(podmaster) Re: In order traversal of BTREE keys where not all keys have duplicate values (using DB

What is the definition of your sub _compare?
(incomplete code cannot possibly demonstrate the problem)

~~Use the find_dup method to see if there are any duplicates.~~
(change the format of your values to help you out here, or just forget the whole R_DUP thing, and do something with the keys like some_key_part_1, some_key_part_2 ...)

Here is an example adapted from the DB_File documentation to show you a neat little trick

use strict ;
    use DB_File ;


    use vars qw( $x %h ) ;

    # Enable duplicate records
    $DB_BTREE->{'flags'} = R_DUP ;

    $x = tie %h, "DB_File", undef, O_RDWR|O_CREAT, 0640, $DB_BTREE 
        or die "Cannot open $filename: $!\n";

        $h{'Wall'} = 'only once';
        $h{'Smith'} = 'more than once';
        $h{'Smith'} = 'more than twice';
        $h{'Smith'} = 'three times';

    my $cnt  = $x->get_dup("Wall") ;
    print "Wall occurred $cnt times\n" ;
    my %hash = $x->get_dup("Wall", 1) ;
    print "Larry is there\n" if $hash{'Larry'} ;
    print "There are $hash{'Brick'} Brick Walls\n" ;
    my @list = sort $x->get_dup("Wall") ;
    print "Wall =>      [@list]\n" ;
    @list = $x->get_dup("Smith") ;
    print "Smith =>     [@list]\n" ;


    @list = $x->get_dup("Dog") ;
    print "Dog =>       [@list]\n" ;
[download]

particularly interesting is this tidbit



    $count = $x->get_dup($key) ;
    @list  = $x->get_dup($key) ;
    %list  = $x->get_dup($key, 1) ;
[download]

Look ma', I'm on CPAN.

** The Third rule of perl club is a statement of fact: pod is sexy.

Comment on (podmaster) Re: In order traversal of BTREE keys where not all keys have duplicate values (using DB_File) Select or Download Code

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Re: (podmaster) Re: In order traversal of BTREE keys where not all keys have duplicate values (using DB_File) by stajich (Chaplain) on May 20, 2002 at 15:19 UTC
Oops missing the compare function. `sub _compare { $_[0] <=> $_[1] }` Keys are numeric bins of the form 10000.000178 - this adapted from a mysql strategy where we are testing for bins within the boundaries but I am interested in an in-memory adaptation. I want to iterate through a subset of the keys that are bounded by some values $begin, $end not the whole set of keys as is demonstrated in all the examples. I was using get_dup to initialize the cursor and then iterate through all the available keys, however the cursor will only point to keys which have >1 value. === Ahem. I was making it harder than it should be. `$bhandle->seq($start,$v,R_CURSOR); while( $bhandle->seq($k,$v,R_NEXT) == 0 ) { last if( $k> $end); ... }` [download] Gets me what I want. Calling get_dup to initialize the cursor was not a smart idea and was the root of the problem.	[reply] [d/l] [select]

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Re: (podmaster) Re: In order traversal of BTREE keys where not all keys have duplicate values (using DB_File)
by stajich (Chaplain) on May 20, 2002 at 15:19 UTC

sub _compare { $_[0] <=> $_[1] }

Keys are numeric bins of the form 10000.000178 - this adapted from a mysql strategy where we are testing for bins within the boundaries but I am interested in an in-memory adaptation.

I want to iterate through a subset of the keys that are bounded by some values $begin, $end not the whole set of keys as is demonstrated in all the examples. I was using get_dup to initialize the cursor and then iterate through all the available keys, however the cursor will only point to keys which have >1 value.
===
Ahem. I was making it harder than it should be.

$bhandle->seq($start,$v,R_CURSOR);
while( $bhandle->seq($k,$v,R_NEXT) == 0 ) {
   last if( $k> $end);
   ...
}
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