v0.5.1 = Initial rubyfb release To use rubyfb adapter in RoR set your database adpter to “rubyfb”

FireRuby Version 0.4.1

FireRuby is an extension for the Ruby programming language that provides access to the Firebird open source RDBMS. The FireRuby library is release under the Mozilla Public Licence version 1.1 and is free for commercial use.

Enhancements & Alterations

This release has been brought about as a direct result of efforts to get the library working on a 64 bit platform. This process exposed some code of questionable quality. All of the issues raised in getting a 64 bit build have been addressed and it’s only fair that the improvements obtained be passed on to all platforms. Functionally nothing has changed since the last release and the new version should replace the old with no problems.

Bug Fixes

A number of bug fixes were implemented as part of the effort to get the library working on a 64 bit platform. None of these had been raised as bugs against the library so I have nothing specific to tick off.

Backward Compatibility

Version 0.4.0 of the library made fundamental changes to functionality that was available in earlier versions of the library. To help accommodate this change elements were added to support backward compatibility. The relevant details are listed here…

  • Row objects were switched from keying on column names to keying on column aliases. To revert to the older functionality assign a value of true to the $FireRubySettings global setting.

  • DATE columns were switched from being returned as Time objects to be returned as Date objects. To revert to the older functionality assign a value of true to the $FireRubySettings global setting.

One other point to note is that, as of version 0.4.0, Enumerable is included in the Row and ResultSet classes.

Issues

Nothing is perfect so this section outlines those issues that are known to exist as of this release.

  • The service manager functionality does not appear to work on the Mac OS X platform. I don’t believe that this is a problem in the FireRuby code as I have tested the Firebird gbak utility with the -service option and it gives the same result. If anyone knows this to be untrue or of a work around let me know.

  • The library currently does not support array columns. This may be implemented for a later release depending on demand. No-one has asked for this so far so I’m starting to think that people don’t make much use of array columns.

  • The library can be a bit touchy if you don’t clean up after yourself. This can result in a segmentation violation whenever your program stops if you’ve left a ResultSet or Statement object unclosed. Check through your code to insure that this isn’t the case before contacting me about problems in this line.

  • The unit tests are currently set up on the assumption that the password for your sysdba account is ‘masterkey’. If this is not the case, or if you wish to use an alternative user for testing, edit the TestSetup.rb file in the unit test directory and update the entries there as appropriate. I should also note that you may need to alter permissions on the test directory to run the actual unit tests on Linux/Unix.

Credit Where Credit Is Due

Over its lifetime the FireRuby library has benefitted from input provided by a number of individuals. This section acknowledges these inputs…

Ken Kunz: Ken has been a strong supporter of the library from early on and has contributed through feedback, testing and suggestions. For some time he produced and tested the Linux builds of the library.

David Walthour: David basically executed all of the work to generate the 64 bit version of the library, along the way exposing some flaws in the code (amazing what a bit of peer review can find!). David produced the 64 bit version of the library gem.

John Wood: John currently builds and tests the Mac OS X version of the library.

Art Federov: Art provided input on handling and testing character sets.

Installation & Usage

The library is provided as a gem and built for use with Ruby 1.8+. Testing against an earlier release of Ruby has not been performed. Installation requires the Ruby Gems package to be installed. Assuming that these installation criteria have been met the library can be installed on Windows by executing a command such as the following…

gem install fireruby-0.4.1-mswin32.gem

On the Mac OS X platform you may require super user privilege if your Ruby is installed to the default location (i.e. /usr/local/lib). In this case you can use the sudo command to make the installation like this…

sudo gem install fireruby-0.4.1-powerpc-darwin.gem

Once the gem installation is complete the FireRuby functionality can be accessed in code with the usual gem style requires…

require 'rubygems'
require 'fireruby'

Build Details

The FireRuby library is a Ruby extension written in C. The avoid build issues binary versions are provided for a number of platforms, including…

  • Windows: Built against a version of Ruby installed using the one-click installer and using the freely available Microsoft development tools. This version was compiled against version 1.5.2 of Firebird.

  • Linux: Built on Ubuntu Linux (Breezy Badger) using a version of Ruby 1.8.2 installed via the Synaptic package manager. This package manager was also used to make an installation of Firebird.

  • Mac OS X: Build on version 10.4.3 of OS X against the 1.8.2 version of Ruby that comes with the operating system. A framework installation of Firebird version 1.5.1 was used to make the build.

Its possible to try and build the library on other platforms so I’ll provide a few details as to how to go about doing this. The first step is to download the CVS tar ball from the Ruby Forge site and expand it into a local directory. This will create a directory called fireruby. Change into this directory and then into the fireruby/src subdirectory.

This directory contains a file called extconf.rb that is used to create the make file used to build the library. The make file is created by executing this file but before you do there are a number of parameters that you should be aware of. The main one of these is –with-firebird-dir. This parameter is used to indicate the whereabouts of the Firebird headers and libraries. The following is an example of how this might be used…

ruby extconf.rb --with-firebird-dir=/usr/local/firebird

You may need to customise the path for your own Firebird installation. The path specified should be a directory that contains subdirectories called ‘lib’ and ‘include’. The lib subdirectory should contain the fbclient shared library and include should contain the ibase.h header file.

A note for Windows users. The library requires the free Microsoft C++ compiler, the Windows SDK, the .NET SDK and nmake to build. If you have all of these and Firebird installed to default locations then you can create a make file using the mkmf.bat batch file in the src directory.

Once you have the make file you can attempt a library build using either make (on Unix/Linux) or nmake (on Windows). If it builds successfully you can move on to creating a gem file for installation. To do this, change into the ../gem directory. In this directory you can do the following (on Windows)…

make_gem

…or the following (on Unix/Linux)…

ruby make_gem.rb

This will create the gem file in the main fireruby directory. Install this and execute the unit tests to check whether you’re version is working.

So How Do I Use It?

This section will provide some examples of usage for the the FireRuby classes. Throughout the code the following set of assumptions are made.

  • The user name and password that will be employed to attach to the database are ‘sysdba’ and ‘masterkey’ respectively (the Firebird defaults).

  • The databases attached to will all be local (i.e. they will all reside on the same machine) as the test code.

A database, from the Firebird perspective, is made up of one or more files. From a FireRuby perspective a user interaction with a database starts through the Database class. This class provides facilities that allow for creating, dropping and connecting to database instances. For example, to obtain a connection to a database you would use something like the following…

require 'rubygems'
require 'fireruby'
include FireRuby
db = Database.new('./test.fdb')
c  = db.connect('sysdba', 'masterkey')

This example starts by requiring the necessary files and including the FireRuby module locally - later examples will not detail these lines but they are always required to use the FireRuby code.

The first line of code after the include creates a new database object. This process does not actually create the database file (see the Database#create method API documentation if that is what you want to do), it simple creates an abstract reference to a database. In creating the Database object we had to provide a database specification string which identifies the database we want to access. In this case we are specifying a database in the current working directory called ‘test.fdb’. See the Firebird documentation for details on the structure of more complex database specifications.

The last line of code in the example given above opens a connection to the database. In doing this we had to provide two parameters, the database user name and password. These are required to gain access to the database.

A connection represents a conduit to a database and obtaining a connection is a prerequisite to working with the database. The FireRuby library support having multiple connections, to one or more databases, using one or more users, active simultaneously. FireRuby represents a database connection through objects of the Connection class. This class provides functionality to determine the current state a database connection (open or closed) and for closing the connection. Connections take up resources, both locally and on the database server and should be explicitly closed when they are no longer required.

The connection class also provides a set of conveniences methods to allow for the execution of SQL against a database. These methods, execute_immediate and execute, represently two slightly different approaches to executing SQL against the database. Refer to the API documentation for more information.

An advantage of using a relational database management system like Firebird is that it provides transactions. A transaction represents a block of work that is either all completed successful or none of it is applied. From the perspective of the database this means that a series of steps that make changes to the tables in the database can be wrapped in a transaction to insure that they either all complete or that none of the changes are applied.

The FireRuby library represents a database transaction through instances of the Transaction class. There are two ways of obtaining a Transaction using the library, both requiring you to have an open database connection. The first way is to construct a new Transaction object like so…

tx = Transaction.new(connection)

The Transaction constructor takes a single parameter which must be either a Connection object or an array of Connection objects. If you pass an array of Connection objects to this constructor then the Transaction created will apply across all of the databases that the connections refer to, allowing you to have transactional control of work that must utilise more than one database. The second way to obtain a transaction is to simply request one from a Connection object, like so.

tx = connection.start_transaction

In this case the transaction will only ever apply to one database, the one that the connection relates to. This method also accepts a block, taking a single parameter. The parameter passed to the block will be the transaction created. In this case the lifetime of the transaction is delimited by the block. If the block completes successfully then the work of the transaction will be committed to the database. If the block raises an exception then the transactional work will be rolled back.

When the block of work associated with a transaction is complete the user must instruct the system to either apply the changes implemented by the work or to discard them. This can be done by calling the commit or rollback methods of the Transaction class respectively. Once a transaction has been committed or rolled back it can no longer be used and should be discarded. Note that attempts to close a connection that has an active transaction against it will fail, so one of the commit or rollback methods should be explictly called in code. The block technique detailed above helps protect against the failure to do this and is a useful technique.

The Transaction object provides a number of other informational and utility methods. Check the API documentation for this class for more information.

So we’ve looked at connections and transactions, but how do we actually do something practical with the database. Well there are a number of possible approaches that we can take to this. Both the Connection and Transaction classes have convenience method for the execution of SQL statements and these are useful for quick SQL. Where you want something that you can repeatedly reuse and, optionally, pass parameters to then you need the Statement class.

The Statement class represents a SQL statement that has been validated and prepared for execution. Here’s an example of creating a SQL statement…

s = Statement.new(cxn, tx, 'SELECT * FROM MY_TABLE', 3)

In this example we have created a Statement object that wraps a SQL select from a table called MY_TABLE. The first parameter to the constructor is a Connection object and the second is a Transaction, both mandatory. You may be thinking ‘why do I need a transaction here, I’m not changing anything?‘. This is true (well sort of) but it’s a requirement of the underlying database system. This is also the case for the final parameter to the constructor. The value 3 is the SQL dialect to be used with the Statement. This exists for reason arising from the move from closed source Interbase to open source Firebird. The parameter should be given a value of between 1 and 3. If you’re not sure what this is and you’re only using Firebird it’s probably safe to use a value of 3 here. Other values are for backward compatibility. Consult the Firebird and Interbase documentation for more details.

Anyway, now that we have our Statement how do we use it? Well, the answer is that we call once of the Statement objects execute methods. The one to be called depends on whether the Statement requires parameters or not. What are parameters you ask? Well, look at the following…

s = Statement.new(cxn, tx, 'SELECT * FROM MY_TABLE WHERE MYID = ?', 3)

Note that the SQL select for this Statement contains a ‘?’. This is a position holder for a value that the statement expects to be provided later. A Statement that wraps such a piece of SQL must be provided with the necessary parameters to execute properly. Where a Statement object represents SQL that requires a parameter then the execute_for method must be called, like this…

s.execute_for([25])

This code executes the SQL substituting the parameters from the array of data passed to the function call. If a Statement object represents SQL that does not require parameter values a call to the execute method will suffice, such as the following…

s.execute

The execute methods for the Statement class, as with all of the execute methods for the FireRuby library, have three potential return values. They will either return an Integer, a ResultSet object or nil. A ResultSet object will only be returned for SQL statements that constitute a query, irrespective of whether that query returns any data. For all other SQL statements (inserts, updates and deletes) the execute method will return a count of the number of rows affected by the statement execution. For any other SQL statements the various execute methods will return nil.

A ResultSet object represents a handle by which the data retrieved for a SQL query can be accessed. While it’s possible to obtain a ResultSet from one of the execute methods on the Connection, Transaction or Statement classes it is more efficient to create one directly. The constructor for the ResultSet class accepts the same arguments as the constructor for the Statement class but will throw an exception if the SQL statement specified is not a query.

Once we have obtained a ResultSet we can extract the rows of data for a query from it. To fetch a row of data from a ResultSet object you call the fetch method, like the following…

row = r.fetch

This fetches a single row of data for a query represented as a Row object (which will be covered shortly). The ResultSet class also provides for iteration across the contents of a result set by providing an each method. The block to the each method will be passed the data for the ResultSet, a row at a time.

It should be noted that both the Statement and ResultSet objects hold resources while they are active. They both possess close methods and these should be explicitly called to release the associated resources. The exception to this rule is for ResultSets. If you select all of the rows from a ResultSet then the resources for the ResultSet are automatically released. It is still safe to call close on such a ResultSet as this will not cause errors.

Okay, so you’ve gotten a row of data in the form of a Row object from your ResultSet, how do we get the data out of it? Well, there are a number of ways of doing this. You can treat the Row object like an array and dereference the columns of data within the row like this…

value = row[1]

The index specified to the array dereference operator specifies the column that you want the data for. Column indices start at 0. Alternatively you can treat the Row object like a read only Hash object and use the column name to access the data, like this…

value = row['MYID']

This is beneficial as it frees you from the constraint of knowing the ordering of the columns within the row. For more information of the Row class please consult the API documentation.

That covers the bulk of the SQL classes provided by the FireRuby library. The two which haven’t been touched upon are the Generator class and the Blob class.

The Generator class is a wrapper around the Firebird generator facility. A generator, also known as a sequence, provides a means of creating a list of numeric values in a way that is guaranteed to be thread and process safe. Used properly generators can be employed to create unique sequences that make perfect table keys. Consult the API documentation for more details on the Generator class.

The Blob class is returned as part of the Row object data obtained from a ResultSet. The class wraps the concept of a binary large object stored in the database. Consult the API documentation for further information.

Errors

Whenever a problem occurs within a FireRuby library class then it is likely that a FireRubyException will be thrown. The FireRubyException class is the error class used by the FireRuby library whenever it hits trouble. The class provides a means of finding out a little more about what exactly has gone wrong. Again, consult the API documentation for more details.

Firebird Service Manager

The FireRuby library provides a set of class that provide for an interaction with the Firebird service manager. This interaction allows for the execution of tasks, such as the backing up of a database, on the database server. To execute such tasks against the service manager for a Firebird instance you first need to obtain a ServiceManager class instance. This can be done as follows…

sm = ServiceManager.new('localhost')

The constructor for the ServiceManager class takes a single parameter that is the host name of the server running the Firebird instance. In the example above this would be a local machine but could be any machine that can be reached over the network (NOTE: although Firebird supports a number of underlying transport protocols in accessing a service manager currently only TCP/IP is supported for the FireRuby library).

The next step in executing service manager tasks involves connecting your ServiceManager object to the service manager for a Firebird instance. To do this you must supply a user name and password. The user name and password used must be a user that exists on the Firebird instance. The user you connect as can affect the access to services that you receive. For example, to connect as the database administrator you might do the following…

sm.connect('sysdba', 'masterkey')

Assuming that this succeeds you are now ready to execute tasks through your ServiceManager object. Within the FireRuby library individual task are broken out into separate classes. For this release (0.4.1) there are four task classes provided in the library - Backup, Restore, AddUser and RemoveUser. I think the class names are relatively self explanatory but if you want more information consult the API documentation for a class.

To use the task classes you construct a class instance, configure it as you may need and then execute it. Here’s an example of going through this procedure to create a database backup…

b = Backup.new('c:\database\work.fdb', 'c:\temp\work.bak')
b.metadata_only = true
b.execute(sm)

The first list creates the new Backup object. The first parameter passed to this call is the path and name of the primary file of the database to be backed up (NOTE: All paths are relative to the database server). The second parameter is the path and name of the database backup file to be created. The second line sets an attribute on the class to indicate that only the metadata (i.e. it’s schema but not it’s data) for the specified database should be included in the backup. The final line begins the execution of the backup task on the database server. This will block until completion.

Its also possible to execute a batch of tasks against a service manager. To do this you would accumulate the tasks to be executed and then pass them all at the same time to the ServiceManager#execute method, like so…

t = Array.new
t.push(Backup.new('c:\database\work.fdb', 'c:\temp\work.bak'))
...
# Create more tasks here and add them to the array.
sm.execute(*t)

The tasks will be executed in the order they are specified to the ServiceManager object. For the example above this would mean in the order they were added to the array. For more details on the ServiceManager class and the various task classes please consult the API documentation.