Compile Postgresql for 16k page size

micahc · July 23, 2025, 7:25am

Ok so my issue is with immich, which preloads vector.so nixpkgs/nixos/modules/services/web-apps/immich.nix at 2421b36eb4cb5324e63bc9772310a0993adae88e · NixOS/nixpkgs · GitHub

which is a rust crate that depends on another rust crate: pgvecto.rs/Cargo.toml at 2b290b34e8ba69104ea2f800fa53328c6ed6c236 · tensorchord/pgvecto.rs · GitHub

that vendors jemalloc and look it has a “fix” for ios.

github.com/tikv/jemallocator

jemalloc-sys/build.rs

5c5a9f79b


      
          .env("LDFLAGS", cflags.clone())
          .env("CPPFLAGS", cflags)
          .arg(format!("--with-version={je_version}"))
          .arg("--disable-cxx")
          .arg("--enable-doc=no")
          .arg("--enable-shared=no");
          
          if target.contains("ios") {
              // newer iOS deviced have 16kb page sizes:
              // closed: https://github.com/gnzlbg/jemallocator/issues/68
              cmd.arg("--with-lg-page=14");
          }
          
          // collect `malloc_conf` string:
          let mut malloc_conf = String::new();
          
          if let Some(bg) = BackgroundThreadSupport::new(&target) {
              // `jemalloc` is compiled with background thread run-time support on
              // available platforms by default so there is nothing to do to enable
              // it.

Not sure how to untangle that in nix though.

The rust package itself accepts the necessary environment variable: JEMALLOC_SYS_WITH_LG_PAGE

( crates.io: Rust Package Registry)

so I just need to override this vector-rs plugin that is deep in postgres’s build machinery.