fusion/docs/performance/dashboard-load.md

Dashboard Load Performance Analysis

Date: 2026-04-10 Task: FN-1532

Executive Summary

Profile analysis identified several SQLite query performance issues in the dashboard boot path. These issues cause unnecessary full table scans and temp B-tree sorts that slow dashboard load times, especially as project data grows.

Methodology

1. Created a test database with representative data:

   • 100 tasks
   • 50 AI sessions
   • 200 activity log entries
   • 100 run audit events

2. Analyzed query plans using EXPLAIN QUERY PLAN for boot-critical read operations

Query Plan Analysis Results

Issue 1: Tasks List with ORDER BY (CRITICAL)

Query: SELECT * FROM tasks ORDER BY createdAt ASC

Before:

SCAN tasks
USE TEMP B-TREE FOR ORDER BY

Problem: Full table scan with in-memory sorting. As the tasks table grows, this becomes increasingly expensive.

Solution: Add idxTasksCreatedAt on tasks(createdAt) - allows index scan with ordered retrieval.

---

Issue 2: AI Sessions Active List (HIGH)

Query: SELECT ... FROM ai_sessions WHERE status IN ('generating', 'awaiting_input', 'error') ORDER BY updatedAt DESC

Before:

SEARCH ai_sessions USING INDEX idxAiSessionsStatus (status=?)
USE TEMP B-TREE FOR ORDER BY

Problem: The existing idxAiSessionsStatus only indexes on status, but the query also needs updatedAt for ordering. This requires a temp B-tree to sort results.

Solution: Add idxAiSessionsStatusUpdatedAt on ai_sessions(status, updatedAt DESC) - covers both filtering and sorting.

---

Issue 3: Activity Log by Task ID (MEDIUM)

Query: SELECT * FROM activityLog WHERE taskId = ? ORDER BY timestamp DESC

Before:

SEARCH activityLog USING INDEX idxActivityLogTaskId (taskId=?)
USE TEMP B-TREE FOR ORDER BY

Problem: The existing idxActivityLogTaskId only indexes taskId, but the query also needs timestamp for ordering.

Solution: Add idxActivityLogTaskIdTimestamp on activityLog(taskId, timestamp DESC) - covers both filtering and ordering.

---

Issue 4: Activity Log by Type (MEDIUM)

Query: SELECT * FROM activityLog WHERE type = ? ORDER BY timestamp DESC

Before:

SEARCH activityLog USING INDEX idxActivityLogType (type=?)
USE TEMP B-TREE FOR ORDER BY

Problem: Similar to task ID - the type index doesn't include timestamp for ordering.

Solution: Add idxActivityLogTypeTimestamp on activityLog(type, timestamp DESC) - covers both filtering and ordering.

---

Issue 5: Agent Heartbeats List (MEDIUM)

Query: SELECT * FROM agentHeartbeats WHERE agentId = ? ORDER BY timestamp DESC

Before:

SEARCH agentHeartbeats USING INDEX idxAgentHeartbeatsAgentId (agentId=?)
USE TEMP B-TREE FOR ORDER BY

Problem: The agent heartbeat index doesn't include timestamp for ordering.

Solution: Add idxAgentHeartbeatsAgentIdTimestamp on agentHeartbeats(agentId, timestamp DESC) - covers both filtering and ordering.

---

Issue 6: Agents by State (LOW)

Query: SELECT * FROM agents WHERE state = 'idle'

Before:

SCAN agents

Problem: Full table scan on agents table. This affects any dashboard views that filter agents by state.

Solution: Add idxAgentsState on agents(state) - allows index-based lookup for state filtering.

---

Proposed Index Changes

Index Name	Table	Columns	Purpose
idxTasksCreatedAt	tasks	createdAt	Avoid temp B-tree for ORDER BY createdAt
idxAiSessionsStatusUpdatedAt	ai_sessions	status, updatedAt DESC	Cover status filter + updatedAt ordering
idxActivityLogTaskIdTimestamp	activityLog	taskId, timestamp DESC	Cover taskId filter + timestamp ordering
idxActivityLogTypeTimestamp	activityLog	type, timestamp DESC	Cover type filter + timestamp ordering
idxAgentHeartbeatsAgentIdTimestamp	agentHeartbeats	agentId, timestamp DESC	Cover agentId filter + timestamp ordering
idxAgentsState	agents	state	Avoid full scan for state filtering

Impact Assessment

• Boot time improvement: The listTasks index is the highest impact - it eliminates a full table scan + sort on every dashboard load
• AI sessions: Eliminates sort overhead on every session list refresh
• Activity log: Eliminates sort overhead on task detail views
• Agents: Eliminates full scan on agent list filtering

Files Modified

• packages/core/src/db.ts - Add migration for new indexes
• packages/core/src/db.test.ts - Update expected index list
• packages/core/src/run-audit.test.ts - Update expected index list
• packages/core/src/__tests__/task-documents.test.ts - Update expected index list