sql: fix panic in request_job_execution_details

This was fixed in  cockroachdb#106904
but it looks like some file movement in cockroachdb#105624 got rid of the nil check.
This patch re-adds the nil check along with a test, and also
some additional safeguards to not collect any execution details
for non-existent jobs.

Fixes: cockroachdb#106970
Release note: None

pkg/jobs/utils.go

@@ -140,3 +140,20 @@ ORDER BY created`
 	}
 	return false /* exists */, err
 }
+
+// JobExists returns true if there is a row corresponding to jobID in the
+// system.jobs table.
+func JobExists(ctx context.Context, jobID jobspb.JobID, db isql.DB) (bool, error) {
+	var exists bool
+	if err := db.Txn(ctx, func(ctx context.Context, txn isql.Txn) error {
+		row, err := txn.QueryRow(ctx, "check-for-job", txn.KV(), `SELECT id FROM system.jobs WHERE id = $1`, jobID)
+		if err != nil {
+			return err
+		}
+		exists = row != nil
+		return nil
+	}); err != nil {
+		return false, err
+	}
+	return exists, nil
+}

pkg/sql/jobs_profiler_execution_details.go

@@ -182,6 +182,15 @@ func (p *planner) RequestExecutionDetailFiles(ctx context.Context, jobID jobspb.
 	}
 
 	e := makeJobProfilerExecutionDetailsBuilder(execCfg.SQLStatusServer, execCfg.InternalDB, jobID)
+
+	// Check if the job exists otherwise we can bail early.
+	if exists, err := jobs.JobExists(ctx, jobID, e.db); err != nil {
+		return err
+	} else if !exists {
+		log.Warningf(ctx, "execution details requested for non-existent job %d", jobID)
+		return nil
+	}
+
 	// TODO(adityamaru): When we start collecting more information we can consider
 	// parallelize the collection of the various pieces.
 	e.addDistSQLDiagram(ctx)
@@ -238,7 +247,7 @@ func (e *executionDetailsBuilder) addDistSQLDiagram(ctx context.Context) {
 		log.Errorf(ctx, "failed to write DistSQL diagram for job %d: %+v", e.jobID, err.Error())
 		return
 	}
-	if row[0] != tree.DNull {
+	if row != nil && row[0] != tree.DNull {
 		dspDiagramURL := string(tree.MustBeDString(row[0]))
 		filename := fmt.Sprintf("distsql.%s.html", timeutil.Now().Format("20060102_150405.00"))
 		if err := jobs.WriteExecutionDetailFile(ctx, filename,

pkg/sql/jobs_profiler_execution_details_test.go

@@ -220,6 +220,10 @@ func TestReadWriteProfilerExecutionDetails(t *testing.T) {
 		require.True(t, strings.Contains(string(goroutines), fmt.Sprintf("labels: {\"foo\":\"bar\", \"job\":\"IMPORT id=%d\", \"n\":\"1\"}", importJobID)))
 		require.True(t, strings.Contains(string(goroutines), "github.com/cockroachdb/cockroach/pkg/sql_test.fakeExecResumer.Resume"))
 	})
+
+	t.Run("execution details for invalid job ID", func(t *testing.T) {
+		runner.Exec(t, `SELECT crdb_internal.request_job_execution_details(-123)`)
+	})
 }
 
 func TestListProfilerExecutionDetails(t *testing.T) {

pkg/sql/sem/builtins/builtins.go

@@ -7721,6 +7721,10 @@ specified store on the node it's run from. One of 'mvccGC', 'merge', 'split',
 					return nil, errors.New("must be admin to request a job profiler bundle")
 				}
 
+				if len(args) != 1 {
+					return nil, errors.New("argument list must have one element")
+				}
+
 				jobID := int(tree.MustBeDInt(args[0]))
 				if err := evalCtx.JobsProfiler.RequestExecutionDetailFiles(
 					ctx,