Postgrest is more like a compiler, it takes one language as input (REST) and outputs another language (SQL) as output.
It has 0 relation to the ORM concept
Postgrest is not an ORM, it just takes rows from your database and sends them to the client.
It encourages you to write SQL. Write a decent SQL schema. Write SQL views on top of that schema to provide the rows to your API. Even write SQL functions to modify the data in reaction to client calls!
If you hate ORMs and love SQL (specially Postgres, because it's amazing) this is the tool you should be using.
My point is - exposing db over HTTP (REST, GraphQL, ...) is bad architectural design and idea.
You say "expose db" and imply that one would directly give access to the core tables and in this way coupling the api to the data model (one should expose only views and stored procedures) and making the api inflexible.
Or are you saying this is insecure, and if so, can you describe how one would "break" this?
I'm with you that exposing a fairly free-form query language over HTTP seems like something that's gonna bite several someones in the ass pretty hard at some point (GraphQL) but what's that got to do with PostgREST?
That's why one does not deploy postgrest alone but use it in a setting like this https://github.com/subzerocloud/postgrest-starter-kit
where you at the proxy level can say things like "return 400 if the client did not provide at least 2 filters for the table" or "allow filtering on column a and b because they have indexes but not on c"
But again, those are things to consider when you have datasets exceding hundreds of K or millions, you don't need to care about this when you have tables with 10s of Ks
Exposing a poorly-indexed table can happen in any ol' Rails API app with the usual lazy 3-line controller methods bouncing about its codebase—that's the same level of risk in any system using a database, more or less. I don't see PostgREST as being more likely to cause that to happen. GraphQL's trickier, especially from a performance perspective, because the scope of a query is so hard to determine or account for up-front, and it's hard to confidently answer the question "what's the largest possible scope of a request to this endpoint?".
Also GraphQL is a protocol and you can't really say it will have poor performance, it all depends on the specific implementation of a particular schema. You can have a GraphQL schema where each query gets translated into a single sql query [1] jsut like with postgrest. One thing that is true is that the reference implementation for graphql servers (but only because it has to be general) pushes one in a direction where a single graphql request might generate a storm of sql queries but it's on developer to understand and write proper resolvers.
The whole point of HTTP is CRUD (Create Read Update Delete). PostgREST maps the HTTP Methods POST/GET/PATCH/DELETE to SQL's INSERT/SELECT/UPDATE/DELETE.
The generated SQL statements over HTTP requests are there to help reduce SQL boilerplate but you're expected to write custom views, functions, triggers, constraints, etc and understand "low level" pg.
So they added REST on top of ORM, few more layers of data transformation and even leakier abstraction, so poor dev doesn't have to worry about "low level" SQL.
I lost count of how many different libs/frameworks i saw that exposed CRUD through HTTP, all failed miserably, because it is actually very dumb idea.