pg: set runtime parameters on startup

mason-postgres/src/lib.rs

@@ -96,9 +96,7 @@ impl Connection {
         _password: &'b str,
         database: &'b str,
     ) -> io::Result<()> {
-        let params = [("user", user), ("database", database)];
-
-        let msg = client::StartupMessage { params: &params };
+        let msg = client::StartupMessage { user, database: Some(database) };
         msg.serialize(&mut self.buf);
 
         self.writer.write_all(&self.buf).await?;

mason-postgres/src/protocol/client.rs

@@ -16,31 +16,63 @@ impl Terminate {
 
 #[derive(Debug)]
 pub struct StartupMessage<'a> {
-    /// One or more pairs of parameter name and value strings.
-    /// A zero byte is required as a terminator after the last name/value pair.
-    /// Parameters can appear in any order. user is required, others are optional.
-    pub params: &'a [(&'a str, &'a str)],
+    pub user: &'a str,
+    pub database: Option<&'a str>,
 }
 
 impl<'a> StartupMessage<'a> {
     pub fn serialize(&self, buf: &mut Vec<u8>) {
         with_length_prefix(buf, |buf| {
-            // version: 3 = major, 0 = minor
-            buf.extend_from_slice(&0x0003_0000_i32.to_be_bytes());
+            // protocol version: major = 3, minor = 0
+            buf.extend_from_slice(&0x0003_i16.to_be_bytes());
+            buf.extend_from_slice(&0x0000_i16.to_be_bytes());
 
-            for (name, value) in self.params {
-                buf.extend_from_slice(name.as_bytes());
-                buf.push(0);
-                buf.extend_from_slice(value.as_bytes());
-                buf.push(0);
+            write_str(buf, "user");
+            write_str(buf, self.user);
+
+            if let Some(database) = self.database {
+                write_str(buf, "database");
+                write_str(buf, database);
             }
 
+            // See this doc for more runtime parameters
+            // https://www.postgresql.org/docs/12/runtime-config-client.html
+
+            // Sets the display format for date and time values,
+            // as well as the rules for interpreting ambiguous date input values.
+            write_str(buf, "DateStyle");
+            write_str(buf, "ISO");
+
+            // Sets the display format for interval values.
+            write_str(buf, "IntervalStyle");
+            write_str(buf, "iso_8601");
+
+            // Sets the time zone for displaying and interpreting time stamps.
+            write_str(buf, "TimeZone");
+            write_str(buf, "UTC");
+
+            // Adjust postgres to return percise values for floats
+            // NOTE: This is default in postgres 12+
+            write_str(buf, "extra_float_digits");
+            write_str(buf, "3");
+
+            // Sets the client-side encoding (character set).
+            write_str(buf, "client_encoding");
+            write_str(buf, "UTF-8");
+
             // A zero byte is required as a terminator after the last name/value pair.
             buf.push(0);
         });
     }
 }
 
+// Write a string followed by a null-terminator
+#[inline]
+fn write_str(buf: &mut Vec<u8>, s: &str) {
+    buf.extend_from_slice(s.as_bytes());
+    buf.push(0);
+}
+
 // Write a variable amount of data into a buffer and then
 // prefix that data with the length of what was written
 fn with_length_prefix<F>(buf: &mut Vec<u8>, f: F)
@@ -63,18 +95,21 @@ where
 mod tests {
     use super::*;
 
-    // TODO: Serialize test more messages
+    // TODO: encode test more messages
 
     #[test]
     fn ser_startup_message() {
-        let msg = StartupMessage { params: &[("user", "postgres"), ("database", "postgres")] };
+        let msg = StartupMessage { user: "postgres", database: None };
 
         let mut buf = Vec::new();
-        msg.serialize(&mut buf);
+        msg.encode(&mut buf);
 
         assert_eq!(
-            "00000029000300007573657200706f73746772657\
-             300646174616261736500706f7374677265730000",
+            "00000074000300007573657200706f7374677265730044617465537\
+             4796c650049534f00496e74657276616c5374796c650069736f5f38\
+             3630310054696d655a6f6e65005554430065787472615f666c6f617\
+             45f646967697473003300636c69656e745f656e636f64696e670055\
+             54462d380000",
             hex::encode(buf)
         );
     }