in reply to Reading HUGE file multiple times

Index the file in one pass; then use the index to seek the id/data directly:

#! perl -slw
use strict;

my %idx; ## Index the file
$idx{ <> } = tell( ARGV ), scalar <> until eof();

for ( 1 .. 1000 ) {
    my $id = getNextId( ... );
    seek ARGV, $idx{ $id };
    scalar <>; # discard id line (or verify)
    print scalar <>; ## access data;
}

[download]

Untested code for flavour only.

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Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
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In the absence of evidence, opinion is indistinguishable from prejudice.

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Re^2: Reading HUGE file multiple times
by Anonymous Monk on Apr 28, 2013 at 10:35 UTC
    thanks, will try it right away
[reply]

      On my system, the code above indexed a 6.4 million record, 5GB file in 57 seconds. 

      1367141700
1367141757
6348909

      [download]

      Once indexed, accessing the records randomly runs at 1 second per thousand.

      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
[d/l]

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