optimise array encoding

proxy/src/serverless/json.rs

@@ -1,119 +1,113 @@
 use postgres_client::Row;
 use postgres_client::types::{Kind, Type};
-use serde::de::{Deserializer, Visitor};
+use serde::Deserialize;
+use serde::de::{Deserializer, IgnoredAny, Visitor};
 use serde_json::value::RawValue;
 use serde_json::{Map, Value};
 
-struct PgTextVisitor<'de>(&'de RawValue);
-impl<'de> Visitor<'de> for PgTextVisitor<'de> {
-    type Value = Option<String>;
-
-    fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
-        formatter.write_str("any valid JSON value")
-    }
-
-    // special care for nulls
-    fn visit_none<E>(self) -> Result<Self::Value, E> {
-        Ok(None)
-    }
-    fn visit_unit<E>(self) -> Result<Self::Value, E> {
-        Ok(None)
-    }
-
-    // convert to text with escaping
-    fn visit_bool<E>(self, _: bool) -> Result<Self::Value, E> {
-        Ok(Some(self.0.get().to_owned()))
-    }
-    fn visit_i64<E>(self, _: i64) -> Result<Self::Value, E> {
-        Ok(Some(self.0.get().to_owned()))
-    }
-    fn visit_u64<E>(self, _: u64) -> Result<Self::Value, E> {
-        Ok(Some(self.0.get().to_owned()))
-    }
-    fn visit_f64<E>(self, _: f64) -> Result<Self::Value, E> {
-        Ok(Some(self.0.get().to_owned()))
-    }
-    fn visit_map<A: serde::de::MapAccess<'de>>(self, _: A) -> Result<Self::Value, A::Error> {
-        Ok(Some(self.0.get().to_owned()))
-    }
-
-    // avoid escaping here, as we pass this as a parameter
-    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E> {
-        Ok(Some(v.to_string()))
-    }
-    fn visit_string<E>(self, v: String) -> Result<Self::Value, E> {
-        Ok(Some(v))
-    }
-
-    fn visit_seq<A: serde::de::SeqAccess<'de>>(self, mut seq: A) -> Result<Self::Value, A::Error> {
-        let mut output = String::new();
-        output.push('{');
-        let mut comma = false;
-        while let Some(val) = seq.next_element::<Value>()? {
-            if comma {
-                output.push(',');
-            }
-            comma = true;
-
-            let val = match val {
-                Value::Null => "NULL".to_string(),
-
-                // convert to text with escaping
-                // here string needs to be escaped, as it is part of the array
-                v @ (Value::Bool(_) | Value::Number(_) | Value::String(_)) => v.to_string(),
-                v @ Value::Object(_) => Value::String(v.to_string()).to_string(),
-
-                // recurse into array
-                Value::Array(arr) => json_array_to_pg_array(&arr),
-            };
-            output.push_str(&val);
-        }
-        output.push('}');
-        Ok(Some(output))
-    }
-}
-
 //
 // Convert json non-string types to strings, so that they can be passed to Postgres
 // as parameters.
 //
 pub(crate) fn json_to_pg_text(json: Vec<Box<RawValue>>) -> Vec<Option<String>> {
     json.into_iter()
-        .map(|raw| raw.deserialize_any(PgTextVisitor(&raw)).unwrap_or(None))
+        .map(|raw| {
+            match raw.get().as_bytes() {
+                // special handling for null.
+                b"null" => None,
+                // remove the escape characters from the string.
+                [b'"', ..] => {
+                    Some(String::deserialize(&*raw).expect("json should be a valid string"))
+                }
+                [b'[', ..] => {
+                    let mut output = String::with_capacity(raw.get().len());
+                    raw.deserialize_seq(PgArrayVisitor(&raw, &mut output))
+                        .expect("json should be a valid");
+                    Some(output)
+                }
+                // write all other values out directly
+                _ => Some(<Box<str>>::from(raw).into()),
+            }
+        })
         .collect()
 }
 
-//
-// Serialize a JSON array to a Postgres array. Contrary to the strings in the params
-// in the array we need to escape the strings. Postgres is okay with arrays of form
-// '{1,"2",3}'::int[], so we don't check that array holds values of the same type, leaving
-// it for Postgres to check.
-//
-// Example of the same escaping in node-postgres: packages/pg/lib/utils.js
-//
-fn json_array_to_pg_array(arr: &[Value]) -> String {
-    let mut output = String::new();
-    output.push('{');
-    for val in arr {
-        if output.len() > 1 {
-            output.push(',');
-        }
+struct PgArrayVisitor<'de, 'a>(&'de RawValue, &'a mut String);
 
-        let val = match val {
-            Value::Null => "NULL".to_string(),
-
-            // convert to text with escaping
-            // here string needs to be escaped, as it is part of the array
-            v @ (Value::Bool(_) | Value::Number(_) | Value::String(_)) => v.to_string(),
-            v @ Value::Object(_) => Value::String(v.to_string()).to_string(),
-
-            // recurse into array
-            Value::Array(arr) => json_array_to_pg_array(arr),
-        };
-        output.push_str(&val);
+impl PgArrayVisitor<'_, '_> {
+    #[inline]
+    #[allow(clippy::unnecessary_wraps)]
+    fn raw<E>(self) -> Result<(), E> {
+        self.1.push_str(self.0.get());
+        Ok(())
+    }
+}
+
+impl<'de> Visitor<'de> for PgArrayVisitor<'de, '_> {
+    type Value = ();
+
+    fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+        formatter.write_str("any valid JSON value")
+    }
+
+    // special care for nulls
+    fn visit_none<E>(self) -> Result<Self::Value, E> {
+        self.1.push_str("NULL");
+        Ok(())
+    }
+    fn visit_unit<E>(self) -> Result<Self::Value, E> {
+        self.1.push_str("NULL");
+        Ok(())
+    }
+
+    // convert to text with escaping
+    fn visit_bool<E>(self, _: bool) -> Result<Self::Value, E> {
+        self.raw()
+    }
+    fn visit_i64<E>(self, _: i64) -> Result<Self::Value, E> {
+        self.raw()
+    }
+    fn visit_u64<E>(self, _: u64) -> Result<Self::Value, E> {
+        self.raw()
+    }
+    fn visit_i128<E>(self, _: i128) -> Result<Self::Value, E> {
+        self.raw()
+    }
+    fn visit_u128<E>(self, _: u128) -> Result<Self::Value, E> {
+        self.raw()
+    }
+    fn visit_f64<E>(self, _: f64) -> Result<Self::Value, E> {
+        self.raw()
+    }
+    fn visit_str<E>(self, _: &str) -> Result<Self::Value, E> {
+        self.raw()
+    }
+
+    // an object needs re-escaping
+    fn visit_map<A: serde::de::MapAccess<'de>>(self, mut map: A) -> Result<Self::Value, A::Error> {
+        while map.next_entry::<IgnoredAny, IgnoredAny>()?.is_some() {}
+
+        let s = serde_json::to_string(self.0.get()).expect("a string should be valid json");
+        self.1.push_str(&s);
+        Ok(())
+    }
+
+    // write an array
+    fn visit_seq<A: serde::de::SeqAccess<'de>>(self, mut seq: A) -> Result<Self::Value, A::Error> {
+        self.1.push('{');
+        let mut comma = false;
+        while let Some(val) = seq.next_element::<&'de RawValue>()? {
+            if comma {
+                self.1.push(',');
+            }
+            comma = true;
+
+            val.deserialize_any(PgArrayVisitor(val, self.1))
+                .expect("all json values are valid");
+        }
+        self.1.push('}');
+        Ok(())
     }
-    output.push('}');
-    output
 }
 
 #[derive(Debug, thiserror::Error)]