I have a script that builds a large data structure (a hash of records), and I notice that as the data set grows, it's beginning to slow down due to its large memory consumption. So now I'm trying to restrict the amount of memory it needs, by storing as minimal as necessary, and as compact as possible. The record structure is equivalent to: 
$record{$key} = { count => $integer, flag => $boolean }

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Populating the hash goes something like: 
foreach my $item (LARGE_LIST) {
    $key = property($item);
    $record{$key}{count}++;
    if(condition_is_true($item)) {
        $record{$key}{flag} = 1;
    }
}

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Later I'll be only interested to extract those keys for which the flag is set, and the count is 2 or more.

Now, how (and by how much) can I restrict the memory demands more? I think an array instead of a hash for the record structure could help a little, but probably not much.

I've also thought of using a string for the record and vec, but the equivalent of the above probably won't be this simple or as fast, for example, vec prefers that the string is defined — no depending on autovivification.

Any other ideas?

In reply to How to create a compact data structure? by bart

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