perf(canvas): reduce Convex hot-path query load

convex/canvasGraph.ts

@@ -0,0 +1,66 @@
+import { v } from "convex/values";
+
+import type { Id } from "./_generated/dataModel";
+import { query, type QueryCtx } from "./_generated/server";
+import { requireAuth } from "./helpers";
+
+const PERFORMANCE_LOG_THRESHOLD_MS = 250;
+
+export async function loadCanvasGraph(
+  ctx: QueryCtx,
+  args: {
+    canvasId: Id<"canvases">;
+    userId: string;
+  },
+) {
+  const canvas = await ctx.db.get(args.canvasId);
+  if (!canvas || canvas.ownerId != args.userId) {
+    throw new Error("Canvas not found");
+  }
+
+  const [nodes, edges] = await Promise.all([
+    ctx.db
+      .query("nodes")
+      .withIndex("by_canvas", (q) => q.eq("canvasId", args.canvasId))
+      .collect(),
+    ctx.db
+      .query("edges")
+      .withIndex("by_canvas", (q) => q.eq("canvasId", args.canvasId))
+      .collect(),
+  ]);
+
+  return { canvas, nodes, edges };
+}
+
+export const get = query({
+  args: { canvasId: v.id("canvases") },
+  handler: async (ctx, { canvasId }) => {
+    const startedAt = Date.now();
+    const authStartedAt = Date.now();
+    const user = await requireAuth(ctx);
+    const authMs = Date.now() - authStartedAt;
+
+    const graphStartedAt = Date.now();
+    const { canvas, nodes, edges } = await loadCanvasGraph(ctx, {
+      canvasId,
+      userId: user.userId,
+    });
+    const graphMs = Date.now() - graphStartedAt;
+
+    const durationMs = Date.now() - startedAt;
+    if (durationMs >= PERFORMANCE_LOG_THRESHOLD_MS) {
+      console.warn("[canvasGraph.get] slow graph query", {
+        canvasId,
+        userId: user.userId,
+        authMs,
+        graphMs,
+        nodeCount: nodes.length,
+        edgeCount: edges.length,
+        canvasUpdatedAt: canvas.updatedAt,
+        durationMs,
+      });
+    }
+
+    return { nodes, edges };
+  },
+});