From 7d34fe6339912bf8cd3d45480fab72dd2cadd391 Mon Sep 17 00:00:00 2001
From: Peter van der Zee <github-public@qfox.nl>
Date: Wed, 14 Oct 2020 15:26:41 +0200
Subject: [PATCH] perf(gatsby-source-contentful): do not linear search on a
 potentially large set

---
 .../gatsby-source-contentful/src/gatsby-node.js    | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/packages/gatsby-source-contentful/src/gatsby-node.js b/packages/gatsby-source-contentful/src/gatsby-node.js
index 6de12f80d616b..cefec99c9e675 100644
--- a/packages/gatsby-source-contentful/src/gatsby-node.js
+++ b/packages/gatsby-source-contentful/src/gatsby-node.js
@@ -196,25 +196,23 @@ exports.sourceNodes = async (
   // Create a map of up to date entries and assets
   function mergeSyncData(previous, current, deleted) {
     const entryMap = new Map()
-    previous.forEach(
-      e => !deleted.includes(e.sys.id) && entryMap.set(e.sys.id, e)
-    )
-    current.forEach(
-      e => !deleted.includes(e.sys.id) && entryMap.set(e.sys.id, e)
-    )
+    previous.forEach(e => !deleted.has(e.sys.id) && entryMap.set(e.sys.id, e))
+    current.forEach(e => !deleted.has(e.sys.id) && entryMap.set(e.sys.id, e))
     return [...entryMap.values()]
   }
 
+  const deletedSet = new Set(currentSyncData.deletedEntries.map(e => e.sys.id))
+
   const mergedSyncData = {
     entries: mergeSyncData(
       previousSyncData.entries,
       currentSyncData.entries,
-      currentSyncData.deletedEntries.map(e => e.sys.id)
+      deletedSet
     ),
     assets: mergeSyncData(
       previousSyncData.assets,
       currentSyncData.assets,
-      currentSyncData.deletedAssets.map(e => e.sys.id)
+      deletedSet
     ),
   }