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>