Handle CPU tracks having no slices (#33)

The CPU Slices track controller did not expect to see a CPU track having no slices whatsoever. The exception arising from processing the unexpected NULL in the query result resulted in subsequent attempts to set up the controller again and thus create the same view again. Signed-off-by: Christian W. Damus <[email protected]>
eclipsesource · Sep 13, 2023 · 9f0755f · 9f0755f
1 parent deb4203
commit 9f0755f
Showing 1 changed file with 10 additions and 2 deletions.
diff --git a/ui/src/tracks/cpu_slices/index.ts b/ui/src/tracks/cpu_slices/index.ts
@@ -23,7 +23,7 @@ import {
 } from '../../common/canvas_utils';
 import {colorForThread} from '../../common/colorizer';
 import {PluginContext} from '../../common/plugin_api';
-import {LONG, NUM} from '../../common/query_result';
+import {LONG, NUM, NUM_NULL} from '../../common/query_result';
 import {
   TPDuration,
   TPTime,
@@ -81,7 +81,15 @@ class CpuSliceTrackController extends TrackController<Config, Data> {
     const queryLastSlice = await this.query(`
     select max(id) as lastSliceId from ${this.tableName('sched')}
     `);
-    this.lastRowId = queryLastSlice.firstRow({lastSliceId: NUM}).lastSliceId;
+    const lastRowId = queryLastSlice.firstRow({lastSliceId: NUM_NULL})
+      .lastSliceId;
+    if (lastRowId === null) {
+      // There are no slices whatsoever to present.
+      this.lastRowId = -1;
+      this.maxDur = 0n;
+      return;
+    }
+    this.lastRowId = lastRowId;
 
     const row = queryRes.firstRow({maxDur: LONG, rowCount: NUM});
     this.maxDur = row.maxDur;