isidrolv / fb

Firebird Extension Library for Ruby

Ruby Firebird Extension Library

Please see the RDoc documentation for API details.

What follows is a brief overview of how to use this library.

This file is executable. However, you may have to adjust the database connection parameters.

Load the library

require 'fb'

The library contains on module, Fb.

Within Fb are four primary classes, Fb::Database, Fb::Connection, Fb::Cursor and Fb::Error.

For convenience, we'll include these classes into the current context.

include Fb

The Database class acts as a factory for Connections.

It can also create and drop databases.

db = Database.new( :database => "localhost:c:/var/fbdata/readme.fdb", :username => 'sysdba', :password => 'masterkey')

:database is the only parameter without a default.

Let's connect to the database, creating it if it doesn't already exist.

conn = db.connect rescue db.create.connect

We'll need to create the database schema if this is a new database.

conn.execute("CREATE TABLE TEST (ID INT NOT NULL PRIMARY KEY, NAME VARCHAR(20))") if !conn.table_names.include?("TEST")

Let's insert some test data using a parameterized query. Note the use of question marks for place holders.

10.times {|id| conn.execute("INSERT INTO TEST VALUES (?, ?)", id, "John #{id}") }

Here we'll conduct a spot check of the data we have just inserted.

ary = conn.query("SELECT * FROM TEST WHERE ID = 0 OR ID = 9") ary.each {|row| puts "ID: #{row[0]}, Name: #{row[1]}" }

Don't like tying yourself down to column offsets?

ary = conn.query(:hash, "SELECT * FROM TEST WHERE ID = 0 OR ID = 9") ary.each {|row| puts "ID: #{row['ID']}, Name: #{row['NAME']}" }

Let's change all the names.

total_updated = 0 conn.execute("SELECT ID FROM TEST") do |cursor| cursor.each do |row| updated = conn.execute("UPDATE TEST SET NAME = ? WHERE ID = ?", "John Doe #{row[0]}", row[0]) total_updated += updated end end puts "We updated a total of #{total_updated} rows."

Actually, I only need the first and last rows.

deleted = conn.execute("DELETE FROM TEST WHERE ID > ? AND ID < ?", 0, 9) puts "Expecting to delete 8 rows, we have deleted #{deleted}."

Using a simple, per-connection transaction strategy, we'll demonstrate rollback and commit.

conn.transaction

for i in 10..1000 conn.execute("INSERT INTO TEST VALUES (?, ?)", i, "Jane #{i}") end

What was I thinking? Let's roll that back.

conn.rollback

Are they still there?

janes = conn.query("SELECT * FROM TEST WHERE ID >= 10") puts "Expecting zero rows, we find #{janes.size} Janes."

Let's try again.

conn.transaction

10.upto(19) do |i| conn.execute("INSERT INTO TEST (ID, NAME) VALUES (?, ?)", i, "Sue #{i}") end

That's more like it.

conn.commit

It's important to close your cursor when you're done with it.

cursor = conn.execute("SELECT * FROM TEST") while row = cursor.fetch(:hash) break if row['NAME'] =~ /e 13/ end cursor.close

You may find it easier to use a block.

conn.execute("SELECT * FROM TEST") do |cursor| while row = cursor.fetch(:hash) break if row['NAME'] =~ /e 13/ end end

That way the cursor always gets closed, even if an exception is raised.

Transactions work the same way. Here's one that should work.

conn.transaction do 20.upto(25) do |i| conn.execute("INSERT INTO TEST VALUES (?, ?)", i, "George #{i}") end end

The transaction is automatically committed if no exception is raised in the block.

We expect trouble in this next example, on account of our primary key.

begin conn.transaction do execute("INSERT INTO TEST VALUES (0, 'Trouble')") puts "This line should never be executed." end rescue puts "Rescued." end

Is it there?

trouble = conn.query("SELECT * FROM TEST WHERE NAME = 'Trouble'") puts "Expecting zero rows, we find #{trouble.size} 'Trouble' rows."

How about demonstrating a more advanced transaction?

First, we'll start a snapshot transaction.

This should give us a consistent view of the database.

conn.transaction("SNAPSHOT") do

Then, we'll open another connection to the database and insert some rows.

Database.connect(:database => "localhost:c:/var/fbdata/readme.fdb") do |conn2| for i in 100...110 conn2.execute("INSERT INTO TEST VALUES (?, ?)", i, "Hi #{i}") end end

Now, let's see if we see them.

hi = conn.query("SELECT * FROM TEST WHERE ID >= ?", 100) puts "Expecting zero rows, we find #{hi.size} Hi rows." end

Now we will try our example again, only with a READ COMMITTED transaction.

conn.transaction("READ COMMITTED") do

Then, we'll open another connection to the database and insert some rows.

Database.connect(:database => "localhost:c:/var/fbdata/readme.fdb") do |conn2| for i in 200...210 conn2.execute("INSERT INTO TEST VALUES (?, ?)", i, "Hello #{i}") end end

Now, let's see if we see them.

hello = conn.query("SELECT * FROM TEST WHERE ID >= ?", 200) puts "Expecting ten rows, we find #{hello.size}." end

Don't forget to close up shop.

conn.close

We could have called conn.drop.

We could still call db.drop