⚡ Bolt: [performance improvement] optimize D1 query generation memory allocations

crates/flow/src/targets/d1.rs

@@ -300,40 +300,46 @@ impl D1ExportContext {
         key: &KeyValue,
         values: &FieldValues,
     ) -> Result<(String, Vec<serde_json::Value>), RecocoError> {
-        let mut columns = vec![];
-        let mut placeholders = vec![];
-        let mut params = vec![];
-        let mut update_clauses = vec![];
+        use std::fmt::Write;
+
+        // ⚡ Bolt: Use String::with_capacity and Write to avoid intermediate Vec allocations and format!
+        let mut params = Vec::with_capacity(self.key_fields_schema.len() + self.value_fields_schema.len());
+        let mut sql = String::with_capacity(256);
+        let _ = write!(sql, "INSERT INTO {} (", self.table_name);
 
-        // Extract key parts - KeyValue is a wrapper around Box<[KeyPart]>
-        for (idx, _key_field) in self.key_fields_schema.iter().enumerate() {
+        let mut num_columns = 0;
+        for (idx, key_field) in self.key_fields_schema.iter().enumerate() {
             if let Some(key_part) = key.0.get(idx) {
-                columns.push(self.key_fields_schema[idx].name.clone());
-                placeholders.push("?".to_string());
+                if num_columns > 0 { let _ = write!(sql, ", "); }
+                let _ = write!(sql, "{}", key_field.name);
                 params.push(key_part_to_json(key_part)?);
+                num_columns += 1;
             }
         }
-
-        // Add value fields
         for (idx, value) in values.fields.iter().enumerate() {
             if let Some(value_field) = self.value_fields_schema.get(idx) {
-                columns.push(value_field.name.clone());
-                placeholders.push("?".to_string());
+                if num_columns > 0 { let _ = write!(sql, ", "); }
+                let _ = write!(sql, "{}", value_field.name);
                 params.push(value_to_json(value)?);
-                update_clauses.push(format!(
-                    "{} = excluded.{}",
-                    value_field.name, value_field.name
-                ));
+                num_columns += 1;
             }
         }
 
-        let sql = format!(
-            "INSERT INTO {} ({}) VALUES ({}) ON CONFLICT DO UPDATE SET {}",
-            self.table_name,
-            columns.join(", "),
-            placeholders.join(", "),
-            update_clauses.join(", ")
-        );
+        let _ = write!(sql, ") VALUES (");
+        for i in 0..num_columns {
+            if i > 0 { let _ = write!(sql, ", "); }
+            let _ = write!(sql, "?");
+        }
+
+        let _ = write!(sql, ") ON CONFLICT DO UPDATE SET ");
+        let mut num_updates = 0;
+        for (idx, _value) in values.fields.iter().enumerate() {
+            if let Some(value_field) = self.value_fields_schema.get(idx) {
+                if num_updates > 0 { let _ = write!(sql, ", "); }
+                let _ = write!(sql, "{} = excluded.{}", value_field.name, value_field.name);
+                num_updates += 1;
+            }
+        }
 
         Ok((sql, params))
     }
@@ -342,22 +348,23 @@ impl D1ExportContext {
         &self,
         key: &KeyValue,
     ) -> Result<(String, Vec<serde_json::Value>), RecocoError> {
-        let mut where_clauses = vec![];
-        let mut params = vec![];
+        use std::fmt::Write;
 
-        for (idx, _key_field) in self.key_fields_schema.iter().enumerate() {
+        // ⚡ Bolt: Use String::with_capacity and Write to avoid intermediate Vec allocations and format!
+        let mut params = Vec::with_capacity(self.key_fields_schema.len());
+        let mut sql = String::with_capacity(128);
+        let _ = write!(sql, "DELETE FROM {} WHERE ", self.table_name);
+
+        let mut first = true;
+        for (idx, key_field) in self.key_fields_schema.iter().enumerate() {
             if let Some(key_part) = key.0.get(idx) {
-                where_clauses.push(format!("{} = ?", self.key_fields_schema[idx].name));
+                if !first { let _ = write!(sql, " AND "); }
+                let _ = write!(sql, "{} = ?", key_field.name);
                 params.push(key_part_to_json(key_part)?);
+                first = false;
             }
         }
 
-        let sql = format!(
-            "DELETE FROM {} WHERE {}",
-            self.table_name,
-            where_clauses.join(" AND ")
-        );
-
         Ok((sql, params))
     }