Michael Schilli > Cache-Historical > Cache::Historical

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Module Version: 0.05   Source  

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>

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