Struggling with filtering on an ngrx-store sourced MatTable

table-v1.ts

// I don't want to unwrap store observables, but looks like there is no other way

export class PageComponent {
  columnsToDisplay = ['firstName', 'lastName'];
  students$: Observable<Student[]>;
  studentsDataSource$: Observable<MatTableDataSource<Student>>;
  filterCtrl = new FormControl('');
    
  // this works, but performance-wise is doubtful  
  ngOnInit() {
    this.students$ = this.store.select(fromStudents.getStudents);

    this.studentsDataSource$ = combineLatest(
      this.filterCtrl.valueChanges,
      this.students$,
    ).pipe(
      map(([term, students]) => {
        const ds = new MatTableDataSource(students); // <-- this doesn't look efficient - you should onl
        ds.filter = term.toLowerCase();

        console.log(ds);
        return ds;
      })
    );
          
    this.store.dispatch(new studentsActions.LoadStudentsAction());
  }
          
          
  // this does not work          
  ngOnInit_v2 {
    this.students$ = this.store.select(fromStudents.getStudents);

    this.studentsDataSource$ = this.students$.pipe(
      map(students => new MatTableDataSource(students)),
    );

    this.filterCtrl.valueChanges.pipe(
      withLatestFrom(
        this.studentsDataSource$,
      ),
    ).subscribe(([term, ds]) => {
      ds.filter = term.toLowerCase();
    });       
  }
}

table.html

<mat-form-field>
 <input matInput type="text" #studentsFilter [formControl]="filterCtrl" placeholder="Filter">
</mat-form-field>

<mat-table [dataSource]="studentsDataSource$ | async" #studentsTable>
  <ng-container matColumnDef="firstName">
    <mat-header-cell *matHeaderCellDef>First Name</mat-header-cell>
    <mat-cell *matCellDef="let student">{{student.first_name}}</mat-cell>
  </ng-container>

  <ng-container matColumnDef="lastName">
    <mat-header-cell *matHeaderCellDef>Last Name</mat-header-cell>
    <mat-cell *matCellDef="let student">{{student.last_name}}</mat-cell>
  </ng-container>
  
  <mat-header-row *matHeaderRowDef="columnsToDisplay; sticky: true"></mat-header-row>
  <mat-row *matRowDef="let row; columns: columnsToDisplay"></mat-row>
</mat-table>