If parts of your application (DB, EXEs, etc.) are taking seconds or milliseconds to run,
spending time optimising map to save a few micro- or nanoseconds is unlikely to be worth the effort.
Another consideration is whether this is a short-lived application that's run multiple times
or a long-lived application that's run with multiple iterations.
There are some JIT (just-in-time) possibilities that may be worth consideration.
If you end up with a lot of get_X_for_Y() subs,
and some are only called infrequently,
you can create mappings just when they're needed; something like this using
state (which requires v5.10):
{
my %dat_by_id = ...;
sub get_X_for_Y {
my ($Y) = @_;
state $map_Y_to_id = {
map +($_->{Y} => $_->{id}), values %dat_by_id
};
return $dat_by_id{$map_Y_to_id->{$Y}}{X};
}
sub get_X_for_Z { ... }
sub get_V_for_W { ... }
...
}
Note that the anonymous block gives %dat_by_id lexical scope such that it is only visible to the subs;
while the subs themselves are visible to, and accessible from, the entire script.
This prevents inadvertent changes to %dat_by_id which could introduce bugs which are hard to track down.
Also note that the placement of the above code within your script would be important.
The assignment to %dat_by_id should occur before any calls to get_?_for_?() are made.
An alternative to this would be to use some combination of BEGIN, INIT, etc. blocks;
I don't know enough about your code to comment further on this; see
perlmod: BEGIN, UNITCHECK, CHECK, INIT and END
for more about these.
There would, no doubt, be other ways to handle this but, as previously stated,
I don't know enough about your code to offer further advice.
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