NAME
Database::Abstraction - database abstraction layer
VERSION
Version 0.10
SYNOPSIS
Abstract class giving read-only access to CSV, XML and SQLite databases via Perl without writing any SQL. Look for databases in $directory in this order: 1) SQLite (file ends with .sql) 2) PSV (pipe separated file, file ends with .psv) 3) CSV (file ends with .csv or .db, can be gzipped) (note the default sep_char is '!' not ',') 4) XML (file ends with .xml)
For example, you can access the files in /var/db/foo.csv via this class:
package MyPackageName::Database::Foo;
use Database::Abstraction;
our @ISA = ('Database::Abstraction');You can then access the data using:
my $foo = MyPackageName::Database::Foo->new(directory => '/var/db');
print 'Customer name ', $foo->name(customer_id => 'plugh'), "\n";
my $row = $foo->fetchrow_hashref(customer_id => 'xyzzy');
print Data::Dumper->new([$row])->Dump();If the table has a column called "entry", entries are keyed on that and sorts are based on it. To turn that off, pass 'no_entry' to the constructor, for legacy reasons it's enabled by default.
# Regular CSV: There is no entry column and the separators are commas
sub new
{
my $class = shift;
my %args = (ref($_[0]) eq 'HASH') ? %{$_[0]} : @_;
return $class->SUPER::new(no_entry => 1, sep_char => ',', %args);
}CSV files that are not no_entry can have empty lines or comment lines starting with '#', to make them more readable.
SUBROUTINES/METHODS
init
Set some class level defaults.
MyPackageName::Database::init(directory => '../data');See the documentation for new to see what variables can be set.
Returns a reference to a hash of the current values. Therefore when given with no arguments you can get the current default values:
my $defaults = Database::Abstraction::init();
print $defaults->{'directory'}, "\n";new
Create an object to point to a read-only database.
Arguments:
cache => place to store results; cache_duration => how long to store results in the cache (default is 1 hour); directory => where the database file is held max_slurp_size => CSV/PSV files smaller than this are held in RAM (default is 16K)
If the arguments are not set, tries to take from class level defaults.
set_logger
Pass a class that will be used for logging.
selectall_hashref
Returns a reference to an array of hash references of all the data meeting the given criteria.
Note that since this returns an array ref, optimisations such as "LIMIT 1" will not be used.
selectall_hash
Returns an array of hash references
fetchrow_hashref
Returns a hash reference for one row in a table. Special argument: table: determines the table to read from if not the default, which is worked out from the class name
execute
Execute the given SQL on the data. In an array context, returns an array of hash refs, in a scalar context returns a hash of the first row
On CSV tables without no_entry, it may help to add "WHERE entry IS NOT NULL AND entry NOT LIKE '#%'" to the query.
updated
Time that the database was last updated
AUTOLOAD
Return the contents of an arbitrary column in the database which match the given criteria Returns an array of the matches, or only the first when called in scalar context
If the database has a column called "entry" you can do a quick lookup with
my $value = $foo->column('123'); # where "column" is the value you're afterSet distinct or unique to 1 if you're after a unique list.
AUTHOR
Nigel Horne, <njh at bandsman.co.uk>
BUGS
The default delimiter for CSV files is set to '!', not ',' for historical reasons. I really ought to fix that.
It would be nice for the key column to be called key, not entry, however key's a reserved word in SQL.
LICENSE AND COPYRIGHT
Copyright 2015-2024 Nigel Horne.
This program is released under the following licence: GPL2. Usage is subject to licence terms. The licence terms of this software are as follows: Personal single user, single computer use: GPL2 All other users (for example Commercial, Charity, Educational, Government) must apply in writing for a licence for use from Nigel Horne at the above e-mail.