Example of using PG ranges

Signed-off-by: itowlson <[email protected]>

Author: itowlson

Cargo.lock

@@ -59,6 +59,7 @@ members = [
   "examples/mysql",
   "examples/postgres",
   "examples/postgres-v3",
+  "examples/postgres-v4",
   "examples/redis-outbound",
   "examples/mqtt-outbound",
   "examples/variables",

Cargo.toml

@@ -0,0 +1,2 @@
+[build]
+target = "wasm32-wasip1"

examples/postgres-v4/.cargo/config.toml

@@ -0,0 +1,15 @@
+[package]
+name = "rust-outbound-pg-v4"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+crate-type = ["cdylib"]
+
+[dependencies]
+# Useful crate to handle errors.
+anyhow = "1"
+# General-purpose crate with common HTTP types.
+http = "1.0.0"
+# The Spin SDK.
+spin-sdk = { path = "../.." }

examples/postgres-v4/Cargo.toml

@@ -0,0 +1,36 @@
+# Spin Outbound PostgreSQL example
+
+This example shows how to access a PostgreSQL database from a Spin component.
+It shows the new PostgreSQL range support in the v4 interface.
+
+## Prerequisite: Postgres
+
+This example assumes postgres is running and accessible locally via its standard 5432 port.
+
+We suggest running the `postgres` Docker container which has the necessary postgres user permissions
+already configured. For example:
+
+```
+docker run --rm -h 127.0.0.1 -p 5432:5432 -e POSTGRES_HOST_AUTH_METHOD=trust postgres
+```
+
+## Spin up
+
+Then, run the following from the root of this example:
+
+```
+createdb -h localhost -U postgres spin_dev
+psql -h localhost -U postgres -d spin_dev -f db/testdata.sql
+spin build --up
+```
+
+Curl with a year between 2005 and today as the path:
+
+```
+$ curl -i localhost:3000/2016
+HTTP/1.1 200 OK
+transfer-encoding: chunked
+date: Mon, 18 Aug 2025 05:02:29 GMT
+
+Splodge and Fang and Kiki and Slats
+```

examples/postgres-v4/README.md

@@ -0,0 +1,14 @@
+CREATE TABLE cats (
+   name text not null,
+   reign int4range not null
+);
+
+INSERT INTO cats (name, reign) VALUES
+   ('Smoke', '[2005, 2013]'::int4range),
+   ('Splodge', '[2005, 2019]'::int4range),
+   ('Fang', '[2005, 2016]'::int4range),
+   ('Kiki', '[2005, 2020]'::int4range),
+   ('Slats', '[2005, 2021]'::int4range),
+   ('Rosie', '[2021,)'::int4range),
+   ('Hobbes', '[2021,)'::int4range)
+;

examples/postgres-v4/db/testdata.sql

@@ -0,0 +1,17 @@
+spin_manifest_version = 2
+
+[application]
+authors = ["Fermyon Engineering <[email protected]>"]
+name = "rust-outbound-pg-v4-example"
+version = "0.1.0"
+
+[[trigger.http]]
+route = "/:year"
+component = "outbound-pg"
+
+[component.outbound-pg]
+environment = { DB_URL = "host=localhost user=postgres dbname=spin_dev" }
+source = "../../target/wasm32-wasip1/release/rust_outbound_pg_v4.wasm"
+allowed_outbound_hosts = ["postgres://localhost"]
+[component.outbound-pg.build]
+command = "cargo build --target wasm32-wasip1 --release"

examples/postgres-v4/spin.toml

@@ -0,0 +1,42 @@
+#![allow(dead_code)]
+use anyhow::Result;
+use http::{Request, Response};
+use spin_sdk::{http_component, pg3, pg3::Decode};
+
+// The environment variable set in `spin.toml` that points to the
+// address of the Pg server that the component will write to
+const DB_URL_ENV: &str = "DB_URL";
+
+#[http_component]
+fn process(req: Request<()>) -> Result<Response<String>> {
+    let address = std::env::var(DB_URL_ENV)?;
+    let conn = pg3::Connection::open(&address)?;
+
+    let year_header = req
+        .headers()
+        .get("spin-path-match-year")
+        .map(|hv| hv.to_str())
+        .transpose()?
+        .unwrap_or("2025");
+    let year: i32 = year_header.parse()?;
+
+    // Due to an ambiguity in the PostgreSQL `<@` operator syntax, we MUST qualify
+    // the year as an int4 rather than an int4range in the query.
+    let rulers = conn.query(
+        "SELECT name FROM cats WHERE $1::int4 <@ reign",
+        &[year.into()],
+    )?;
+
+    let response = if rulers.rows.is_empty() {
+        "it was anarchy".to_owned()
+    } else {
+        let ruler_names = rulers
+            .rows
+            .into_iter()
+            .map(|r| Decode::decode(&r[0]))
+            .collect::<Result<Vec<String>, _>>()?;
+        ruler_names.join(" and ")
+    };
+
+    Ok(http::Response::builder().body(format!("{response}\n"))?)
+}