# 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}, Name: #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}, Name: #'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 #janesjanes.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 #troubletrouble.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