|
| 1 | +# Lazy Loading Implementation |
| 2 | + |
| 3 | +**Date**: 2025-10-31 |
| 4 | +**Purpose**: Improve perceived performance of Cesium tutorial page |
| 5 | + |
| 6 | +--- |
| 7 | + |
| 8 | +## π― What Was Implemented |
| 9 | + |
| 10 | +### 1. **Chunked Rendering for Geocode Points** (lines 194-229) |
| 11 | + |
| 12 | +**Problem**: Rendering thousands of geocode points in one blocking operation made the page unresponsive. |
| 13 | + |
| 14 | +**Solution**: Render points in batches of 500 with yields to browser event loop. |
| 15 | + |
| 16 | +```javascript |
| 17 | +const CHUNK_SIZE = 500; |
| 18 | +for (let i = 0; i < data.length; i += CHUNK_SIZE) { |
| 19 | + const chunk = data.slice(i, i + CHUNK_SIZE); |
| 20 | + // ... add points for chunk |
| 21 | + |
| 22 | + // Yield to browser between chunks |
| 23 | + if (i + CHUNK_SIZE < data.length) { |
| 24 | + await new Promise(resolve => setTimeout(resolve, 0)); |
| 25 | + } |
| 26 | +} |
| 27 | +``` |
| 28 | + |
| 29 | +**Benefits**: |
| 30 | +- Page remains interactive during rendering |
| 31 | +- User sees progress (not just a frozen browser) |
| 32 | +- Can cancel/navigate away during load if needed |
| 33 | + |
| 34 | +--- |
| 35 | + |
| 36 | +### 2. **Dynamic Progress Indicator** (lines 203-207) |
| 37 | + |
| 38 | +**Problem**: User had no feedback during slow initial load. |
| 39 | + |
| 40 | +**Solution**: Update loading div with real-time progress. |
| 41 | + |
| 42 | +```javascript |
| 43 | +if (loadingDiv) { |
| 44 | + const pct = Math.round((endIdx / data.length) * 100); |
| 45 | + loadingDiv.innerHTML = `Rendering geocodes... ${endIdx.toLocaleString()}/${data.length.toLocaleString()} (${pct}%)`; |
| 46 | +} |
| 47 | +``` |
| 48 | + |
| 49 | +**User Experience**: |
| 50 | +- "Querying geocodes from parquet..." (during SQL query) |
| 51 | +- "Rendering geocodes... 500/1,234 (41%)" (during rendering) |
| 52 | +- Progress hidden when complete |
| 53 | + |
| 54 | +--- |
| 55 | + |
| 56 | +### 3. **Performance Telemetry** (lines 132-244) |
| 57 | + |
| 58 | +**Problem**: No visibility into where time is spent. |
| 59 | + |
| 60 | +**Solution**: Use Performance API to measure each phase. |
| 61 | + |
| 62 | +**Measurements Added**: |
| 63 | +1. **locations-query**: Time to execute SQL query (lines 168-173) |
| 64 | +2. **locations-render**: Time to render all points (lines 230-232) |
| 65 | +3. **locations-total**: Total time from start to finish (lines 239-241) |
| 66 | + |
| 67 | +**Console Output**: |
| 68 | +```javascript |
| 69 | +Query executed in 2847ms - retrieved 1234 locations |
| 70 | +Rendering completed in 412ms |
| 71 | +Total time (query + render): 3259ms |
| 72 | +``` |
| 73 | + |
| 74 | +--- |
| 75 | + |
| 76 | +### 4. **Query Telemetry for Click Events** (lines 400-406, 462-468, 524-530) |
| 77 | + |
| 78 | +**Problem**: No visibility into per-query performance when user clicks geocode. |
| 79 | + |
| 80 | +**Solution**: Added timing to all three query functions. |
| 81 | + |
| 82 | +**Added to**: |
| 83 | +- `get_samples_1()` - Path 1 (direct event location) |
| 84 | +- `get_samples_2()` - Path 2 (via site location) |
| 85 | +- `get_samples_at_geo_cord_location_via_sample_event()` - Eric's query |
| 86 | + |
| 87 | +**Console Output**: |
| 88 | +```javascript |
| 89 | +Path 1 query executed in 1523ms - retrieved 5 samples |
| 90 | +Path 2 query executed in 892ms - retrieved 0 samples |
| 91 | +Eric's query executed in 1401ms - retrieved 5 samples |
| 92 | +``` |
| 93 | +
|
| 94 | +--- |
| 95 | +
|
| 96 | +## π Expected Performance Improvements |
| 97 | +
|
| 98 | +### Before Lazy Loading: |
| 99 | +- **Initial load**: Page frozen for 5-10 seconds (no feedback) |
| 100 | +- **User perception**: "Is this working? Did it crash?" |
| 101 | +- **Browser**: Unresponsive during point rendering |
| 102 | +
|
| 103 | +### After Lazy Loading: |
| 104 | +- **Query phase**: 2-8 seconds (depends on parquet download) |
| 105 | + - User sees: "Querying geocodes from parquet..." |
| 106 | +- **Rendering phase**: 400-800ms (chunked, with progress) |
| 107 | + - User sees: "Rendering geocodes... 500/1,234 (41%)" |
| 108 | +- **Total perceived wait**: Same absolute time, but **feels 3-5x faster** due to feedback |
| 109 | +- **Browser**: Remains responsive (can scroll, type, navigate) |
| 110 | +
|
| 111 | +### Click Performance (no change): |
| 112 | +- Path 1, Path 2, Eric's queries: Still 1-2 seconds each (structural limitation) |
| 113 | +- Now visible via console telemetry for optimization planning |
| 114 | + |
| 115 | +--- |
| 116 | + |
| 117 | +## π§ͺ Testing Instructions |
| 118 | + |
| 119 | +### 1. Open Browser Developer Console |
| 120 | + |
| 121 | +**Chrome/Edge**: F12 or Cmd+Option+I (Mac) |
| 122 | +**Firefox**: F12 or Cmd+Option+K (Mac) |
| 123 | + |
| 124 | +### 2. Load the Page |
| 125 | + |
| 126 | +Navigate to: `http://localhost:5860/tutorials/parquet_cesium.html` |
| 127 | + |
| 128 | +### 3. Observe Initial Load |
| 129 | + |
| 130 | +**Watch for**: |
| 131 | +- Loading indicator updates: "Querying geocodes..." β "Rendering... X/Y (Z%)" |
| 132 | +- Console logs with timing measurements |
| 133 | +- Page remains responsive (try scrolling, clicking buttons) |
| 134 | + |
| 135 | +**Expected Console Output**: |
| 136 | +``` |
| 137 | +Query executed in 2847ms - retrieved 1234 locations |
| 138 | +Rendering completed in 412ms |
| 139 | +Total time (query + render): 3259ms |
| 140 | +``` |
| 141 | +
|
| 142 | +### 4. Test Click Queries |
| 143 | +
|
| 144 | +**Steps**: |
| 145 | +1. Click any geocode point on globe |
| 146 | +2. Observe three query results tables render |
| 147 | +3. Check console for query timings |
| 148 | +
|
| 149 | +**Expected Console Output**: |
| 150 | +``` |
| 151 | +Path 1 query executed in 1523ms - retrieved 5 samples |
| 152 | +Path 2 query executed in 892ms - retrieved 0 samples |
| 153 | +Eric's query executed in 1401ms - retrieved 5 samples |
| 154 | +``` |
| 155 | +
|
| 156 | +### 5. Test with Known Geocode |
| 157 | +
|
| 158 | +**Use search box**: |
| 159 | +- Enter: `geoloc_04d6e816218b1a8798fa90b3d1d43bf4c043a57f` (PKAP with samples) |
| 160 | +- Click search |
| 161 | +- Verify camera flies to location |
| 162 | +- Verify all three tables render |
| 163 | +- Check console timings |
| 164 | +
|
| 165 | +--- |
| 166 | +
|
| 167 | +## π Performance Baseline Data |
| 168 | +
|
| 169 | +Once you test locally, we can establish baseline metrics: |
| 170 | +
|
| 171 | +**Initial Load Metrics**: |
| 172 | +- Query time: _____ ms |
| 173 | +- Render time: _____ ms |
| 174 | +- Total time: _____ ms |
| 175 | +- Number of geocodes: _____ |
| 176 | +
|
| 177 | +**Click Query Metrics**: |
| 178 | +- Path 1: _____ ms (_____ samples) |
| 179 | +- Path 2: _____ ms (_____ samples) |
| 180 | +- Eric's query: _____ ms (_____ samples) |
| 181 | +
|
| 182 | +These baselines will help evaluate whether Phase 2 optimizations (pre-aggregated parquet) are worth pursuing. |
| 183 | +
|
| 184 | +--- |
| 185 | +
|
| 186 | +## π Next Steps (from PERFORMANCE_OPTIMIZATION_PLAN.md) |
| 187 | +
|
| 188 | +### Phase 1 Complete β
|
| 189 | +- [x] Chunked rendering with progress |
| 190 | +- [x] Performance telemetry |
| 191 | +- [x] Dynamic loading indicators |
| 192 | +
|
| 193 | +### Phase 2 (If Needed) - Structural Optimization |
| 194 | +**Goal**: Reduce initial load from 3-8 seconds β <1 second |
| 195 | +
|
| 196 | +**Approach**: Pre-aggregate geocode classification query |
| 197 | +1. Create `oc_geocodes_classified.parquet` (~50KB) via server-side script |
| 198 | +2. Replace expensive CTE query with simple `SELECT * FROM read_parquet(...)` |
| 199 | +3. Automate regeneration in GitHub Actions workflow |
| 200 | +
|
| 201 | +**When to pursue**: |
| 202 | +- If query time consistently >5 seconds |
| 203 | +- If users complain about initial load |
| 204 | +- If baseline data shows query is primary bottleneck |
| 205 | +
|
| 206 | +### Phase 3 (Only if Desperate) - Deep Optimization |
| 207 | +**Goal**: Reduce click queries from 1-2 seconds β 200-400ms |
| 208 | +
|
| 209 | +**Approach**: Denormalized edge indexes (see PERFORMANCE_OPTIMIZATION_PLAN.md) |
| 210 | +
|
| 211 | +**When to pursue**: |
| 212 | +- Only if click query performance is unacceptable |
| 213 | +- After Phase 2 is complete |
| 214 | +- If baseline data shows queries are consistently >2 seconds |
| 215 | +
|
| 216 | +--- |
| 217 | +
|
| 218 | +## π Debugging Tips |
| 219 | +
|
| 220 | +### If Progress Indicator Not Visible: |
| 221 | +- Check: Is `loading_1` div hidden by CSS? |
| 222 | +- Check: Browser console for JavaScript errors |
| 223 | +- Verify: `loadingDiv.hidden = false` is executing (add console.log) |
| 224 | +
|
| 225 | +### If Console Logs Missing: |
| 226 | +- Verify: Browser console is set to show "Verbose" or "All" messages |
| 227 | +- Check: Performance API available (`typeof performance !== 'undefined'`) |
| 228 | +- Verify: No JavaScript errors blocking execution |
| 229 | +
|
| 230 | +### If Page Still Freezes: |
| 231 | +- Reduce CHUNK_SIZE from 500 β 100 (more yields, slower but more responsive) |
| 232 | +- Check: Browser is not in "Performance" mode (some browsers batch setTimeout) |
| 233 | +- Verify: `await new Promise(...)` is actually yielding (test with longer timeout) |
| 234 | +
|
| 235 | +--- |
| 236 | +
|
| 237 | +## π‘ Code Changes Summary |
| 238 | +
|
| 239 | +**File Modified**: `tutorials/parquet_cesium.qmd` |
| 240 | +
|
| 241 | +**Lines Changed**: |
| 242 | +- 131-248: Enhanced `locations` query with telemetry + chunked rendering (+110 lines) |
| 243 | +- 400-406: Added telemetry to `get_samples_1()` (+6 lines) |
| 244 | +- 462-468: Added telemetry to `get_samples_2()` (+6 lines) |
| 245 | +- 524-530: Added telemetry to `get_samples_at_geo_cord_location_via_sample_event()` (+6 lines) |
| 246 | +
|
| 247 | +**Total Impact**: ~130 lines added (mostly comments + logging) |
| 248 | +
|
| 249 | +--- |
| 250 | +
|
| 251 | +## π¬ User Experience Flow |
| 252 | +
|
| 253 | +**Before**: |
| 254 | +1. User loads page |
| 255 | +2. *[5-10 seconds of frozen browser with "Loading..." text]* |
| 256 | +3. Globe appears with all points |
| 257 | +4. User clicks point |
| 258 | +5. *[1-2 seconds wait]* |
| 259 | +6. Tables appear |
| 260 | +
|
| 261 | +**After**: |
| 262 | +1. User loads page |
| 263 | +2. Globe appears immediately |
| 264 | +3. "Querying geocodes from parquet..." (2-8 sec) |
| 265 | +4. "Rendering geocodes... 500/1,234 (41%)" (0.4-0.8 sec, visible progress) |
| 266 | +5. All points visible, page interactive |
| 267 | +6. User clicks point |
| 268 | +7. *[1-2 seconds wait]* (console shows timing) |
| 269 | +8. Tables appear |
| 270 | +
|
| 271 | +**Key Difference**: User knows what's happening and page remains responsive! |
| 272 | +
|
| 273 | +--- |
| 274 | +
|
| 275 | +## π Additional Notes |
| 276 | +
|
| 277 | +- **No data model changes**: All optimizations are UX-level improvements |
| 278 | +- **No breaking changes**: Queries return same results, just with timing info |
| 279 | +- **No maintenance burden**: Once deployed, no ongoing work needed |
| 280 | +- **Fully backwards compatible**: Page works exactly the same, just feels faster |
| 281 | +- **Console logs can be removed**: If too noisy, delete console.log lines (keep timing code for future debugging) |
| 282 | +
|
| 283 | +--- |
| 284 | +
|
| 285 | +## β
Success Criteria |
| 286 | +
|
| 287 | +**Lazy Loading Implementation Complete When**: |
| 288 | +- β
Progress indicator shows during initial load |
| 289 | +- β
Page remains interactive during rendering |
| 290 | +- β
Console logs show timing measurements |
| 291 | +- β
No JavaScript errors in console |
| 292 | +- β
All points render correctly (same as before) |
| 293 | +- β
Click queries work with timing logs |
| 294 | +
|
| 295 | +**Ready for Next Phase When**: |
| 296 | +- Baseline metrics collected (query times, render times) |
| 297 | +- User feedback gathered (is it fast enough?) |
| 298 | +- Decision made: Phase 2 optimization needed? (Y/N) |
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