feat: store playlists with a fixed favorites list for every account

db/migrations/00004_playlists.sql

@@ -0,0 +1,35 @@
+-- +goose Up
+CREATE TABLE playlists (
+    id uuid PRIMARY KEY DEFAULT uuidv7(),
+    owner_id uuid NOT NULL REFERENCES members ON DELETE CASCADE,
+    -- 每个账号恰好一个“我喜欢”：注册时创建，不能改名或删除。
+    kind text NOT NULL CHECK (kind IN ('favorites', 'custom')),
+    name text NOT NULL,
+    -- 新加入的曲目取 item_seq + 1 作为排序值，排在最前。
+    item_seq bigint NOT NULL DEFAULT 0,
+    created_at timestamptz NOT NULL DEFAULT now(),
+    -- 歌单改名或曲目增减的时间。
+    updated_at timestamptz NOT NULL DEFAULT now()
+);
+
+CREATE INDEX ON playlists (owner_id);
+CREATE UNIQUE INDEX ON playlists (owner_id) WHERE kind = 'favorites';
+
+-- 展示用的元数据存一份快照：歌单里的歌不一定准备过，tracks 表里可能没有。
+CREATE TABLE playlist_items (
+    playlist_id uuid NOT NULL REFERENCES playlists ON DELETE CASCADE,
+    source text NOT NULL,
+    track_id text NOT NULL,
+    title text NOT NULL,
+    artist text,
+    album text,
+    cover_url text,
+    cover_key text,
+    duration_ms bigint NOT NULL,
+    page_url text NOT NULL,
+    position bigint NOT NULL,
+    added_at timestamptz NOT NULL DEFAULT now(),
+    PRIMARY KEY (playlist_id, source, track_id)
+);
+
+CREATE INDEX ON playlist_items (playlist_id, position DESC);

db/queries/playlists.sql

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+-- name: CreateFavorites :exec
+INSERT INTO playlists (owner_id, kind, name) VALUES (@owner_id, 'favorites', '我喜欢');
+
+-- name: MemberPlaylists :many
+SELECT p.id, p.kind, p.name, p.created_at, p.updated_at, count(i.track_id)::bigint AS track_count
+FROM playlists p
+LEFT JOIN playlist_items i ON i.playlist_id = p.id
+WHERE p.owner_id = @owner_id
+GROUP BY p.id
+ORDER BY p.kind = 'favorites' DESC, p.created_at, p.id;
+
+-- name: MemberPlaylistCovers :many
+SELECT DISTINCT ON (i.playlist_id) i.playlist_id, i.cover_url, i.cover_key
+FROM playlist_items i
+JOIN playlists p ON p.id = i.playlist_id
+WHERE p.owner_id = @owner_id AND (i.cover_url IS NOT NULL OR i.cover_key IS NOT NULL)
+ORDER BY i.playlist_id, i.position DESC;
+
+-- name: LockFavorites :exec
+-- 新建歌单前锁住这个账号的“我喜欢”：同一个账号并发新建时依次计数，不会越过上限。
+SELECT id FROM playlists WHERE owner_id = @owner_id AND kind = 'favorites' FOR UPDATE;
+
+-- name: CountPlaylists :one
+SELECT count(*) FROM playlists WHERE owner_id = @owner_id;
+
+-- name: CreatePlaylist :one
+INSERT INTO playlists (owner_id, kind, name) VALUES (@owner_id, 'custom', @name)
+RETURNING id, created_at, updated_at;
+
+-- name: PlaylistKind :one
+SELECT kind FROM playlists WHERE id = @id AND owner_id = @owner_id;
+
+-- name: RenamePlaylist :execrows
+UPDATE playlists SET name = @name, updated_at = now() WHERE id = @id AND owner_id = @owner_id AND kind = 'custom';
+
+-- name: DeletePlaylist :execrows
+DELETE FROM playlists WHERE id = @id AND owner_id = @owner_id AND kind = 'custom';
+
+-- name: LockPlaylist :one
+-- 改动曲目前锁住歌单：并发加入时依次检查上限、分配排序值。删除歌单先锁歌单行再级联删除曲目，其他操作也要先锁歌单再动曲目，否则会互相死锁。
+SELECT item_seq FROM playlists WHERE id = @id AND owner_id = @owner_id FOR UPDATE;
+
+-- name: PlaylistHasItem :one
+SELECT EXISTS (SELECT FROM playlist_items WHERE playlist_id = @playlist_id AND source = @source AND track_id = @track_id);
+
+-- name: CountPlaylistItems :one
+SELECT count(*) FROM playlist_items WHERE playlist_id = @playlist_id;
+
+-- name: InsertPlaylistItem :exec
+INSERT INTO playlist_items (playlist_id, source, track_id, title, artist, album, cover_url, cover_key, duration_ms, page_url, position)
+VALUES (@playlist_id, @source, @track_id, @title, @artist, @album, @cover_url, @cover_key, @duration_ms, @page_url, @position);
+
+-- name: SetPlaylistSeq :exec
+UPDATE playlists SET item_seq = @item_seq, updated_at = now() WHERE id = @id;
+
+-- name: PlaylistItems :many
+SELECT * FROM playlist_items WHERE playlist_id = @playlist_id ORDER BY position DESC;
+
+-- name: DeletePlaylistItem :exec
+WITH deleted AS (
+    DELETE FROM playlist_items WHERE playlist_id = @playlist_id AND source = @source AND track_id = @track_id
+    RETURNING playlist_id
+)
+UPDATE playlists SET updated_at = now() WHERE id IN (SELECT playlist_id FROM deleted);