Add error handling for classification query failures

Wraps the color-coding classification query in try-catch to handle
intermittent DuckDB-WASM HTTP range request errors when querying
large remote parquet files.

Changes:
- Added try-catch around classification query execution
- Logs user-friendly error messages to console instead of crashing
- Page remains functional even if classification fails
- Provides helpful tips about retrying or using local cached file

Fixes occasional "Range request...offset is out of bounds" errors
that occur due to DuckDB-WASM limitations with remote files.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: rdhyee

tutorials/parquet_cesium.qmd

@@ -788,72 +788,86 @@ md`Retrieved ${pointdata.length} locations from ${parquet_path}.`;
         console.log("Classifying dots by type...");
         performance.mark('classify-start');
 
-        // Run the classification query
-        const query = `
-            WITH geo_classification AS (
+        try {
+            // Run the classification query
+            const query = `
+                WITH geo_classification AS (
+                    SELECT
+                        geo.pid,
+                        MAX(CASE WHEN e.p = 'sample_location' THEN 1 ELSE 0 END) as is_sample_location,
+                        MAX(CASE WHEN e.p = 'site_location' THEN 1 ELSE 0 END) as is_site_location
+                    FROM nodes geo
+                    JOIN nodes e ON (geo.row_id = e.o[1])
+                    WHERE geo.otype = 'GeospatialCoordLocation'
+                    GROUP BY geo.pid
+                )
                 SELECT
-                    geo.pid,
-                    MAX(CASE WHEN e.p = 'sample_location' THEN 1 ELSE 0 END) as is_sample_location,
-                    MAX(CASE WHEN e.p = 'site_location' THEN 1 ELSE 0 END) as is_site_location
-                FROM nodes geo
-                JOIN nodes e ON (geo.row_id = e.o[1])
-                WHERE geo.otype = 'GeospatialCoordLocation'
-                GROUP BY geo.pid
-            )
-            SELECT
-                pid,
-                CASE
-                    WHEN is_sample_location = 1 AND is_site_location = 1 THEN 'both'
-                    WHEN is_sample_location = 1 THEN 'sample_location_only'
-                    WHEN is_site_location = 1 THEN 'site_location_only'
-                END as location_type
-            FROM geo_classification
-        `;
-
-        const classifications = await db.query(query);
-
-        // Build lookup map: pid -> location_type
-        const typeMap = new Map();
-        for (const row of classifications) {
-            typeMap.set(row.pid, row.location_type);
-        }
+                    pid,
+                    CASE
+                        WHEN is_sample_location = 1 AND is_site_location = 1 THEN 'both'
+                        WHEN is_sample_location = 1 THEN 'sample_location_only'
+                        WHEN is_site_location = 1 THEN 'site_location_only'
+                    END as location_type
+                FROM geo_classification
+            `;
+
+            const classifications = await db.query(query);
+
+            // Build lookup map: pid -> location_type
+            const typeMap = new Map();
+            for (const row of classifications) {
+                typeMap.set(row.pid, row.location_type);
+            }
 
-        // Color and size styling by location type
-        const styles = {
-            sample_location_only: {
-                color: Cesium.Color.fromCssColorString('#2E86AB'),
-                size: 3
-            },  // Blue - field collection points
-            site_location_only: {
-                color: Cesium.Color.fromCssColorString('#A23B72'),
-                size: 6
-            },  // Purple - administrative markers
-            both: {
-                color: Cesium.Color.fromCssColorString('#F18F01'),
-                size: 5
-            }   // Orange - dual-purpose
-        };
-
-        // Update colors of existing points
-        const points = content.points;
-        for (let i = 0; i < points.length; i++) {
-            const point = points.get(i);
-            const pid = point.id;
-            const locationType = typeMap.get(pid);
-
-            if (locationType && styles[locationType]) {
-                point.color = styles[locationType].color;
-                point.pixelSize = styles[locationType].size;
+            // Color and size styling by location type
+            const styles = {
+                sample_location_only: {
+                    color: Cesium.Color.fromCssColorString('#2E86AB'),
+                    size: 3
+                },  // Blue - field collection points
+                site_location_only: {
+                    color: Cesium.Color.fromCssColorString('#A23B72'),
+                    size: 6
+                },  // Purple - administrative markers
+                both: {
+                    color: Cesium.Color.fromCssColorString('#F18F01'),
+                    size: 5
+                }   // Orange - dual-purpose
+            };
+
+            // Update colors of existing points
+            const points = content.points;
+            for (let i = 0; i < points.length; i++) {
+                const point = points.get(i);
+                const pid = point.id;
+                const locationType = typeMap.get(pid);
+
+                if (locationType && styles[locationType]) {
+                    point.color = styles[locationType].color;
+                    point.pixelSize = styles[locationType].size;
+                }
             }
-        }
 
-        performance.mark('classify-end');
-        performance.measure('classification', 'classify-start', 'classify-end');
-        const classifyTime = performance.getEntriesByName('classification')[0].duration;
-        console.log(`Classification completed in ${classifyTime.toFixed(0)}ms - updated ${points.length} points`);
-        console.log(`  - Blue (sample_location_only): field collection points`);
-        console.log(`  - Purple (site_location_only): administrative markers`);
-        console.log(`  - Orange (both): dual-purpose locations`);
+            performance.mark('classify-end');
+            performance.measure('classification', 'classify-start', 'classify-end');
+            const classifyTime = performance.getEntriesByName('classification')[0].duration;
+            console.log(`Classification completed in ${classifyTime.toFixed(0)}ms - updated ${points.length} points`);
+            console.log(`  - Blue (sample_location_only): field collection points`);
+            console.log(`  - Purple (site_location_only): administrative markers`);
+            console.log(`  - Orange (both): dual-purpose locations`);
+        } catch (error) {
+            console.error("Classification failed:", error);
+            console.error("Error details:", error.message);
+
+            // Show user-friendly message in browser console
+            console.warn("⚠️ Color-coding failed due to a data loading issue.");
+            console.warn("💡 Tip: This is an intermittent DuckDB-WASM issue with remote files.");
+            console.warn("    Try clicking the button again, or use a local cached file for better reliability.");
+            console.warn("    See the 'Using a local cached file' section above for instructions.");
+
+            // Note: We don't show an alert() to avoid disrupting the user experience
+            // The page remains functional, just without the color-coding
+        }
     }
 }
 ```