Fix pg_config version parsing (#5200)

## Problem
Fix pg_config version parsing

## Summary of changes
Use regex to capture major version of postgres
#5146

compute_tools/src/extension_server.rs

@@ -74,6 +74,7 @@ More specifically, here is an example ext_index.json
 use anyhow::Context;
 use anyhow::{self, Result};
 use compute_api::spec::RemoteExtSpec;
+use regex::Regex;
 use remote_storage::*;
 use serde_json;
 use std::io::Read;
@@ -108,14 +109,58 @@ pub fn get_pg_version(pgbin: &str) -> String {
     // pg_config --version returns a (platform specific) human readable string
     // such as "PostgreSQL 15.4". We parse this to v14/v15
     let human_version = get_pg_config("--version", pgbin);
-    if human_version.contains("15") {
-        return "v15".to_string();
-    } else if human_version.contains("14") {
-        return "v14".to_string();
+    return parse_pg_version(&human_version).to_string();
+}
+
+fn parse_pg_version(human_version: &str) -> &str {
+    match Regex::new(r"(?<major>\d+)\.(?<minor>\d+)")
+        .unwrap()
+        .captures(human_version)
+    {
+        Some(captures) if captures.len() == 3 => match &captures["major"] {
+            "14" => return "v14",
+            "15" => return "v15",
+            _ => {}
+        },
+        _ => {}
     }
     panic!("Unsuported postgres version {human_version}");
 }
 
+#[cfg(test)]
+mod tests {
+    use super::parse_pg_version;
+
+    #[test]
+    fn test_parse_pg_version() {
+        assert_eq!(parse_pg_version("PostgreSQL 15.4"), "v15");
+        assert_eq!(parse_pg_version("PostgreSQL 15.14"), "v15");
+        assert_eq!(
+            parse_pg_version("PostgreSQL 15.4 (Ubuntu 15.4-0ubuntu0.23.04.1)"),
+            "v15"
+        );
+
+        assert_eq!(parse_pg_version("PostgreSQL 14.15"), "v14");
+        assert_eq!(parse_pg_version("PostgreSQL 14.0"), "v14");
+        assert_eq!(
+            parse_pg_version("PostgreSQL 14.9 (Debian 14.9-1.pgdg120+1"),
+            "v14"
+        );
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_parse_pg_unsupported_version() {
+        parse_pg_version("PostgreSQL 13.14");
+    }
+
+    #[test]
+    #[should_panic]
+    fn test_parse_pg_incorrect_version_format() {
+        parse_pg_version("PostgreSQL 14");
+    }
+}
+
 // download the archive for a given extension,
 // unzip it, and place files in the appropriate locations (share/lib)
 pub async fn download_extension(