From eae5776dab4b82406969fb37150459ba02cddc55 Mon Sep 17 00:00:00 2001
From: seonghobae <8172694+seonghobae@users.noreply.github.com>
Date: Sun, 5 Jul 2026 21:15:51 +0000
Subject: [PATCH] =?UTF-8?q?=E2=9A=A1=20Bolt:=20ERD=20=EB=82=B4=EB=B3=B4?=
 =?UTF-8?q?=EB=82=B4=EA=B8=B0=20=EC=84=B1=EB=8A=A5=20=EC=B5=9C=EC=A0=81?=
 =?UTF-8?q?=ED=99=94=EB=A5=BC=20=EC=9C=84=ED=95=9C=20Map=20=EC=83=9D?=
 =?UTF-8?q?=EC=84=B1=20=EB=A3=A8=ED=94=84=20=EA=B0=9C=EC=84=A0?=
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---
 .jules/bolt.md             |  4 ++++
 frontend/src/erd/export.ts | 28 +++++++++++++++++++---------
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/.jules/bolt.md b/.jules/bolt.md
index b45f9caa..d4d55185 100644
--- a/.jules/bolt.md
+++ b/.jules/bolt.md
@@ -60,3 +60,7 @@ Optimized metric route processing to O(N) by creating a mapping of routes direct
 ## 2026-06-25 - Avoid Map allocations in frontend ERD loops and mutate asyncpg records in-place
 **Learning:** The frontend `snapshotToGraph` iterates over thousands of columns to generate the graph, so repeated lookups and redundant collection assignments increase GC pressure. Backend snapshot column dictionaries are freshly instantiated for the payload, so `add_column_examples` can safely fill missing fields in place.
 **Action:** Reuse existing collections while aggregating relational data, create `Map`/`Set` entries only on first use, and check for missing example fields before calling expensive inference helpers.
+
+## 2025-01-20 - Avoid array map allocations when initializing large Maps
+**Learning:** Initializing Maps with `new Map(array.map(...))` creates large intermediate arrays in memory (`[key, value][]`), resulting in unnecessary memory allocation, high GC pressure, and significantly worse performance during iterative processes (like diagram exports).
+**Action:** Prefer explicitly initializing a `new Map()` and populating it within a standard `for...of` loop over `new Map(array.map(...))` for high-frequency or large-scale data processing in the frontend.
\ No newline at end of file
diff --git a/frontend/src/erd/export.ts b/frontend/src/erd/export.ts
index b172947e..793fcb82 100644
--- a/frontend/src/erd/export.ts
+++ b/frontend/src/erd/export.ts
@@ -92,7 +92,11 @@ export function exportDDL(nodes: Node<TableNodeData>[], edges: Edge[]): string {
   let ddl = '-- Generated DDL\n\n';
 
   // Bolt: Use map for O(1) node lookup instead of O(N) array find
-  const nodesById = new Map(nodes.map(n => [n.id, n]));
+  // Bolt: Avoid array allocations via .map() when building Maps
+  const nodesById = new Map<string, Node<TableNodeData>>();
+  for (const n of nodes) {
+    nodesById.set(n.id, n);
+  }
 
   // Export tables
   for (const node of nodes) {
@@ -281,19 +285,25 @@ export function exportDiagramSvg(
   snapshot?: SnapshotJson | null,
 ): string {
   // Bolt: Use map for O(1) node lookup instead of O(N) array find
-  const nodesById = new Map(nodes.map(n => [n.id, n]));
+  // Bolt: Avoid array allocations via .map() when building Maps
+  const nodesById = new Map<string, Node<TableNodeData>>();
+  for (const n of nodes) {
+    nodesById.set(n.id, n);
+  }
   const width = 280;
   const headerHeight = 34;
   const rowHeight = 22;
   const padding = 40;
   const indexes = indexesByRelation(snapshot);
-  const heights = new Map(
-    nodes.map((node) => {
-      // ponytail: cap rendered index rows; add full index export when the canvas carries index nodes.
-      const indexRows = Math.min((indexes.get(node.id)?.length || 0) + (node.data.indexes?.length || 0), 8);
-      return [node.id, headerHeight + rowHeight * ((node.data.columns?.length || 0) + indexRows + (indexRows ? 1 : 0))];
-    }),
-  );
+
+  // Bolt: Avoid Map allocations with .map() inside loops for large graph exports
+  const heights = new Map<string, number>();
+  for (const node of nodes) {
+    // ponytail: cap rendered index rows; add full index export when the canvas carries index nodes.
+    const indexRows = Math.min((indexes.get(node.id)?.length || 0) + (node.data.indexes?.length || 0), 8);
+    heights.set(node.id, headerHeight + rowHeight * ((node.data.columns?.length || 0) + indexRows + (indexRows ? 1 : 0)));
+  }
+
   let minX = 0;
   let minY = 0;
   let maxX = width;