MatTableDataSource return a promise for ~ 7000 lines

I have a problem when try to put a lot of data in mattabledatasource, I want at least to display a loader but I don't know when data is already set. I try to use a promise like that :

return new Promise(resolve => {
this.infos.map(info => {
info.members.map(member => {
member.contacts.map(contact => {
dataSource.push({
contact,
member
});
});
});
});
this.dataSource = new MatTableDataSource(dataSource);
resolve();
});


But it is not working, just my table is freezing 10 seconds. How I can know when all maps + set data source is done ?

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