From 02c2a34a62c3717a4885449172e404f19ebf66c9 Mon Sep 17 00:00:00 2001
From: "Sachin D. Shinde" <sachin@apollographql.com>
Date: Wed, 21 Aug 2024 10:37:41 -0700
Subject: [PATCH] Avoid unnecessary array copying in
 `ConditionValidationState.advance()` (#3109)

We were using `concat()` in `ConditionValidationState.advance()`, which
was frequently copying the array. Shifting this to use `push()` instead
increases performance significantly for some graphs.
---
 .changeset/fast-points-wonder.md            | 7 +++++++
 query-graphs-js/src/conditionsValidation.ts | 4 ++--
 2 files changed, 9 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/fast-points-wonder.md

diff --git a/.changeset/fast-points-wonder.md b/.changeset/fast-points-wonder.md
new file mode 100644
index 000000000..710f230b1
--- /dev/null
+++ b/.changeset/fast-points-wonder.md
@@ -0,0 +1,7 @@
+---
+"@apollo/federation-internals": patch
+"@apollo/gateway": patch
+"@apollo/composition": patch
+---
+
+Reduce memory overhead during satisfiability checking when there are many options.
diff --git a/query-graphs-js/src/conditionsValidation.ts b/query-graphs-js/src/conditionsValidation.ts
index 7bae900ad..7763c170c 100644
--- a/query-graphs-js/src/conditionsValidation.ts
+++ b/query-graphs-js/src/conditionsValidation.ts
@@ -25,7 +25,7 @@ class ConditionValidationState {
   ) {}
 
   advance(supergraph: Schema): ConditionValidationState[] | null {
-    let newOptions: SimultaneousPathsWithLazyIndirectPaths[] = [];
+    const newOptions: SimultaneousPathsWithLazyIndirectPaths[] = [];
     for (const paths of this.subgraphOptions) {
       const pathsOptions = advanceSimultaneousPathsWithOperation(
         supergraph,
@@ -40,7 +40,7 @@ class ConditionValidationState {
       if (!pathsOptions) {
         continue;
       }
-      newOptions = newOptions.concat(pathsOptions);
+      newOptions.push(...pathsOptions);
     }
 
     // If we got no options, it means that particular selection of the conditions cannot be satisfied, so the