+DELETE FROM playback_histories WHERE id IN (
+	SELECT id FROM (
+		SELECT id, ROW_NUMBER() OVER (
+			PARTITION BY user_id, media_id
+			ORDER BY deleted_at IS NULL DESC, watched_at DESC, id DESC
+		) AS rn
+		FROM playback_histories
+	) ranked
+	WHERE ranked.rn > 1
+)`).Error
+}
+
 func ensurePostgresColumnCompatibility(db *gorm.DB) error {
 	if !isPostgres(db) {
 		return nil

internal/database/schema_migration_history_test.go

@@ -0,0 +1,84 @@
+package database
+
+import (
+	"testing"
+	"time"
+
+	"github.com/glebarez/sqlite"
+	"gorm.io/gorm"
+)
+
+// TestAutoMigrateDedupesPlaybackHistories reproduces the upgrade path: a legacy
+// database contains duplicate (user_id, media_id) history rows created by the
+// old read-then-write upsert. AutoMigrate must merge them before creating the
+// uniq_user_history composite unique index, otherwise the upgrade fails.
+func TestAutoMigrateDedupesPlaybackHistories(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	// 旧 schema：无 uniq_user_history 唯一索引。
+	if err := db.Exec(`CREATE TABLE playback_histories (
+		id varchar(36) PRIMARY KEY,
+		created_at datetime,
+		updated_at datetime,
+		deleted_at datetime,
+		user_id varchar(36) NOT NULL,
+		media_id varchar(128) NOT NULL,
+		position_ms integer,
+		duration_ms integer,
+		watched_at datetime,
+		completed numeric
+	)`).Error; err != nil {
+		t.Fatal(err)
+	}
+	base := time.Now()
+	rows := []struct {
+		id        string
+		position  int64
+		watchedAt time.Time
+	}{
+		{"h-old", 1_000, base.Add(-2 * time.Hour)},
+		{"h-mid", 2_000, base.Add(-1 * time.Hour)},
+		{"h-new", 3_000, base},
+	}
+	for _, r := range rows {
+		if err := db.Exec(
+			`INSERT INTO playback_histories (id, user_id, media_id, position_ms, watched_at, created_at, updated_at)
+			 VALUES (?, 'u-1', 'm-1', ?, ?, ?, ?)`,
+			r.id, r.position, r.watchedAt, r.watchedAt, r.watchedAt,
+		).Error; err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	if err := AutoMigrate(db); err != nil {
+		t.Fatalf("auto migrate with duplicate histories: %v", err)
+	}
+
+	var count int64
+	if err := db.Table("playback_histories").Where("user_id = ? AND media_id = ?", "u-1", "m-1").Count(&count).Error; err != nil {
+		t.Fatal(err)
+	}
+	if count != 1 {
+		t.Fatalf("expected duplicate rows merged to 1, got %d", count)
+	}
+	var position int64
+	if err := db.Table("playback_histories").
+		Where("user_id = ? AND media_id = ?", "u-1", "m-1").
+		Select("position_ms").Scan(&position).Error; err != nil {
+		t.Fatal(err)
+	}
+	if position != 3_000 {
+		t.Fatalf("dedupe should keep the most recent row, got position_ms=%d", position)
+	}
+
+	// 唯一索引存在时，重复插入同一 (user_id, media_id) 应触发冲突而非新增行。
+	if err := db.Exec(
+		`INSERT INTO playback_histories (id, user_id, media_id, position_ms, watched_at, created_at, updated_at)
+		 VALUES ('h-dup', 'u-1', 'm-1', 4_000, ?, ?, ?)`,
+		base, base, base,
+	).Error; err == nil {
+		t.Fatal("insert violating uniq_user_history should fail")
+	}
+}