Documents are split into chunks before hitting the database, so there is no need to reconstruct trees in PostgreSQL. Indeed, many queries don't need to reconstruct the (whole) tree, just a part of it or even just one level. However, in doing so, ToroDB is able to offer queries that only need so scan a small subset of the database (compared to the whole database) to query your data.
ToroDB was inspired by the DRY principle: relational databases like PostgreSQL are already good enough that with some tweaking may perfectly well as a document-store.
Documents are split into chunks before hitting the database, so there is no need to reconstruct trees in PostgreSQL. Indeed, many queries don't need to reconstruct the (whole) tree, just a part of it or even just one level. However, in doing so, ToroDB is able to offer queries that only need so scan a small subset of the database (compared to the whole database) to query your data.
ToroDB was inspired by the DRY principle: relational databases like PostgreSQL are already good enough that with some tweaking may perfectly well as a document-store.