freeing the memory used by a hash

[ravi]

which is a best way to free the all the memory used by a hash explain
in the context of complicated data structures like hash of hashes

undef %hash;
delete %hash;
%hash =();

What is the difference between these three

 

[Tore Aursand]

which is a best way to free the all the memory used by a hash explain in
the context of complicated data structures like hash of hashes

undef %hash;
delete %hash;
%hash =();

What is the difference between these three

What happened when you read the documentation, specifically:

perldoc -f undef
perldoc -f delete

You might also want to read these:

perldoc -q memory
perldoc -q shrinks

 

[Joe Smith]

which is a best way to free the all the memory used by a hash explain
in the context of complicated data structures like hash of hashes

undef %hash;
delete %hash;
%hash =();

The middle one is incomplete; the delete() function is used on
individual entries in the hash. To get them all, you would need
delete $hash{$_} for keys %hash;

All of them mark the memory used by the hash as being available for
reuse. Perl will use it for new variables when it needs it.
It will not return memory back to the OS.
-Joe

 

[Anno Siegel]

The middle one is incomplete; the delete() function is used on
individual entries in the hash. To get them all, you would need
delete $hash{$_} for keys %hash;

....or a slice:

delete @hash{ keys %hash};

Anno

 

[Tad McClellan]

which is a best way to free the all the memory used by a hash

Simply by letting the hash go out of scope.


{ my %hash;
# do stuff
}
# memory is reclaimed by perl here