Class: Og::Connection

Inherits:
Object show all
Defined in:
lib/og/connection.rb

Overview

A Connection to the Database. This file defines the skeleton functionality. A backend specific implementation file (driver) implements all methods.

Future

  • support caching.

  • support prepared statements.

Direct Known Subclasses

MysqlConnection, PsqlConnection, SqliteConnection

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(db) ⇒ Connection

Initialize a connection to the database.



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# File 'lib/og/connection.rb', line 36

def initialize(db)
	@db = db
	Logger.debug "Created DB connection." if $DBG 
end

Instance Attribute Details

#db ⇒ Object (readonly)

The Og database object.



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# File 'lib/og/connection.rb', line 24

def db
  @db
end

#store ⇒ Object

The actual connection to the backend store.



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# File 'lib/og/connection.rb', line 28

def store
  @store
end

Instance Method Details

#close ⇒ Object

Close the connection to the database.



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# File 'lib/og/connection.rb', line 43

def close
	@store.close
	Logger.debug "Closed DB connection." if $DBG
end

#commit ⇒ Object

Commit a transaction.



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# File 'lib/og/connection.rb', line 89

def commit
	exec 'COMMIT'
end

#count(sql, klass = nil) ⇒ Object

Perform a count query.



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# File 'lib/og/connection.rb', line 256

def count(sql, klass = nil)
	unless sql =~ /SELECT/i
		sql = "SELECT COUNT(*) FROM #{klass::DBTABLE} WHERE #{sql}"
	end
	
	res =	query(sql)
	return read_int(res)
end

#create_table(klass) ⇒ Object

Create the managed object table. The properties of the object are mapped to the table columns. Additional sql relations and constrains are created (indicices, sequences, etc).



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# File 'lib/og/connection.rb', line 52

def create_table(klass)
	raise 'Not implemented!'
end

#delete(obj_or_oid, klass = nil, cascade = true) ⇒ Object Also known as: delete!

Delete an object from the database. Allways perform a deep delete.

No need to optimize here with pregenerated code. Deletes are not used as much as reads or writes.

Input:

obj_or_oid = Object or oid to delete. klass = Class of object (can be nil if an object is passed)



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# File 'lib/og/connection.rb', line 275

def delete(obj_or_oid, klass = nil, cascade = true)
	oid = obj_or_oid.to_i
	klass = obj_or_oid.class unless klass

	# this is a class callback!
	
	if klass.respond_to?(:og_pre_delete)
		klass.og_pre_delete(self, oid)
	end
	
	# TODO: implement this as stored procedure? naaah.

	transaction do |tx|
		tx.exec "DELETE FROM #{klass::DBTABLE} WHERE oid=#{oid}"
		if cascade and klass.__meta.include?(:has)
			klass.__meta[:has].each do |dclass, linkback|
				tx.exec "DELETE FROM #{dclass::DBTABLE} WHERE #{linkback}=#{oid}"
			end
		end
	end
end

#drop_table(klass) ⇒ Object

Drop the managed object table.



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# File 'lib/og/connection.rb', line 58

def drop_table(klass)
	exec "DROP TABLE #{klass::DBTABLE}"
end

#exec(sql) ⇒ Object Also known as: execute

Execute an SQL query, no result returned.



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# File 'lib/og/connection.rb', line 76

def exec(sql)
	raise 'Not implemented!'
end

#insert(obj) ⇒ Object

Force insertion of managed object.



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# File 'lib/og/connection.rb', line 164

def insert(obj)
	obj.og_insert(self)
end

#load(oid, klass) ⇒ Object Also known as: get

Load an object from the database.

Input: oid = the object oid, OR the object name.



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# File 'lib/og/connection.rb', line 197

def load(oid, klass)
	if oid.to_i > 0 # a valid Fixnum ?
		load_by_oid(oid, klass)
	else
		load_by_name(oid, klass)
	end
end

#load_all(klass, extrasql = nil) ⇒ Object Also known as: get_all

Load all objects of the given klass. Used to be called ‘collect’ in an earlier version.



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# File 'lib/og/connection.rb', line 225

def load_all(klass, extrasql = nil)
	res = query "SELECT * FROM #{klass::DBTABLE} #{extrasql}"
	read_all(res, klass)
end

#load_by_name(name, klass) ⇒ Object Also known as: get_by_name

Load an object by name.



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# File 'lib/og/connection.rb', line 216

def load_by_name(name, klass)
	res = query "SELECT * FROM #{klass::DBTABLE} WHERE name='#{name}'"
	read_one(res, klass)
end

#load_by_oid(oid, klass) ⇒ Object Also known as: get_by_oid

Load an object by oid.



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# File 'lib/og/connection.rb', line 208

def load_by_oid(oid, klass)
	res = query "SELECT * FROM #{klass::DBTABLE} WHERE oid=#{oid}"
	read_one(res, klass)
end

#prepare(sql) ⇒ Object

Prepare an sql statement.



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# File 'lib/og/connection.rb', line 64

def prepare(sql)
	raise 'Not implemented!'		
end

#query(sql) ⇒ Object

Execute an SQL query and return the result.



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# File 'lib/og/connection.rb', line 70

def query(sql)
	raise 'Not implemented!'
end

#read_all(res, klass) ⇒ Object

Read (deserialize) all rows of the resultset.



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# File 'lib/og/connection.rb', line 133

def read_all(res, klass)
	raise 'Not implemented!'
end

#read_int(res, idx = 0) ⇒ Object

Read the first column of the resultset as an Integer.



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# File 'lib/og/connection.rb', line 139

def read_int(res, idx = 0)
	raise 'Not implemented!'
end

#read_one(res, klass) ⇒ Object

Read (deserialize) one row of the resultset.



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# File 'lib/og/connection.rb', line 127

def read_one(res, klass)
	raise 'Not implemented!'
end

#rollback ⇒ Object

Rollback a transaction.



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# File 'lib/og/connection.rb', line 95

def rollback
	exec 'ROLLBACK'
end

#save(obj) ⇒ Object Also known as: <<, put

Save an object to the database. Insert if this is a new object or update if this is already stored in the database.



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# File 'lib/og/connection.rb', line 150

def save(obj)
	if obj.oid
		# object allready inserted, update!
		obj.og_update(self)
	else
		# not in the database, insert!
		obj.og_insert(self)
	end
end

#select(sql, klass) ⇒ Object

Perform a standard SQL query to the database. Deserializes the results.



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# File 'lib/og/connection.rb', line 234

def select(sql, klass)
	unless sql =~ /SELECT/i
		sql = "SELECT * FROM #{klass::DBTABLE} WHERE #{sql}"
	end
	
	res = query(sql)
	read_all(res, klass)
end

#select_one(sql, klass) ⇒ Object

Optimized for one result.



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# File 'lib/og/connection.rb', line 245

def select_one(sql, klass)
	unless sql =~ /SELECT/i
		sql = "SELECT * FROM #{klass::DBTABLE} WHERE #{sql}"
	end
	
	res = query(sql)
	read_one(res, klass)
end

#start ⇒ Object

Start a new transaction.



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# File 'lib/og/connection.rb', line 83

def start
	exec 'START TRANSACTION'
end

#transaction(&block) ⇒ Object

Transaction helper. In the transaction block use the db pointer to the backend.



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# File 'lib/og/connection.rb', line 102

def transaction(&block)
	begin
		start
		yield(self) 
		commit
	rescue => ex
		Logger.error "DB Error: ERROR IN TRANSACTION"
		Logger.error "#{ex}"
		Logger.error "#{ex.backtrace}"
		rollback
	end
end

#update(obj) ⇒ Object

Force update of managed object.



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# File 'lib/og/connection.rb', line 170

def update(obj)
	obj.og_update(self)
end

#update_properties(update_sql, obj_or_oid, klass = nil) ⇒ Object Also known as: pupdate

Update only specific fields of the managed object.

Input: sql = the sql code to updated the properties.

WARNING: the object in memory is not updated. – TODO: should update the object in memory. ++



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# File 'lib/og/connection.rb', line 184

def update_properties(update_sql, obj_or_oid, klass = nil)
	oid = obj_or_oid.to_i
	klass = obj_or_oid.class unless klass
	
	exec "UPDATE #{klass::DBTABLE} SET #{update_sql} WHERE oid=#{oid}"
end

#valid_res?(res) ⇒ Boolean

Is the given resultset valid?

Returns:

  • (Boolean) 


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# File 'lib/og/connection.rb', line 121

def valid_res?(res)
	return !(res.nil?)
end