Issue with the huge import script

[Devendra Jadhav <devendra.in@xxxxxxxxx>]

Hi,

I have to import data from one database to another, I have to import around
100000(1Lac) records.
First I need to check if the record is already imported or not and import
only those records which are not imported.

Here is my logic

$already_imported = get_already_imported_records();
format of the $already_imported is $already_imported[someid] = 'imported';

Now i take all records from another db and iterating through it.

if (!key_exists($already_imported[$new_id])){
        import_function($new_id)
}else{
        echo 'allready imported'.$already_imported[$new_id];
}

Now my script is importing same records for more than one time. I am not
able to get through this issue

Is it because of the size of the records or something else...?

Please suggest me some solution which is faster, safe and easy to code :D

Thanks in advance

-- 
Devendra Jadhav