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<title>KirbyBase Manual (Ruby Version)</title>
</head>
<body>
<div id="header">
<h1>KirbyBase Manual (Ruby Version)</h1>
<span id="author">Jamey Cribbs</span><br />
<span id="email"><tt><<a href="mailto:[email protected]">[email protected]</a>></tt></span><br />
v2.6 June 2006
</div>
<div id="preamble">
<div class="sectionbody">
<div class="imageblock">
<div class="content">
<img src="images/kirby1.jpg" alt="images/kirby1.jpg"/>
</div>
<div class="image-title">Figure: Kirby, pictured here in attack mode.</div>
</div>
</div>
</div>
<h2>Table of Contents</h2>
<div class="sectionbody">
<div class="sidebarblock">
<div class="sidebar-content">
<ol>
<li>
<p>
<a href="#introduction">Introduction</a>
</p>
</li>
<li>
<p>
<a href="#connecting-to-a-database">Connecting to a database</a>
</p>
</li>
<li>
<p>
<a href="#creating-a-new-table">Creating a new table</a>
</p>
<ol class="olist2">
<li>
<p>
<a href="#field-types">Database field types</a>
</p>
</li>
<li>
<p>
<a href="#recno">The recno field</a>
</p>
</li>
<li>
<p>
<a href="#encrypt">Turning on encryption</a>
</p>
</li>
<li>
<p>
<a href="#record-class">Specifying a custom record class</a>
</p>
</li>
<li>
<p>
<a href="#defaults">Specifying default values</a>
</p>
</li>
<li>
<p>
<a href="#requireds">Specifying required fields</a>
</p>
</li>
<li>
<p>
<a href="#creating-indexes">Indexes</a>
</p>
</li>
<li>
<p>
<a href="#a-note-about-indexes">A note about indexes</a>
</p>
</li>
<li>
<p>
<a href="#creating-lookup-fields">Lookup Fields</a>
</p>
</li>
<li>
<p>
<a href="#creating-link-many-fields">Link_many Fields</a>
</p>
</li>
<li>
<p>
<a href="#creating-calculated-fields">Calculated Fields</a>
</p>
</li>
</ol>
</li>
<li>
<p>
<a href="#obtaining-a-reference-to-an-existing-table">Obtaining a reference to an existing table</a>
</p>
</li>
<li>
<p>
<a href="#insert-method">The insert method</a>
</p>
</li>
<li>
<p>
<a href="#how-to-select-records">How to select records</a>
</p>
<ol class="olist2">
<li>
<p>
<a href="#select-method">The select method</a>
</p>
</li>
<li>
<p>
<a href="#selecting-by-index">Selecting by index</a>
</p>
</li>
<li>
<p>
<a href="#selecting-by-recno-index">Selecting by :recno index</a>
</p>
</li>
<li>
<p>
<a href="#selects-involving-lookups-or-link-manys">Selects involving Lookups or Link_manys</a>
</p>
</li>
<li>
<p>
<a href="#a-note-about-nil-values">A note about nil values</a>
</p>
</li>
</ol>
</li>
<li>
<p>
<a href="#kbresultset">KBResultSet</a>
</p>
<ol class="olist2">
<li>
<p>
<a href="#sorting-a-result-set">Sorting a result set</a>
</p>
</li>
<li>
<p>
<a href="#to-report">Producing a report from a result set</a>
</p>
</li>
<li>
<p>
<a href="#crosstabs">CrossTabs or Pivot Tables or Column Arrays (i.e. I don't know what to call them!)</a>
</p>
</li>
</ol>
</li>
<li>
<p>
<a href="#how-to-update-records">How to update records</a>
</p>
<ol class="olist2">
<li>
<p>
<a href="#update-method">The update method</a>
</p>
</li>
<li>
<p>
<a href="#set-method">The set method</a>
</p>
</li>
<li>
<p>
<a href="#update-all-method">The update_all method</a>
</p>
</li>
</ol>
</li>
<li>
<p>
<a href="#how-to-delete-records">How to delete records</a>
</p>
<ol class="olist2">
<li>
<p>
<a href="#delete-method">The delete method</a>
</p>
</li>
<li>
<p>
<a href="#clear-method">The clear method</a>
</p>
</li>
</ol>
</li>
<li>
<p>
<a href="#pack-method">The pack method</a>
</p>
</li>
<li>
<p>
<a href="#memo-and-blob-fields">Memo and Blob Fields</a>
</p>
</li>
<li>
<p>
<a href="#misc-kirbybase-methods">Miscellaneous KirbyBase methods</a>
</p>
<ol class="olist2">
<li>
<p>
<a href="#drop-table">KirbyBase#drop_table</a>
</p>
</li>
<li>
<p>
<a href="#tables">KirbyBase#tables</a>
</p>
</li>
<li>
<p>
<a href="#table-exists">KirbyBase#table_exists?</a>
</p>
</li>
<li>
<p>
<a href="#rename-table">KirbyBase#rename_table</a>
</p>
</li>
</ol>
</li>
<li>
<p>
<a href="#misc-kbtable-methods">Miscellaneous KBTable methods</a>
</p>
<ol class="olist2">
<li>
<p>
<a href="#update-by-recno">KBTable#[]=</a>
</p>
</li>
<li>
<p>
<a href="#get-by-recno">KBTable#[]</a>
</p>
</li>
<li>
<p>
<a href="#field-names">KBTable#field_names</a>
</p>
</li>
<li>
<p>
<a href="#field-types">KBTable#field_types</a>
</p>
</li>
<li>
<p>
<a href="#total-recs">KBTable#total_recs</a>
</p>
</li>
<li>
<p>
<a href="#import-csv">KBTable#import_csv</a>
</p>
</li>
<li>
<p>
<a href="#add-column">KBTable#add_column</a>
</p>
</li>
<li>
<p>
<a href="#drop-column">KBTable#drop_column</a>
</p>
</li>
<li>
<p>
<a href="#rename-column">KBTable#rename_column</a>
</p>
</li>
<li>
<p>
<a href="#change-column-type">KBTable#change_column_type</a>
</p>
</li>
<li>
<p>
<a href="#change-column-default-value">KBTable#change_column_defaul_value</a>
</p>
</li>
<li>
<p>
<a href="#change-column-required">KBTable#change_column_required</a>
</p>
</li>
<li>
<p>
<a href="#add-index">KBTable#add_index</a>
</p>
</li>
<li>
<p>
<a href="#drop-index">KBTable#drop_index</a>
</p>
</li>
</ol>
</li>
<li>
<p>
<a href="#special-characters-in-data">Special characters in data</a>
</p>
</li>
<li>
<p>
<a href="#table-structure">Table Structure</a>
</p>
</li>
<li>
<p>
<a href="#server-notes">Server Notes</a>
</p>
</li>
<li>
<p>
<a href="#tips-on-improving-performance">Tips on improving performance</a>
</p>
</li>
<li>
<p>
<a href="#single-user-diagram">Single-user memory space diagram</a>
</p>
</li>
<li>
<p>
<a href="#client-server-diagram">Client/Server memory space diagram</a>
</p>
</li>
<li>
<p>
<a href="#license">License</a>
</p>
</li>
<li>
<p>
<a href="#credits">Credits</a>
</p>
</li>
</ol>
</div></div>
</div>
<h2><a id="introduction"></a>Introduction</h2>
<div class="sectionbody">
<p>KirbyBase is a simple, pure-Ruby, flat-file database management system.
Some of its features include:</p>
<ul>
<li>
<p>
Since KirbyBase is written in Ruby, it runs anywhere that Ruby runs. It
is easy to distribute, since the entire DBMS is in one (approx. 100k) code
file.
</p>
</li>
<li>
<p>
All data is kept in plain-text, delimited files that can be edited by
hand. This gives you the ability to make changes by just opening the file
up in a text editor, or you can use another programming language to read the
file in and do things with it.
</p>
</li>
<li>
<p>
It can be used as an embedded database or in a client/server, multi-user
mode. To switch from one mode to the other, you only have to change one
line in your program. Included in the distribution is a sample database
server script using DRb.
</p>
</li>
<li>
<p>
Tables are kept on disk during use and accessed from disk when selecting,
updating, inserting, and deleting records. Changes to a table are written
immediately to disk. KirbyBase is not an "in-memory" database. Once you
update the database in your program, you can be assured that the change has
been saved to disk. The chance of lost data due to power interruptions, or
disk crashes is much reduced. Also, since the entire database does not have
to reside in memory at once, KirbyBase should run adequately on a
memory-constrained system.
</p>
</li>
<li>
<p>
You can specify the type of data that each field will hold. The available
data types are: String, Integer, Float, Boolean, Time, Date, DateTime, Memo,
Blob, and YAML.
</p>
</li>
<li>
<p>
The query syntax is very "rubyish". Instead of having to use another
language like SQL, you can express your query using Ruby code blocks.
</p>
</li>
<li>
<p>
All inserted records have an auto-incrementing primary key that is
guaranteed to uniquely identify the record throughout its lifetime.
</p>
</li>
<li>
<p>
You can specify that the result set be sorted on multiple fields, each
one either ascending or descending.
</p>
</li>
<li>
<p>
You can specify that certain fields be indexed. Using an index in a select
query can greatly improve performance on large tables (I've seen 10x speed
improvements). Index maintenance is completely handled by KirbyBase.
</p>
</li>
<li>
<p>
You can specify that a field has a "lookup table". Whenever that field is
accessed, the corresponding record from the lookup table is automatically
available.
</p>
</li>
<li>
<p>
You can specify one-to-many links between tables, somewhat analogous to a
"join" in SQL.
</p>
</li>
<li>
<p>
You can create calculated fields that are computed at runtime.
</p>
</li>
<li>
<p>
It is fairly fast, comparing favorably to SQLite.
</p>
</li>
</ul>
<p>In meeting your DBMS needs, KirbyBase fits in somewhere between plain
text files and small SQL database management systems like SQLite and
MySQL.</p>
<div class="sidebarblock">
<div class="sidebar-content">
<div class="sidebar-title">Drop me a line!</div>
<p>If you find a use for KirbyBase, please send me an email telling how you
use it, whether it is ok for me to mention your application on the
"KirbyBase Applications" webpage, and possibly a link to your application's
webpage (if you have one).</p>
</div></div>
</div>
<h2><a id="connecting-to-a-database"></a>Connecting to a database</h2>
<div class="sectionbody">
<p>To use Kirbybase, you first need to require the module:</p>
<div class="listingblock">
<div class="content">
<pre><tt>require 'kirbybase'</tt></pre>
</div></div>
<p>Then create an instance:</p>
<div class="listingblock">
<div class="content">
<pre><tt>db = KirbyBase.new</tt></pre>
</div></div>
<p>By default, the instance is a local connection using the same memory space
as your application. To specify a client/server connection, it would look
like this:</p>
<div class="listingblock">
<div class="content">
<pre><tt>db = KirbyBase.new(:client, 'localhost', 44444)</tt></pre>
</div></div>
<p>Of course, you would substitute your server's ip address and port number.</p>
<p>To specify a different location (other than the current directory) for the
database files, you need to pass the location as an argument, like so:</p>
<div class="listingblock">
<div class="content">
<pre><tt>db = KirbyBase.new(:local, nil, nil, './data')</tt></pre>
</div></div>
<p>KirbyBase treats every file in the specified directory that has the proper
extension as a database table. The default extension is ".tbl". To specify
a different extension, pass this as an argument, like so:</p>
<div class="listingblock">
<div class="content">
<pre><tt>db = KirbyBase.new(:local, nil, nil, './', '.dat')</tt></pre>
</div></div>
<p>To specify a different location other than the current directory for any
memo/blob files, you need to pass the location as an argument, like so:</p>
<div class="listingblock">
<div class="content">
<pre><tt>db = KirbyBase.new(:local, nil, nil, './', '.tbl', './memos')</tt></pre>
</div></div>
<p>If you don't want KirbyBase to spend time initially creating all of the
indexes for the tables in the database, you can pass true as the
delay_index_creation argument:</p>
<div class="listingblock">
<div class="content">
<pre><tt>db = KirbyBase.new(:local, nil, nil, './', '.tbl', './', true)</tt></pre>
</div></div>
<p>KirbyBase will skip initial index creation and will create a table's
indexes when the table is first referenced.</p>
<p>You can also specify the arguments via a code block. So, if you don't want
to have to specify a bunch of arguments just to get to the one you want,
put it in a code block attached to the method call. You could re-code the
previous example like so:</p>
<div class="listingblock">
<div class="content">
<pre><tt>db = KirbyBase.new { |d| d.delay_index_creation = true }</tt></pre>
</div></div>
</div>
<h2><a id="creating-a-new-table"></a>Creating a new table</h2>
<div class="sectionbody">
<p>To create a new table, you specify the table name, and a name and type for
each column. For example, to create a table containing information on World
War II planes:</p>
<div class="listingblock">
<div class="content">
<pre><tt>plane_tbl = db.create_table(:plane, :name, :String, :country, :String,
:role, :String, :speed, :Integer, :range, :Integer, :began_service, :Date,
:still_flying, :Boolean)</tt></pre>
</div></div>
<div class="sidebarblock">
<a id="field-types"></a>
<div class="sidebar-content">
<div class="sidebar-title">KirbyBase Field Types</div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/tip.png" alt="Tip" />
</td>
<td class="content">:String, :Integer, :Float, :Boolean(true/false), :Time, :Date,
:DateTime, :Memo, :Blob, and :YAML.</td>
</tr></table>
</div>
</div></div>
<div class="sidebarblock">
<a id="recno"></a>
<div class="sidebar-content">
<div class="sidebar-title">The recno field</div>
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/important.png" alt="Important" />
</td>
<td class="content">KirbyBase will automatically create a primary key field, called
recno, with a type of :Integer, for each table. This field will be
auto-incremented each time a record is inserted. You can use this field in
select, update, and delete queries, but you can't modify this field.</td>
</tr></table>
</div>
</div></div>
<h3><a id="encrypt"></a>Turning on encryption</h3>
<p>You can also specify whether the table should be encrypted. This will save
the table to disk encrypted (more like obfuscated) using a Vignere Cipher.
This is similar to rot13, but it uses a key to determine character
substitution. Still, this encryption will only stymie the most casual
of hackers. Do not rely on it to keep sensitive data safe! You specify
encryption by using a code block attached to #create_table:</p>
<div class="listingblock">
<div class="content">
<pre><tt>plane_tbl = db.create_table(:plane, :name, :String...) do |t|
t.encrypt = true
end</tt></pre>
</div></div>
<h3><a id="record-class"></a>Specifying a custom record class</h3>
<p>You can also specify that you want records of the table to be returned to
you as instances of a class. To do this, simply define a class before you
call #create_table. This class needs to have an accessor for each fieldname
in the table.</p>
<p>If this class has a class method, called #kb_create, KirbyBase, when
creating each record of the result set, will call that method and pass it
the field values of the result record. #kb_create will need to handle
creating an instance of the record class itself.</p>
<p>Here is an example of #kb_create in action:</p>
<div class="listingblock">
<div class="content">
<pre><tt>class Foobar
attr_accessor(:recno, :name, :country, :role, :speed, :range,
:began_service, :still_flying, :alpha, :beta)
def Foobar.kb_create(recno, name, country, role, speed, range,
began_service, still_flying)
name ||= 'No Name!'
speed ||= 0
began_service ||= Date.today
Foobar.new do |x|
x.recno = recno
x.name = name
x.country = country
x.role = role
x.speed = speed
x.range = range
x.began_service = began_service
x.still_flying = still_flying
end
end
def initialize(&block)
instance_eval(&block)
end
end</tt></pre>
</div></div>
<p>Pass this class to #create_table in an attached code block, like so:</p>
<div class="listingblock">
<div class="content">
<pre><tt>plane_tbl = db.create_table(:plane, :name, :String...) do |t|
t.record_class = Foobar
end</tt></pre>
</div></div>
<p>Now, when you call #select, the result set will be made up of instances of
Foobar, instead of the default, which is instances of Struct. This also
works the other way. You can now specify instances of Foobar as input to
the #insert, #update and #set methods. More on those methods below.</p>
<p>If the custom record class does not respond to #kb_create, KirbyBase will
call the class's #new method instead, passing it all of the field values.</p>
<div class="sidebarblock">
<div class="sidebar-content">
<div class="admonitionblock">
<table><tr>
<td class="icon">
<img src="./images/important.png" alt="Important" />
</td>
<td class="content">The #create_table method will return a reference to a KBTable
instance. This is the only way, besides calling KirbyBase#get_table, that
you can obtain a handle to a KBTable instance. You can not call KBTable#new
directly.</td>
</tr></table>
</div>
</div></div>
<h3>Specifying Advanced Field Type Information</h3>
<p>There are four types of advanced field type information that you can
specify:
Defaults, Requireds, Indexes and Extras (i.e. Lookup, Link_many,
Calculated).</p>
<h4><a id="defaults"></a>Default Field Values</h4>
<p>Normally, when you insert a record, if you don't specify a value for a field
or specify nil as the value, KirbyBase stores this as an empty string
(i.e. "") in the table's physical file, and returns it as a nil value when
you do a #select.</p>
<p>However, you can tell KirbyBase that you want a column to have a default
value. Only KBTable#insert is affected by default values. Default values
do not apply to updating a record. So, for inserts, there are two cases
where a default value, if one is specified, will be applied: (1) if nil
is specified for a field's value, and (2) if no value is specified for a
field.</p>
<p>For example, to specify that the category column has a default value, you
would code:</p>
<div class="listingblock">
<div class="content">
<pre><tt>db.create_table(:addressbook, :firstname, :String,
:lastname, :String, :phone_no, :String,
:category, {:DataType=>:String, :Default=>'Business'})</tt></pre>
</div></div>
<p>Notice that, since we are specifying advanced field type information, we
cannot just simply say :String for the second half of the field definition.
Instead, we have to pass a hash, with a :DataType item set to :String.
Next, because we are specifying a default value, we have to include a hash
item called :Default with its value set to whatever we want the default to
be. The default value must be of a type that is valid for the column.</p>
<h4><a id="requireds"></a>Required Fields</h4>
<p>Normally, when you insert or update a record, if you don't specify a value
for a field or specify nil as the value, KirbyBase stores this as an empty
string (i.e. "") in the table's physical file, and returns it as a nil
value when you do a #select.</p>
<p>However, you can tell KirbyBase that you want a column to be required
(i.e. you must supply a value and it can't be nil). When a record is
inserted or updated, an exception will be raised for any required field
that has not been given a value or been given a nil value.</p>
<p>For example, to specify that the category column is required, you would
code:</p>
<div class="listingblock">
<div class="content">
<pre><tt>db.create_table(:addressbook, :firstname, :String,
:lastname, :String, :phone_no, :String,
:category, {:DataType=>:String, :Required=>true})</tt></pre>
</div></div>
<p>Notice that, since we are specifying advanced field type information, we
cannot just simply say :String for the second half of the field definition.
Instead, we have to pass a hash, with a :DataType item set to :String.
Next, because we are specifying that a column is required, we have to
include a hash item called :Required with its value set to true.</p>
<h4><a id="creating-indexes"></a>Indexes</h4>
<p>Indexes are in-memory arrays that have an entry that corresponds to each
table record, but just holds the field values specified when the index was
created, plus the :recno of the actual table record. Because index arrays
are smaller than the actual table and because they are in-memory instead of
on-disk, using an index in a select query is usually much faster than
selecting against the table itself, especially when the table is quite
large.</p>
<p>To specify that an index is to be created, you need to tell KirbyBase which
fields are to be included in a particular index. You can have up to 5
indexes per table. Indexes can either contain single or multiple fields.
For example, to create an index on firstname and lastname for a table called
:addressbook, you would code:</p>
<div class="listingblock">
<div class="content">
<pre><tt>db.create_table(:addressbook, :firstname, {:DataType=>:String, :Index=>1},
:lastname, {:DataType=>:String, :Index=>1},
:phone_no, :String)</tt></pre>
</div></div>
<p>Notice that, since we are specifying advanced field type information, we
cannot just simply say :String for the second half of the field definition.
Instead, we have to pass a hash, with a :DataType item set to :String.
Next, because we are creating an index, we have to include a hash item
called :Index with its value set from 1 to 5. For compound indexes, like
the one in the above example, we need to make sure that all fields in the
index have the same number. To have another index for a table, just make
sure you increment the index number. So, for example, if we wanted to have
another index for the :addressbook table on the field phone number, we would
code:</p>
<div class="listingblock">
<div class="content">
<pre><tt>db.create_table(:addressbook, :firstname, {:DataType=>:String, :Index=>1},
:lastname, {:DataType=>:String, :Index=>1},
:phone_no, {:DataType=>:String, :Index=>2})</tt></pre>
</div></div>
<p>Notice how we just increment the index number to 2 for the :phone_no index.
Since there are no other fields with the same index number, this will create
an index with just the :phone_no field in it. You will see how to use
indexes in your select queries later.</p>
<div class="sidebarblock">
<a id="a-note-about-indexes"></a>
<div class="sidebar-content">
<div class="sidebar-title">A note about indexes</div>
<p>When KirbyBase initializes, it creates an instance for each table in
the database. It also creates each index array for each indexed field in
each table. So, if there are several large tables that have indexed fields,
this database initialization process could take several seconds. I decided
to have it operate this way, because I thought that it made more sense to
have a user application wait once upon initialization, rather than have it
wait the first time a table is referenced. A user is more used to waiting