Question

I’m parsing a document and writing to disk pairs such as these ones:

0 vs 1, true
0 vs 2, false
0 vs 3, true
1 vs 2, true
1 vs 3, false
..

and so on.

Successively i’m balancing the trues and falses rows for each instance, by removing random lines (lines with true value if they exceed, and viceversa) and I end up with a file such as this one:

0 vs 1 true
0 vs 2 false
1 vs 2 true
1 vs 3 true
1 vs 4 false
1 vs 5 false

The falses are usually much much more than trues, so in the previous example, I could keep only 1 false for isntance 0, and only 2 falses for instance 1.

I’m doing this process in 2 steps, before parsing and then balancing.

Now, my issue is that the unbalanced file is too big: more than 1GB, and most of its rows are going to be removed by the balancing step.

My question is: can I balance the rows while parsing ?

My guess is no, because I don’t know which items are arriving and I can’t delete any row until when all rows for a specific instance have been discovered.

I hope it is clear.
thanks

Answer 1

What would happen if you used a lightweight database for this — derby, h2 etc? I imagine you can write sorting, filtering etc queries to arrive at what you want…