in reply to Re^6: Reading HUGE file multiple times
in thread Reading HUGE file multiple times
Problem is there is an error with tell and it's all -1.
D'oh! I made the same mistake you did; I forgot to change ARGV for $Library. The line should read:
$Library_Index{<$Library>} = tell($library), scalar <$Library> until e +of($Library);
I tested the write-the-index-to-disc code with a file containing 17,000 id/record pairs with 300,000 data records (5.2GB).
This creates the index and writes it to disc:
#! perl -slw use strict; use Storable qw[ store ]; print time; my %idx; $idx{ <> } = tell( STDIN ), scalar <> until eof STDIN; store \%idx, '1031021.idx' or die $!; print time;
The whole process takes a little over 3 minutes:
C:\test>1031021-i.pl <1031021.dat 1367160156 1367160362 C:\test>dir 1031021* 28/04/2013 15:30 193 1031021-i.pl 28/04/2013 15:04 5,272,940,608 1031021.dat 28/04/2013 15:46 316,385 1031021.idx 28/04/2013 15:29 374 1031021.pl
And this code loads that index from disk (<1 second) and the reads 1000 random records (26 seconds) using it:
#! perl -slw use strict; use Storable qw[ retrieve ]; print time; my $idx = retrieve '1031021.idx' or die $!; print time; open DAT, '+<', '1031021.dat' or die $!; for( 1 .. 1000 ) { my( $id, $offset ) = each %$idx; seek DAT, $offset, 0; my $vid = <DAT>; die 'mismatch' unless $id eq $vid; my $data = <DAT>; } close DAT; print time;
Run:
C:\test>1031021.pl 1367160624 1367160624 1367160651
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Re^8: Reading HUGE file multiple times
by Anonymous Monk on Apr 28, 2013 at 20:03 UTC |
In Section
Seekers of Perl Wisdom