feat: provide function to customize pgwire handlers (#103)

Signed-off-by: Ning Sun <sunning@greptime.com>

Author: sunng87

datafusion-postgres/src/handlers.rs

@@ -63,6 +63,7 @@ impl PgWireServerHandlers for HandlerFactory {
     }
 }
 
+/// The pgwire handler backed by a datafusion `SessionContext`
 pub struct DfSessionService {
     session_context: Arc<SessionContext>,
     parser: Arc<Parser>,

datafusion-postgres/src/lib.rs

@@ -10,6 +10,7 @@ use datafusion::prelude::SessionContext;
 pub mod auth;
 use getset::{Getters, Setters, WithSetters};
 use log::{info, warn};
+use pgwire::api::PgWireServerHandlers;
 use pgwire::tokio::process_socket;
 use rustls_pemfile::{certs, pkcs8_private_keys};
 use rustls_pki_types::{CertificateDer, PrivateKeyDer};
@@ -81,6 +82,18 @@ pub async fn serve(
     // Create the handler factory with authentication
     let factory = Arc::new(HandlerFactory::new(session_context, auth_manager));
 
+    serve_with_handlers(factory, opts).await
+}
+
+/// Serve with custom pgwire handlers
+///
+/// This function allows you to rewrite some of the built-in logic including
+/// authentication and query processing. You can Implement your own
+/// `PgWireServerHandlers` by reusing `DfSessionService`.
+pub async fn serve_with_handlers(
+    handlers: Arc<impl PgWireServerHandlers + Sync + Send + 'static>,
+    opts: &ServerOptions,
+) -> Result<(), std::io::Error> {
     // Set up TLS if configured
     let tls_acceptor =
         if let (Some(cert_path), Some(key_path)) = (&opts.tls_cert_path, &opts.tls_key_path) {
@@ -112,9 +125,8 @@ pub async fn serve(
     loop {
         match listener.accept().await {
             Ok((socket, _addr)) => {
-                let factory_ref = factory.clone();
+                let factory_ref = handlers.clone();
                 let tls_acceptor_ref = tls_acceptor.clone();
-                // Connection accepted from {addr} - log appropriately based on your logging strategy
 
                 tokio::spawn(async move {
                     if let Err(e) = process_socket(socket, tls_acceptor_ref, factory_ref).await {