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Cache::Historical - Cache historical values

Historical(3pm) User Contributed Perl Documentation Historical(3pm)

NAME

Cache::Historical - Cache historical values

SYNOPSIS

    use Cache::Historical;
    my $cache = Cache::Historical->new();
 
       # Set a key's value on a specific date
    $cache->set( $dt, $key, $value );
       # Get a key's value on a specific date
    my $value = $cache->get( $dt, $key ); 
       # Same as 'get', but if we don't have a value at $dt, but we 
       # do have values for dates < $dt, return the previous 
       # historic value. 
    $cache->get_interpolated( $dt, $key );

DESCRIPTION

Cache::Historical caches historical values by key and date. If you have something like historical stock quotes, for example
    2008-01-02 msft 35.22
    2008-01-03 msft 35.37
    2008-01-04 msft 34.38
    2008-01-07 msft 34.61
then you can store them in Cache::Historical like
    my $cache = Cache::Historical->new();
    my $fmt = DateTime::Format::Strptime->new(
                  pattern => "%Y-%m-%d");
    $cache->set( $fmt->parse_datetime("2008-01-02"), "msft", 35.22 );
    $cache->set( $fmt->parse_datetime("2008-01-03"), "msft", 35.37 );
    $cache->set( $fmt->parse_datetime("2008-01-04"), "msft", 34.38 );
    $cache->set( $fmt->parse_datetime("2008-01-07"), "msft", 34.61 );
and retrieve them later by date:
    my $dt = $fmt->parse_datetime("2008-01-03");
      # Returns 35.37
    my $value = $cache->get( $dt, "msft" );
Even if there's no value available for a given date, but there are historical values that predate the requested date, "get_interpolated()" will return the next best historical value:
    my $dt = $fmt->parse_datetime("2008-01-06");
      # Returns undef, no value available for 2008-01-06
    my $value = $cache->get( $dt, "msft" );
      # Returns 34.48, the value for 2008-01-04, instead.
    $value = $cache->get_interpolated( $dt, "msft" );

Methods

new()
Creates the object. Takes the SQLite file to put the date into as an additional parameter:
 
    my $cache = Cache::Historical->new(
        sqlite_file => "/tmp/mydata.dat",
    );
    
 
The SQLite file defaults to
 
    $HOME/.cache-historical/cache-historical.dat
    
 
so if you have multiple caches, you need to use different SQLite files.
time_range()
       # List the time range for which we have values for $key
    my($from, $to) = $cache->time_range( $key );
    
keys()
       # List all keys
    my @keys = $cache->keys();
    
values()
       # List all the values we have for $key, sorted by date
       # ([$dt, $value], [$dt, $value], ...)
    my @results = $cache->values( $key );
    
clear()
       # Remove all values for a specific key
    $cache->clear( $key );
       # Clear the entire cache
    $cache->clear();
    
last_update()
       # Return a DateTime object of the last update of a given key
    my $when = $cache->last_update( $key );
    
since_last_update()
       # Return a DateTime::Duration object since the time of the last
       # update of a given key.
    my $since = $cache->since_last_update( $key );
    

LEGALESE

Copyright 2007-2011 by Mike Schilli, all rights reserved. This program is free software, you can redistribute it and/or modify it under the same terms as Perl itself.

AUTHOR

2007, Mike Schilli <cpan@perlmeister.com>
2011-04-27 perl v5.10.1