feat: better error message for LIMIT parser

pgdog/Cargo.toml

@@ -78,6 +78,7 @@ azure_core = "0.34.0"
 crc32c = "0.6.8"
 bit-vec = "0.8"
 reqwest = { version = "0.12", default-features = false, features = ["rustls-tls-webpki-roots-no-provider"] }
+hex = "0.4"
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2"

pgdog/src/frontend/router/parser/error.rs

@@ -55,6 +55,9 @@ pub enum Error {
     #[error("missing parameter: ${0}")]
     MissingParameter(usize),
 
+    #[error("expected parameter ${0} to be an integer, got \'{1}\' instead")]
+    ParameterNotInteger(usize, String),
+
     #[error("column has no associated table")]
     ColumnNoTable,
 

pgdog/src/frontend/router/parser/limit.rs

@@ -52,12 +52,13 @@ impl<'a> LimitClause<'a> {
                     if param.is_null() {
                         Ok(None)
                     } else {
-                        Ok(Some(
-                            param
-                                .bigint()
-                                .ok_or(Error::MissingParameter(*number as usize))?
-                                as usize,
-                        ))
+                        match param.bigint() {
+                            Some(param) => Ok(Some(param as usize)),
+                            None => Err(Error::ParameterNotInteger(
+                                *number as usize,
+                                param.text_debug(),
+                            )),
+                        }
                     }
                 } else {
                     Ok(None)

pgdog/src/frontend/router/parser/query/test/test_select.rs

@@ -74,6 +74,45 @@ fn test_limit_offset_with_params() {
     assert_eq!(route.limit().offset, Some(25));
 }
 
+#[test]
+fn test_limit_offset_with_bad_params() {
+    let mut test = QueryParserTest::new();
+
+    let command = test.try_execute(vec![
+        Parse::named("__test_limit", "SELECT * FROM users LIMIT $1 OFFSET $2").into(),
+        Bind::new_params(
+            "__test_limit",
+            &[Parameter::new(b"apples"), Parameter::new(b"25")],
+        )
+        .into(),
+        Execute::new().into(),
+        Sync.into(),
+    ]);
+
+    let err = command.err().expect("limit should fail");
+    assert_eq!(
+        err.to_string(),
+        "expected parameter $1 to be an integer, got 'apples' instead"
+    );
+
+    let command = test.try_execute(vec![
+        Parse::named("__test_limit", "SELECT * FROM users LIMIT $1 OFFSET $2").into(),
+        Bind::new_params(
+            "__test_limit",
+            &[Parameter::new(b"25"), Parameter::new(b"oranges")],
+        )
+        .into(),
+        Execute::new().into(),
+        Sync.into(),
+    ]);
+
+    let err = command.err().expect("offset should fail");
+    assert_eq!(
+        err.to_string(),
+        "expected parameter $2 to be an integer, got 'oranges' instead"
+    );
+}
+
 #[test]
 fn test_distinct_row() {
     let mut test = QueryParserTest::new();

pgdog/src/net/messages/bind.rs

@@ -71,6 +71,15 @@ impl<'a> ParameterWithFormat<'a> {
         from_utf8(&self.parameter.data).ok()
     }
 
+    /// Get the parameter as a textual value for debugging purposes only.
+    pub fn text_debug(&self) -> String {
+        if let Some(text) = self.text() {
+            text.to_string()
+        } else {
+            hex::encode(self.data())
+        }
+    }
+
     /// Get BIGINT if one is encoded in the field.
     pub fn bigint(&self) -> Option<i64> {
         Self::decode(self)