# ANN: Sequel 0.2.1 Released

**URL:** <https://www.ruby-forum.com/t/ann-sequel-0-2-1-released/115477>\
**Category:** Ruby\
**Created:** [September 25, 2007, 5:43pm UTC](https://www.ruby-forum.com/t/ann-sequel-0-2-1-released/115477 "2007-09-25T17:43:59Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![ciconia](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/c/71c47a/32.png) [@ciconia](https://www.ruby-forum.com/u/ciconia)\
**Post date:** [September 25, 2007, 5:43pm UTC](https://www.ruby-forum.com/t/ann-sequel-0-2-1-released/115477/1 "2007-09-25T17:43:59Z")

</div>

Sequel version 0.2.1 has just been released. This release includes a  
number of major improvements, as well as many bug fixes.

Sequel is a lightweight ORM library for Ruby. Sequel provides thread  
safety, connection pooling and a simple and expressive API for  
constructing database queries and table schemas.

Following is a discussion of the major changes:

=== Dataset#query

In Sequel, dataset methods can be chained to express a query in a  
single line, but complex queries can be hard to read:

ds = DB[:txactions].select(:merchant\_id, :COUNT[:id] =\> :tx\_count).  
group\_by(:merchant\_id).order(:tx\_count.DESC).limit(5)

Dataset#query is a new method aimed at helping expressing complex  
queries:

ds = DB[:txactions].query do  
select :merchant\_id, :COUNT[:id] =\> :tx\_count  
group\_by :merchant\_id  
order :tx\_count.DESC  
limit 5  
end

You can also invoke the #query on databases:

ds = DB.query do  
from :items  
where {:x \> 1 && :y \< 2}  
end

=== Bang methods for mutating datasets

Also new are bang methods for manipulating datasets in place. Instead  
of doing this:

ds = DB[:items]  
ds = ds.filter(:active =\> true) if only\_active

You can now write:

ds = DB[:items]  
ds.filter!(:active =\> true) if only\_active

=== Dataset transforms

You can now specify automatic data transformations when retrieving and  
updating / inserting records. This feature is useful if you store  
serialized objects in the database. The Dataset#transform method takes  
a hash where each value is an array containing two proc objects. The  
first proc is used for retrieving records, and the second proc is used  
for updating / inserting records. The following example serializes  
objects using Marshal.

ds = DB[:items]  
ds.transform(:some\_column =\> [  
proc {|v| Marshal.load(v)},  
proc {|v| Marshal.dump(v)}  
])

ds.insert \<\< {:some\_column =\> [‘this is a Ruby array’]}  
ds.first #=\> {:some\_column =\> [‘this is a Ruby array’]}

=== More block filter goodness

Block filter behavior is now improved and more complete, adding  
support for strings with embedded Ruby expressions and ternary  
operators. You can reference variables, constants and virtually any  
Ruby object or expression in order to create parameterized queries.  
Here are some examples (from actual working code):

dataset.filter {:parent\_id =\> id}

dataset.filter {:path =~ /^#{path}/.+/}

dataset.filter {:stamp == ((Time.now - 86400 \* 3)…Time.now) && :kind  
== ALARM}

dataset.filter do  
:session\_id == producer ? producer\_id : consumer\_id  
:node\_id == Node.root.id  
end

You can put column references anywhere in your expressions:

dataset.filter {:price \> :AVG[:price]}  
#=\> “SELECT \* FROM items WHERE (price \> AVG(price))”

And since Sequel knows how to properly literalize any values you give  
it, you get protection from SQL injection for free!

=== Improved model classes

Sequel’s model class implementation is still a work in progress, but  
it is quite usable and includes the following new features:

- Model.serialize for specifying YAML/Marshal serialization/  
deserialization. This method uses Dataset#transform (mentioned above).  
Example usage:

In order to use Marshal serialization write the following:

serialize :value, :format =\> :marshal

- Support for composite primary keys. Example:

You can then find a record by specifying the session\_id and node\_id  
values:

ref = ProducerRef[sid, nid]

=== Bug fixes and miscellanea

- Fixed Dataset#insert\_sql to use DEFAULT VALUES clause if argument is  
an empty hash.

- Added Model#this method that provides the dataset filtered by the  
instance’s primary key.

- Added Model.no\_primary\_key method to allow models without primary  
keys.

- Added charset/encoding option to postgres adapter. Changed mysql  
adapter to support encoding option as well.

- Added support for case-sensitive regexps to mysql adapter.

- Fixed Symbol#to\_field\_name to support names with numbers and upper-  
case characters (#45).

- Added Dataset#empty? method (#46). This method returns true if the  
dataset contains no records.

- Added Dataset#order\_by as alias for Dataset#order, Dataset#group\_by  
as alias for Dataset#group.

- Improved Model#method\_missing to deal with invalid attributes.

- Added gem spec for Windows (without ParseTree dependency).

- Partially refactored model class and more model specs. Expect more  
in this department in the near future.

=== More info

Sequel project page:  
[http://code.google.com/p/ruby-sequel](http://code.google.com/p/ruby-sequel)

Sequel documentation:  
[http://sequel.rubyforge.org](http://sequel.rubyforge.org)

Join the Sequel-talk group:  
[http://groups.google.com/group/sequel-talk](http://groups.google.com/group/sequel-talk)

Install the gem:  
sudo gem install sequel

Or check out the source and install manually:  
svn co [http://ruby-sequel.googlecode.com/svn/trunk](http://ruby-sequel.googlecode.com/svn/trunk) sequel  
cd sequel  
rake install