Variable deduplication in query planner

apollo-router-core/Cargo.toml

@@ -29,6 +29,7 @@ http-body = "0.4.4"
 hyper = { version = "0.14.18", features = ["client"] }
 hyper-rustls = "0.23.0"
 include_dir = "0.7.2"
+indexmap = "1.8.1"
 itertools = "0.10.3"
 lazy_static = "1.4.0"
 lru = "0.7.5"

apollo-router-core/src/json_ext.rs

@@ -365,7 +365,7 @@ where
 /// A GraphQL path element that is composes of strings or numbers.
 /// e.g `/book/3/name`
 #[doc(hidden)]
-#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
+#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize, Hash)]
 #[serde(untagged)]
 pub enum PathElement {
     /// A path element that given an array will flatmap the content.
@@ -424,7 +424,7 @@ where
 ///
 /// This can be composed of strings and numbers
 #[doc(hidden)]
-#[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize, Default)]
+#[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize, Default, Hash)]
 #[serde(transparent)]
 pub struct Path(pub Vec<PathElement>);
 

apollo-router-core/src/plugins/include_subgraph_errors.rs

@@ -132,8 +132,8 @@ mod test {
 
         let account_mocks = vec![
             (
-                r#"{"query":"query TopProducts__accounts__3($representations:[_Any!]!){_entities(representations:$representations){...on User{name}}}","operationName":"TopProducts__accounts__3","variables":{"representations":[{"__typename":"User","id":"1"},{"__typename":"User","id":"2"},{"__typename":"User","id":"1"}]}}"#,
-                r#"{"data":{"_entities":[{"name":"Ada Lovelace"},{"name":"Alan Turing"},{"name":"Ada Lovelace"}]}}"#
+                r#"{"query":"query TopProducts__accounts__3($representations:[_Any!]!){_entities(representations:$representations){...on User{name}}}","operationName":"TopProducts__accounts__3","variables":{"representations":[{"__typename":"User","id":"1"},{"__typename":"User","id":"2"}]}}"#,
+                r#"{"data":{"_entities":[{"name":"Ada Lovelace"},{"name":"Alan Turing"}]}}"#
             )
         ].into_iter().map(|(query, response)| (serde_json::from_str(query).unwrap(), serde_json::from_str(response).unwrap())).collect();
         let account_service = MockSubgraph::new(account_mocks);
@@ -152,8 +152,8 @@ mod test {
                 r#"{"data":{"topProducts":[{"__typename":"Product","upc":"1","name":"Table"},{"__typename":"Product","upc":"2","name":"Couch"}]}}"#
             ),
             (
-                r#"{"query":"query TopProducts__products__2($representations:[_Any!]!){_entities(representations:$representations){...on Product{name}}}","operationName":"TopProducts__products__2","variables":{"representations":[{"__typename":"Product","upc":"1"},{"__typename":"Product","upc":"1"},{"__typename":"Product","upc":"2"}]}}"#,
-                r#"{"data":{"_entities":[{"name":"Table"},{"name":"Table"},{"name":"Couch"}]}}"#
+                r#"{"query":"query TopProducts__products__2($representations:[_Any!]!){_entities(representations:$representations){...on Product{name}}}","operationName":"TopProducts__products__2","variables":{"representations":[{"__typename":"Product","upc":"1"},{"__typename":"Product","upc":"2"}]}}"#,
+                r#"{"data":{"_entities":[{"name":"Table"},{"name":"Couch"}]}}"#
             )
             ].into_iter().map(|(query, response)| (serde_json::from_str(query).unwrap(), serde_json::from_str(response).unwrap())).collect();
 

apollo-router-core/src/query_planner/mod.rs

@@ -245,8 +245,9 @@ impl PlanNode {
 pub(crate) mod fetch {
     use super::selection::{select_object, Selection};
     use crate::prelude::graphql::*;
+    use indexmap::IndexSet;
     use serde::Deserialize;
-    use std::sync::Arc;
+    use std::{collections::HashMap, sync::Arc};
     use tower::ServiceExt;
     use tracing::{instrument, Instrument};
 
@@ -285,7 +286,7 @@ pub(crate) mod fetch {
 
     struct Variables {
         variables: Object,
-        paths: Vec<Path>,
+        paths: HashMap<Path, usize>,
     }
 
     impl Variables {
@@ -308,13 +309,20 @@ pub(crate) mod fetch {
                         .map(|(variable_key, value)| (variable_key.clone(), value.clone()))
                 }));
 
-                let mut paths = Vec::new();
-                let mut values = Vec::new();
+                let mut values: IndexSet<Value> = IndexSet::new();
+                let mut paths: HashMap<Path, usize> = HashMap::new();
                 data.select_values_and_paths(current_dir, |path, value| {
                     if let Value::Object(content) = value {
                         if let Ok(Some(value)) = select_object(content, requires, schema) {
-                            paths.push(path);
-                            values.push(value);
+                            match values.get_index_of(&value) {
+                                Some(index) => {
+                                    paths.insert(path, index);
+                                }
+                                None => {
+                                    paths.insert(path, values.len());
+                                    values.insert(value);
+                                }
+                            }
                         }
                     }
                 });
@@ -323,7 +331,7 @@ pub(crate) mod fetch {
                     return None;
                 }
 
-                variables.insert("representations", Value::Array(values));
+                variables.insert("representations", Value::Array(Vec::from_iter(values)));
 
                 Some(Variables { variables, paths })
             } else {
@@ -336,7 +344,7 @@ pub(crate) mod fetch {
                                 .map(|(variable_key, value)| (variable_key.clone(), value.clone()))
                         })
                         .collect::<Object>(),
-                    paths: Vec::new(),
+                    paths: HashMap::new(),
                 })
             }
         }
@@ -446,7 +454,7 @@ pub(crate) mod fetch {
         fn response_at_path<'a>(
             &'a self,
             current_dir: &'a Path,
-            paths: Vec<Path>,
+            paths: HashMap<Path, usize>,
             data: Value,
         ) -> Result<Value, FetchError> {
             if !self.requires.is_empty() {
@@ -458,9 +466,17 @@ pub(crate) mod fetch {
 
                         if let Value::Array(array) = entities {
                             let mut value = Value::default();
-
-                            for (entity, path) in array.into_iter().zip(paths.into_iter()) {
-                                value.insert(&path, entity)?;
+                            for (path, entity_idx) in paths {
+                                value.insert(
+                                    &path,
+                                    array
+                                        .get(entity_idx)
+                                        .ok_or_else(|| FetchError::ExecutionInvalidContent {
+                                            reason: "Received invalid content for key `_entities`!"
+                                                .to_string(),
+                                        })?
+                                        .clone(),
+                                )?;
                             }
                             return Ok(value);
                         } else {