From: Jeremy Evans <code@...>
Date: 2008-08-07T02:26:56+09:00
Subject: ANN: Sequel 2.4.0 Released

* Sequel provides thread safety, connection pooling and a concise DSL
  for constructing database queries and table schemas.
* Sequel also includes a lightweight but comprehensive ORM layer for
  mapping records to Ruby objects and handling associated records.
* Sequel supports advanced database features such as prepared
  statements, bound variables, master/slave configurations, and
  database sharding.
* Sequel makes it easy to deal with multiple records without having
  to break your teeth on SQL.
* Sequel currently has adapters for ADO, DB2, DBI, Informix, JDBC,
  MySQL, ODBC, OpenBase, Oracle, PostgreSQL and SQLite3.

Sequel 2.4.0 has been released and should be available on the gem
mirrors.  The 2.4.0 release focuses mainly on two major features:

Prepared Statements/Bound Variables
===================================

Sequel now supports prepared statements and bound variables.  No
matter which database you are using, Sequel uses exactly the same API.
To specify placeholders, you use the :$placeholder syntax:

  ds = DB[:items].filter(:name=>:$n)

To use a bound variable:

  ds.call(:select, :n=>'Jim')

This will do the equivalent of selecting records that have the name
'Jim'.  In addition to :select, you can use :first or :delete. There
is also support for bound variables when inserting or updating
records:

  ds.call(:update, {:n=>'Jim', :new_n=>'Bob'}, :name=>:$new_n)

Which will update all records that have the name 'Jim' to have the
name 'Bob'.

Prepared statement support is very similar to bound variable support,
except that the statement is first prepared with a name:

  ps = ds.prepare(:select, :select_by_name)

It is then called later with the bound arguments to use:

  ps.call(:n=>'Jim')
  DB.call(:select_by_name, :n=>'Jim') # same as above

For inserting or updating, the hash to use when inserting or updating
is given to prepare:

  ps2 = ds.prepare(:update, :update_name, :name=>:$new_n)
  ps2.call(:n=>'Jim', :new_n=>'Bob')

There is some level of native support for these features in the
PostgreSQL, MySQL, SQLite, and JDBC adapters.  For other adapters,
support is emulated, but it shouldn't be too difficult to add native
support for them.

For more details see:
http://sequel.rubyforge.org/rdoc/files/doc/prepared_statements_rdoc.html

Read-Only Slave/Writable Master and Database Sharding
=====================================================

Sequel now has built in support for master/slave database
configurations, just by setting an option in Sequel.connect:

  DB=Sequel.connect('postgres://master_server/database', \
    :servers=>{:read_only=>{:host=>'slave_server'}})

That will use slave_server for SELECT queries and master_server for
other queries.  It's fairly easy to use multiple slaves or even
multiple masters, examples are included in the link below.

Sharding support requires some code other than the database
configuration, but is still fairly simple.  For example, to set up
a 16 shard configuration based on a hex character:

  servers = {}
  (('0'..'9').to_a + ('a'..'f').to_a).each do |hex|
    servers[hex.to_sym] = {:host=>"hash_host_#{hex}"}
  end
  DB=Sequel.connect('postgres://hash_host/hashes', :servers=>servers)

To set which shard to use for a query, use the Dataset#server method:

  DB[:hashes].server(:a).filter(:hash=>/31337/)

For more details see:
http://sequel.rubyforge.org/rdoc/files/doc/sharding_rdoc.html

Other Changes
=============

* The sequel.rubyforge.org website has a new design thanks to boof.
  The online RDoc is now located at http://sequel.rubyforge.org/rdoc.

* Support was added for anonymous column names in the ADO adapter.

* Better MSSQL support in the ADO, ODBC, and JDBC adapters.  The
  odbc_mssql adapter has been removed. If you use MSSQL with ODBC,
  please use the odbc adapter with a :db_type=>'mssql' option.

* The following Sequel::Error exception subclasses were removed:
  InvalidExpression, InvalidFilter, InvalidJoinType, and WorkerStop.

* Documentation was added for the PostgreSQL, MySQL, SQLite, and
  JDBC adapters.

* Various internal interfaces were refactored.  For example, if you
  use an adapter not included with Sequel, it probably won't work
  until you update it to the new internal API.

* Many low level methods (such as Database#transaction), now take
  an optional server argument to indicate which server to use.

* Model plugins that have a DatasetMethods module with non-public
  methods no longer have Model methods created that call those
  methods.

If you have any questions, please post on the Google Group.

Thanks,
Jeremy

* {Website}[http://sequel.rubyforge.org]
* {Source code}[http://github.com/jeremyevans/sequel]
* {Bug tracking}[http://code.google.com/p/ruby-sequel/issues/list]
* {Google group}[http://groups.google.com/group/sequel-talk]
* {RDoc}[http://sequel.rubyforge.org/rdoc]
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