Cargo Features
libpq has no features set by default.
[dependencies]
libpq = { version = "4.0.0", features = ["v11", "v12", "v13", "v14", "v15"] }Features from optional dependencies
In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.