batched profile / 20 books, 5 distinct authors (4 books per author) — one batched IN query

1. select b1_0.id,b1_0.author_id,b1_0.title from book b1_0
2. select a1_0.id,a1_0.name from author a1_0 where a1_0.id in (?,?,?,?,?)

total statements: 2
