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I have a dumb, and likely annoying, question: why isn't Rust the clear choice? I think it has to do with Zig's "interop with C" but this is very abstract for me

I have a dumb, and likely annoying, question: why isn't Rust the clear choice? I think it has to do with Zig's "interop with C" but this is very abstract for me. Is there a code example that shows something that's super easy in Zig but a PITA in Rust? I've heard that Rust's types and compiler can be frustrating to deal with as well. Is Zig a more "joyful" programming language?

minimaxir 3y ago
There is a separate project to build Postgres extensions with Rust: https://github.com/pgcentralfoundation/pgrx https://github.com/pgcentralfoundation/pgrx
- nextaccountic 3y ago
  And lots of interesting extensions use it, like https://github.com/tembo-io/pgmq https://github.com/tembo-io/pgmq https://github.com/zombodb/zombodb https://github.com/zombodb/zombodb https://github.com/supabase/pg_jsonschema https://github.com/supabase/pg_jsonschema
giovannibonetti 3y ago
I've heard that when working with complex data structures with Rust you often need to write unsafe code, which is a lot more painful to work with in Rust. Once in you are in unsafe land anyway, some people say Zig is more convenient.
ccleve 3y ago
I haven't worked with pgzx, but it's possible that memory management is easier. Zig uses memory arenas, and so does Postgres. If one can map directly to the other, it would be a huge win. With Rust/pgrx (which I have used, extensively) memory integration is more difficult. There's pg memory, and there's Rust memory, and they're not the same, and you have to play games to pass data between them. Lifetime issues crop up. Rust might be able to solve the problem in the future with custom allocators, but it's just not there yet.
- bear9628 3y ago
  > I haven't worked with pgzx, but it's possible that memory management is easier. Zig uses memory arenas, and so does Postgres. If one can map directly to the other, it would be a huge win. Yes. This was indeed a great motivator for using Zig. It was quite easy to integrate Zig with the Postgres memory management. This way we can use the Zig standard library or other Zig libraries without a second thought. Another advantage is that in Postgres memory context cleanup and error handling are somewhat well integrated with each other. This gives us some peace of mind as almost any Postgres function you might want to use in your extension is likely to raise an exception.
tudorg 3y ago
It's for sure the question that a lot of people have. Initially we had more details about that in the blog post, but we didn't want it to become a "Zig vs Rust" blog post, so we kept it to a minimum. I will expand just a little bit more here: First, I think the fact that Rust can be a trusted language for Postgres is a huge advantage, and I am excited about it! I hope we will have the chance to use it and contribute to pgrx as well. Postgres is not only written in C, but it has developed its own particular style of C code. For example: arena memory allocator (memory contexts), exceptions via setjmp/longjmp (ereport), single-threaded communicating via shared memory, SPI for accessing the data via SQL, etc. Some of these mechanisms kind of conflict with the way Rust likes to do things. Because of the above, pgrx has to do harder work to expose functionality. It's possible, just a lot of work. In Zig, we can use pretty much anything directly or with small wrappers. If you need to call into C a lot, you need to use unsafe, and that negates some of the memory safety advantages of Rust. Also, Rust unsafe code is harder to write.
weinzierl 3y ago
Here is talk and slides about how to create postgres extensions in Rust. https://rustlab.it/talks/teaching-an-old-dog-new-tricks-extending-postgres-capabilities-with-rust https://rustlab.it/talks/teaching-an-old-dog-new-tricks-exte...

minimaxir 3y ago

There is a separate project to build Postgres extensions with Rust: https://github.com/pgcentralfoundation/pgrx https://github.com/pgcentralfoundation/pgrx

nextaccountic 3y ago
And lots of interesting extensions use it, like https://github.com/tembo-io/pgmq https://github.com/tembo-io/pgmq https://github.com/zombodb/zombodb https://github.com/zombodb/zombodb https://github.com/supabase/pg_jsonschema https://github.com/supabase/pg_jsonschema

giovannibonetti 3y ago

I've heard that when working with complex data structures with Rust you often need to write unsafe code, which is a lot more painful to work with in Rust. Once in you are in unsafe land anyway, some people say Zig is more convenient.

ccleve 3y ago

I haven't worked with pgzx, but it's possible that memory management is easier. Zig uses memory arenas, and so does Postgres. If one can map directly to the other, it would be a huge win. With Rust/pgrx (which I have used, extensively) memory integration is more difficult. There's pg memory, and there's Rust memory, and they're not the same, and you have to play games to pass data between them. Lifetime issues crop up. Rust might be able to solve the problem in the future with custom allocators, but it's just not there yet.

bear9628 3y ago
> I haven't worked with pgzx, but it's possible that memory management is easier. Zig uses memory arenas, and so does Postgres. If one can map directly to the other, it would be a huge win. Yes. This was indeed a great motivator for using Zig. It was quite easy to integrate Zig with the Postgres memory management. This way we can use the Zig standard library or other Zig libraries without a second thought. Another advantage is that in Postgres memory context cleanup and error handling are somewhat well integrated with each other. This gives us some peace of mind as almost any Postgres function you might want to use in your extension is likely to raise an exception.

tudorg 3y ago

It's for sure the question that a lot of people have. Initially we had more details about that in the blog post, but we didn't want it to become a "Zig vs Rust" blog post, so we kept it to a minimum. I will expand just a little bit more here: First, I think the fact that Rust can be a trusted language for Postgres is a huge advantage, and I am excited about it! I hope we will have the chance to use it and contribute to pgrx as well. Postgres is not only written in C, but it has developed its own particular style of C code. For example: arena memory allocator (memory contexts), exceptions via setjmp/longjmp (ereport), single-threaded communicating via shared memory, SPI for accessing the data via SQL, etc. Some of these mechanisms kind of conflict with the way Rust likes to do things. Because of the above, pgrx has to do harder work to expose functionality. It's possible, just a lot of work. In Zig, we can use pretty much anything directly or with small wrappers. If you need to call into C a lot, you need to use unsafe, and that negates some of the memory safety advantages of Rust. Also, Rust unsafe code is harder to write.

weinzierl 3y ago

Here is talk and slides about how to create postgres extensions in Rust. https://rustlab.it/talks/teaching-an-old-dog-new-tricks-extending-postgres-capabilities-with-rust https://rustlab.it/talks/teaching-an-old-dog-new-tricks-exte...