fix: Fix query error on ClickHouse Query latency chart (#1978)

## Summary

This PR fixes the heatmap Query Latency chart on the ClickHouse page, by casting the value expression to Float64 so that it matches the type of other `greatest()` args.

### Screenshots or video

Before

<img width="2301" height="341" alt="Screenshot 2026-03-24 at 10 29 44 AM" src="https://github.com/user-attachments/assets/4c3c2562-e2c8-4bc8-8739-adb7768d7cf6" />
<img width="1945" height="304" alt="Screenshot 2026-03-24 at 10 29 35 AM" src="https://github.com/user-attachments/assets/5d8d3dd0-bf56-4af8-bfe9-7672723c255b" />

After

<img width="2290" height="367" alt="Screenshot 2026-03-24 at 10 33 29 AM" src="https://github.com/user-attachments/assets/af034dbd-d983-416b-9b47-927db818bd02" />
<img width="2296" height="299" alt="Screenshot 2026-03-24 at 10 33 38 AM" src="https://github.com/user-attachments/assets/e5910d8d-e799-444d-b38d-8fa574beae87" />


### How to test locally or on Vercel

This can be validated in the preview environment

### References



- Linear Issue: Closes HDX-3794
- Related PRs:

.changeset/few-ravens-teach.md

@@ -0,0 +1,5 @@
+---
+"@hyperdx/app": patch
+---
+
+fix: Fix query error on ClickHouse Query latency chart

packages/app/src/components/DBHeatmapChart.tsx

@@ -454,11 +454,11 @@ function HeatmapContainer({
   // For linear scale: bucket by raw value (original behavior)
   const bucketExprAgg =
     scaleType === 'log'
-      ? `widthBucket(log(greatest(value_calc, ${effectiveMin})), log(${effectiveMin}), log(${max}), ${nBuckets})`
+      ? `widthBucket(log(greatest(toFloat64(value_calc), ${effectiveMin})), log(${effectiveMin}), log(${max}), ${nBuckets})`
       : `widthBucket(value_calc, ${effectiveMin}, ${max}, ${nBuckets})`;
   const bucketExprDirect =
     scaleType === 'log'
-      ? `widthBucket(log(greatest(${valueExpression}, ${effectiveMin})), log(${effectiveMin}), log(${max}), ${nBuckets})`
+      ? `widthBucket(log(greatest(toFloat64(${valueExpression}), ${effectiveMin})), log(${effectiveMin}), log(${max}), ${nBuckets})`
       : `widthBucket(${valueExpression}, ${effectiveMin}, ${max}, ${nBuckets})`;
 
   const bucketConfig: BuilderChartConfigWithDateRange = isAggregateExpression

packages/app/tests/e2e/features/clickhouse-dashboard.spec.ts

@@ -0,0 +1,21 @@
+import { ClickHouseDashboardPage } from '../page-objects/ClickHouseDashboardPage';
+import { expect, test } from '../utils/base-test';
+
+test.describe('ClickHouse Dashboard', { tag: ['@full-stack'] }, () => {
+  let clickhousePage: ClickHouseDashboardPage;
+
+  test.beforeEach(async ({ page }) => {
+    clickhousePage = new ClickHouseDashboardPage(page);
+  });
+
+  test('should load heatmap chart without error', async () => {
+    await clickhousePage.goto();
+    await clickhousePage.waitForPageLoad();
+
+    // Select the local connection
+    await clickhousePage.selectConnection('local');
+
+    // Assert the heatmap rendered without error
+    await expect(await clickhousePage.queryLatencyChart).toBeVisible();
+  });
+});

packages/app/tests/e2e/page-objects/ClickHouseDashboardPage.ts

@@ -0,0 +1,45 @@
+/**
+ * ClickHouseDashboardPage - Page object for the /clickhouse dashboard page
+ * Encapsulates interactions with the ClickHouse system dashboard
+ */
+import { Locator, Page } from '@playwright/test';
+
+export class ClickHouseDashboardPage {
+  readonly page: Page;
+  private readonly _pageContainer: Locator;
+  private readonly _queryLatencyChart: Locator;
+  private readonly _connectionSelect: Locator;
+
+  constructor(page: Page) {
+    this.page = page;
+    this._pageContainer = page.getByTestId('clickhouse-dashboard-page');
+    // Scope heatmap locators to the chart container with the "Query Latency" title
+    this._queryLatencyChart = this._pageContainer
+      .locator('div')
+      .filter({ hasText: 'Query Latency' })
+      .first();
+    this._connectionSelect = page.getByPlaceholder('Connection');
+  }
+
+  async goto() {
+    await this.page.goto('/clickhouse');
+  }
+
+  async selectConnection(connectionName: string) {
+    await this._connectionSelect.click();
+    const option = this.page.getByRole('option', { name: connectionName });
+    await option.click();
+  }
+
+  async waitForPageLoad() {
+    await this._pageContainer.waitFor({ state: 'visible' });
+  }
+
+  get container(): Locator {
+    return this._pageContainer;
+  }
+
+  get queryLatencyChart(): Locator {
+    return this._queryLatencyChart.locator('.uplot');
+  }
+}