backupccl: de-flake TestPaginatedBackupTenant

This test readily fails under stress with span configs enabled (cockroachdb#73876).
Now that we split within the tenant keyspace for tenant tables, the
export requests generated for each BACKUP is liable to be retried if
concurrent with range splits. The splits causes KV to error out with
RangeKeyMismatchErrors, at which point the request is internally
retried. The test, which wants to assert on what ExportSpan requests are
intercepted, previously did not need to consider these retries/need to
de-dup -- it now does.

Release note: None

pkg/ccl/backupccl/backup_test.go

@@ -767,7 +767,7 @@ func TestBackupRestoreAppend(t *testing.T) {
 
 		sqlDB.ExpectErr(t, "cannot append a backup of specific", "BACKUP system.users TO ($1, $2, "+
 			"$3)", test.backups...)
-		//TODO(dt): prevent backing up different targets to same collection?
+		// TODO(dt): prevent backing up different targets to same collection?
 
 		sqlDB.Exec(t, "DROP DATABASE data CASCADE")
 		sqlDB.Exec(t, "RESTORE DATABASE data FROM ($1, $2, $3)", test.backups...)
@@ -6793,6 +6793,8 @@ func TestPaginatedBackupTenant(t *testing.T) {
 	serverArgs := base.TestServerArgs{Knobs: base.TestingKnobs{JobsTestingKnobs: jobs.NewTestingKnobsWithShortIntervals()}}
 	params := base.TestClusterArgs{ServerArgs: serverArgs}
 	var numExportRequests int
+
+	exportRequestSpansSet := make(map[string]struct{})
 	exportRequestSpans := make([]string, 0)
 
 	requestSpanStr := func(span roachpb.Span, timestamp hlc.Timestamp) string {
@@ -6816,10 +6818,12 @@ func TestPaginatedBackupTenant(t *testing.T) {
 			for _, ru := range request.Requests {
 				if exportRequest, ok := ru.GetInner().(*roachpb.ExportRequest); ok &&
 					!isLeasingExportRequest(exportRequest) {
-					exportRequestSpans = append(
-						exportRequestSpans,
-						requestSpanStr(roachpb.Span{Key: exportRequest.Key, EndKey: exportRequest.EndKey}, exportRequest.ResumeKeyTS),
-					)
+					req := requestSpanStr(roachpb.Span{Key: exportRequest.Key, EndKey: exportRequest.EndKey}, exportRequest.ResumeKeyTS)
+					if _, found := exportRequestSpansSet[req]; found {
+						return nil // nothing to do
+					}
+					exportRequestSpansSet[req] = struct{}{}
+					exportRequestSpans = append(exportRequestSpans, req)
 					numExportRequests++
 				}
 			}
@@ -6847,6 +6851,7 @@ func TestPaginatedBackupTenant(t *testing.T) {
 
 	resetStateVars := func() {
 		numExportRequests = 0
+		exportRequestSpansSet = make(map[string]struct{})
 		exportRequestSpans = exportRequestSpans[:0]
 	}
 
@@ -6863,26 +6868,23 @@ func TestPaginatedBackupTenant(t *testing.T) {
 	systemDB.Exec(t, `SET CLUSTER SETTING kv.bulk_sst.max_allowed_overage='0b'`)
 
 	tenant10.Exec(t, `BACKUP DATABASE foo TO 'userfile://defaultdb.myfililes/test'`)
-	require.Equal(t, 1, numExportRequests)
 	startingSpan := roachpb.Span{Key: []byte("/Tenant/10/Table/56/1"), EndKey: []byte("/Tenant/10/Table/56/2")}
-	require.Equal(t, exportRequestSpans, []string{startingSpan.String()})
+	require.Equal(t, []string{startingSpan.String()}, exportRequestSpans)
 	resetStateVars()
 
 	// Two ExportRequests with one resume span.
 	systemDB.Exec(t, `SET CLUSTER SETTING kv.bulk_sst.target_size='50b'`)
 	tenant10.Exec(t, `BACKUP DATABASE foo TO 'userfile://defaultdb.myfililes/test2'`)
-	require.Equal(t, 2, numExportRequests)
 	startingSpan = roachpb.Span{Key: []byte("/Tenant/10/Table/56/1"),
 		EndKey: []byte("/Tenant/10/Table/56/2")}
 	resumeSpan := roachpb.Span{Key: []byte("/Tenant/10/Table/56/1/510/0"),
 		EndKey: []byte("/Tenant/10/Table/56/2")}
-	require.Equal(t, exportRequestSpans, []string{startingSpan.String(), resumeSpan.String()})
+	require.Equal(t, []string{startingSpan.String(), resumeSpan.String()}, exportRequestSpans)
 	resetStateVars()
 
 	// One ExportRequest for every KV.
 	systemDB.Exec(t, `SET CLUSTER SETTING kv.bulk_sst.target_size='10b'`)
 	tenant10.Exec(t, `BACKUP DATABASE foo TO 'userfile://defaultdb.myfililes/test3'`)
-	require.Equal(t, 5, numExportRequests)
 	var expected []string
 	for _, resume := range []exportResumePoint{
 		{[]byte("/Tenant/10/Table/56/1"), []byte("/Tenant/10/Table/56/2"), withoutTS},
@@ -8885,7 +8887,7 @@ DROP TABLE foo;
 }
 
 // TestRestoreNewDatabaseName tests the new_db_name optional feature for single database
-//restores, which allows the user to rename the database they intend to restore.
+// restores, which allows the user to rename the database they intend to restore.
 func TestRestoreNewDatabaseName(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	defer log.Scope(t).Close(t)