compare all data in database at same time ( real time) - real-time

Question

I have a problem with my android app, I have x value (whatever it is) and I have data in the database, I want to compare the value of x with all the data in the database at the same time in real time
the app is using sqlite.
I used a loop but when the database is large in this case my app lags in comparing all the data.my code is
public void Check_Distance(Location Current_Location,ArrayList<Location> LocationArrayList1)
{
double Distance;
for(int i=0;i<LocationArrayList1.size();i++)
{
Distance=distanceBetween(Current_Location,LocationArrayList1.get(i));
if(Distance<=0.1*1000){ // if distance is less then 100m give a sound
Notification_Sound();
}
}
}

Answer 1

You can't look at every record in the database at the exact same time. That's called quantum computing, and is currently an active research area where people far smarter than you or I are currently spending millions of dollars to try and create a machine that can do this kind of parallel processing.
That being said, you can make your algorithm more efficient, but that takes some effort to do. Both of the below are based on the idea of eliminating the majority of the locations that are obviously too far away very quickly, and performing more in-depth checks on those that could be in range.
One method is to sort the locations in ascending order in two arrays - one by North/South and the other by East/West. Find all entries within a given distance of the current position in each list, then combine the results to get a list of points within a box of X distance from the location. This box will have a much smaller number of points within it that you can then apply an iterative, circular, distance based approach to.
Another is to create a quadtree. This would subdivide the map area into a set of bounding volumes, where each volume would have a set of points, or additional bounding volumes. You can then place down your search area and find all the quadtree volumes that intersect with your circular search area, greatly minimizing the number of locations you need to do a true distance check on.