Server side parameters via with_param

Fixes #142

Author: serprex

src/lib.rs

@@ -5,7 +5,8 @@
 #[macro_use]
 extern crate static_assertions;
 
-use self::{error::Result, http_client::HttpClient};
+use self::{error::Result, http_client::HttpClient, sql::ser};
+use ::serde::Serialize;
 use std::{collections::HashMap, fmt::Display, sync::Arc};
 
 pub use self::{compression::Compression, row::Row};
@@ -160,6 +161,15 @@ impl Client {
         self
     }
 
+    /// Specify server side parameter for all this client's queries.
+    ///
+    /// See also [`Query::with_param`].
+    pub fn with_param(self, name: &str, value: impl Serialize) -> Result<Self, String> {
+        let mut param = String::from("");
+        ser::write_param(&mut param, &value)?;
+        Ok(self.with_option(format!("param_{name}"), param))
+    }
+
     /// Used to specify a header that will be passed to all queries.
     ///
     /// # Example

src/query.rs

@@ -1,5 +1,5 @@
 use hyper::{header::CONTENT_LENGTH, Method, Request};
-use serde::Deserialize;
+use serde::{Deserialize, Serialize};
 use std::fmt::Display;
 use url::Url;
 
@@ -10,7 +10,7 @@ use crate::{
     request_body::RequestBody,
     response::Response,
     row::Row,
-    sql::{Bind, SqlBuilder},
+    sql::{ser, Bind, SqlBuilder},
     Client,
 };
 
@@ -195,6 +195,19 @@ impl Query {
         self.client.add_option(name, value);
         self
     }
+
+    /// Specify server side parameter for query.
+    ///
+    /// In queries you can reference params as {name: type} e.g. {val: Int32}.
+    pub fn with_param(mut self, name: &str, value: impl Serialize) -> Self {
+        let mut param = String::from("");
+        if let Err(err) = ser::write_param(&mut param, &value) {
+            self.sql = SqlBuilder::Failed(format!("invalid param: {err}"));
+            self
+        } else {
+            self.with_option(format!("param_{name}"), param)
+        }
+    }
 }
 
 /// A cursor that emits rows.

src/sql/bind.rs

@@ -8,13 +8,13 @@ use super::{escape, ser};
 #[sealed]
 pub trait Bind {
     #[doc(hidden)]
-    fn write(&self, dst: impl fmt::Write) -> Result<(), String>;
+    fn write(&self, dst: &mut impl fmt::Write) -> Result<(), String>;
 }
 
 #[sealed]
 impl<S: Serialize> Bind for S {
     #[inline]
-    fn write(&self, mut dst: impl fmt::Write) -> Result<(), String> {
+    fn write(&self, mut dst: &mut impl fmt::Write) -> Result<(), String> {
         ser::write_arg(&mut dst, self)
     }
 }
@@ -26,7 +26,7 @@ pub struct Identifier<'a>(pub &'a str);
 #[sealed]
 impl<'a> Bind for Identifier<'a> {
     #[inline]
-    fn write(&self, dst: impl fmt::Write) -> Result<(), String> {
+    fn write(&self, dst: &mut impl fmt::Write) -> Result<(), String> {
         escape::identifier(self.0, dst).map_err(|err| err.to_string())
     }
 }

src/sql/escape.rs

@@ -1,35 +1,32 @@
 use std::fmt;
 
+// Trust clickhouse-connect https://github.com/ClickHouse/clickhouse-connect/blob/5d85563410f3ec378cb199ec51d75e033211392c/clickhouse_connect/driver/binding.py#L15
+
 // See https://clickhouse.tech/docs/en/sql-reference/syntax/#syntax-string-literal
-pub(crate) fn string(src: &str, dst: impl fmt::Write) -> fmt::Result {
-    escape(src, dst, '\'')
+pub(crate) fn string(src: &str, dst: &mut impl fmt::Write) -> fmt::Result {
+    dst.write_char('\'')?;
+    escape(src, dst)?;
+    dst.write_char('\'')
 }
 
 // See https://clickhouse.tech/docs/en/sql-reference/syntax/#syntax-identifiers
-pub(crate) fn identifier(src: &str, dst: impl fmt::Write) -> fmt::Result {
-    escape(src, dst, '`')
+pub(crate) fn identifier(src: &str, dst: &mut impl fmt::Write) -> fmt::Result {
+    dst.write_char('\'')?;
+    escape(src, dst)?;
+    dst.write_char('\'')
 }
 
-fn escape(src: &str, mut dst: impl fmt::Write, ch: char) -> fmt::Result {
-    dst.write_char(ch)?;
-
-    // TODO: escape newlines?
-    for (idx, part) in src.split(ch).enumerate() {
-        if idx > 0 {
-            dst.write_char('\\')?;
-            dst.write_char(ch)?;
-        }
-
-        for (idx, part) in part.split('\\').enumerate() {
-            if idx > 0 {
-                dst.write_str("\\\\")?;
-            }
-
-            dst.write_str(part)?;
-        }
+pub(crate) fn escape(src: &str, dst: &mut impl fmt::Write) -> fmt::Result {
+    const REPLACE: &[char] = &['\\', '\'', '`', '\t', '\n'];
+    let mut rest = src;
+    while let Some(nextidx) = rest.find(REPLACE) {
+        let (before, after) = rest.split_at(nextidx);
+        rest = &after[1..];
+        dst.write_str(before)?;
+        dst.write_char('\\')?;
+        dst.write_str(&after[..1])?;
     }
-
-    dst.write_char(ch)
+    dst.write_str(rest)
 }
 
 #[test]

src/sql/mod.rs

@@ -9,7 +9,7 @@ pub use bind::{Bind, Identifier};
 
 mod bind;
 pub(crate) mod escape;
-mod ser;
+pub(crate) mod ser;
 
 #[derive(Debug, Clone)]
 pub(crate) enum SqlBuilder {