This is generally true, but there are some additional aspects.
1. With PostgreSQL heap, you need to access the heap page itself. And it's not for free. It goes all through the buffer manager and other related components.
According to all of the above, I believe OrioleDB still wins in the case of secondary key lookup. I think this is indirectly confirmed by the results of the TPC-C benchmark, which contains quite a lot of log of secondary key lookups. However, this subject is worth dedicated benchmarking in the future.
1. With PostgreSQL heap, you need to access the heap page itself. And it's not for free. It goes all through the buffer manager and other related components.
2. In OrioleDB, we have a lightweight protocol to read from pages. In-memory pages are connected using direct links (https://www.orioledb.com/docs/architecture/overview#dual-poi...), and pages are read lock-less (https://www.orioledb.com/docs/architecture/overview#page-str...). Additionally, tree navigation for simple data types skips both copying and tuple deforming (https://www.orioledb.com/blog/orioledb-fastpath-search).
According to all of the above, I believe OrioleDB still wins in the case of secondary key lookup. I think this is indirectly confirmed by the results of the TPC-C benchmark, which contains quite a lot of log of secondary key lookups. However, this subject is worth dedicated benchmarking in the future.