Reduce allocations, prevent a String object creation unless required.

src/database/db_core.rs

@@ -36,7 +36,7 @@ pub enum Properties {
 }
 
 impl Properties {
-    pub fn id(&self) -> &String {
+    pub fn id(&self) -> &str {
         match self {
             Properties::Feature(id) => id,
             Properties::Unknown(id, _) => id,
@@ -268,7 +268,7 @@ impl Core {
         // Do we have this ID registered at all?
         if let Ok(offset) = self
             .properties
-            .binary_search_by_key(&&id, |properties| properties.id())
+            .binary_search_by_key(&id.as_str(), |properties| properties.id())
         {
             // Yes, so now let's find all the position linked to it, per
             // reference space
@@ -321,7 +321,7 @@ impl Core {
 
         if let Ok(offset) = self
             .properties
-            .binary_search_by_key(&&id, |properties| properties.id())
+            .binary_search_by_key(&id.as_str(), |properties| properties.id())
         {
             // Generate the search volume. Iterate over all reference spaces, to
             // retrieve a list of SpaceSetObjects linked to `id`, then iterate

src/database/space/axis.rs

@@ -139,8 +139,8 @@ impl Axis {
         })
     }
 
-    pub fn measurement_unit(&self) -> String {
-        self.measurement_unit.to_str().into()
+    pub fn measurement_unit(&self) -> &str {
+        self.measurement_unit.to_str()
     }
 
     pub fn unit_vector(&self) -> &Position {

src/database/space_db.rs

@@ -290,8 +290,7 @@ impl SpaceDB {
         let view_port = parameters.view_port(space);
 
         // Select the objects
-        let objects =
-            self.resolutions[index].find_by_value(&SpaceFields::new(self.name().into(), id.into()));
+        let objects = self.resolutions[index].find_by_value(&SpaceFields::new(self.name(), id));
 
         let results = if let Some(view_port) = view_port {
             objects

src/database/space_index.rs

@@ -22,10 +22,6 @@ impl SpaceSetObject {
         }
     }
 
-    pub fn id(&self) -> &Coordinate {
-        &self.value
-    }
-
     pub fn space_id(&self) -> &String {
         &self.space_id
     }
@@ -54,12 +50,11 @@ pub struct SpaceFields {
 }
 
 impl SpaceFields {
-    pub fn new(space_id: String, value: Coordinate) -> Self {
-        SpaceFields { space_id, value }
-    }
-
-    pub fn space_id(&self) -> &String {
-        &self.space_id
+    pub fn new(space_id: &str, value: usize) -> Self {
+        SpaceFields {
+            space_id: space_id.into(),
+            value: value.into(),
+        }
     }
 
     pub fn value(&self) -> &Coordinate {

src/json/model.rs

@@ -81,7 +81,7 @@ impl From<Axis> for space::Axis {
 impl From<&space::Axis> for Axis {
     fn from(axis: &space::Axis) -> Self {
         Axis {
-            measurement_unit: axis.measurement_unit(),
+            measurement_unit: axis.measurement_unit().into(),
             graduation: axis.graduation().into(),
             unit_vector: axis.unit_vector().into(),
         }
@@ -118,7 +118,7 @@ impl From<&&database::Properties> for Properties {
     fn from(p: &&database::Properties) -> Self {
         Properties {
             type_name: p.type_name().to_string(),
-            id: p.id().clone(),
+            id: p.id().into(),
         }
     }
 }