- Dec 28, 2001
- What Is the ZODB?
- Relational Database Management Systems (RDBMS)
- Why Are Database Adapters Necessary?
- Which Database Adapter Do I Need?
- Connecting MySQL and Zope
- Gadfly—Zope's Integrated Demo Relational Database
- Introduction to SQL
- Using Z SQL Methods to Submit SQL Statements
GadflyZope's Integrated Demo Relational Database
Gadfly is a simple RDBMS that comes with Zope. Its features and possibilities cannot compete with any of the previously mentioned RDBMSs, but it is sufficient for testing purposes. This RDBMS is written entirely in Python and supports the basic RDBMS Structured Query Language (SQL).
Gadfly can be run on any machine where Python is installed and is independent from the platform on which you are working. That allows you to copy the Gadfly directory via a binary stream from a Windows machine to a Linux machine.
Because Gadfly supports log-based recovery protocols, you can recover actions made in the database even if the database was not shut down properly.
Establishing a Gadfly Database Connection
Before you can use the Gadfly database, a database connection needs to be established. This is done by creating an instance of the database adapter in Zope.
To create an instance of the Gadfly Database Connection, choose Z Gadfly Database Connection from the drop-down menu in the Zope Management screen. Your browser will automatically be directed to the page shown in Figure 3.2.
Figure 3.2 Add a Z Gadfly Database Connection.
Fill out the form with the following data:
|Title:||Demo Z Gadfly Database|
Now, select Demo from the list of data sources, make sure the box to the right of Connect Immediately? is checked, and press the Add button. The database connection is created and the connection to the database is automatically opened. Your browser is now directed back to the Content view of your root folder where you can see the new instance of the database connection, as shown in Figure 3.3.
Figure 3.3 The instance of the Z Gadfly Database Connection.
Whenever you create objects in Zope, you have to give the object an ID. This ID cannot contain spaces or special characters that are invalid in URLs because the ID is used as an URL to the respective object. You need not choose a title for a new object, but it sometimes makes it easier to have a short description for a title.
The Different Views of the Database Connection
If you click MyGadflyDatabaseConnection, you are directed to the Status View of the database connection. This is the default view for this type of object.
This view shows you the status of the respective database connection. For example, it tells you whether the database connection is open or closed, as seen in Figure 3.4. You can also change that status by clicking Close Connection or Open Connection. The name of the button changes depending on the status of the connection.
The Properties View (see Figure 3.5) allows you to change the properties of the database connection. The properties include the title, the source for the connection, and whether the connection is to be established immediately.
You can use one instance of the Z Gadfly Database Connection to connect to different databases, but only one database at a time. If you want to create a new database called something other than Demo, see the "How to Create Different Z Gadfly Databases" section later in this chapter.
Figure 3.4 Status View of the database connection.
Figure 3.5 Properties View of the database connection.
This view allows you to test SQL statements. Enter the SQL query in the text area and click the Submit Query button (see Figure 3.6). The query will be sent to the database and executed. In this way, you can test SQL statements without creating Z SQL methods.
Figure 3.6 Test View of the database connection.
Figure 3.7 shows the result of your queryif there is any. Below the result, the view shows the statement used.
The Security View (see Figure 3.8) exists in most objects in Zope. It is used to create new roles or change the permission settings for the existing roles. It also contains a link to another page where local roles can be set. The list of permissions depend on whether you look at the Security View of a folder or of a non-folder object. Folder objects such as a folder or a Z Discussion can contain other objects.
Figure 3.7 Result of a submitted SQL query.
Figure 3.8 Security View of the database connection.
The Undo View (see Figure 3.9) is another view that is common with most Zope objects. Here, you can undo actions made in the current folder or one of its subfolders. Select the actions you want to undo and then click the Undo button below the list of actions.
Figure 3.9 Undo View of the database connection.
The Ownership View is also a common view in Zope (see Figure 3.10). It states either who created the current object or who took over the ownership of the object. When you create a new object in Zope, Zope registers you as the owner of this object.
However, any Zope user who has the role Owner, or whose role has the permission Take Ownership, can take over ownership of any object in Zope. Taking over ownership is done via the Ownership View. If you are allowed to take ownership, the Ownership View will look like Figure 3.11.
Figure 3.10 The Ownership View where the object is owned by the manager.
Figure 3.11 The Ownership View with the Take Ownership button.
Having ownership of an object can be important when executing methods in Zope.
In the Browse View, you can seeand browse throughthe content of the tables and rows that exist in the database that the Z Gadfly Database Connection is currently connected to (the data source of the connection). The view shows the name of the tables and the rows in the tables. It also shows the type of the rows. Figure 3.12 shows the Testtable table that contains three rows: Name, First_name, and Age. The types are shown by the images in front of the row names and the type names after the row names.
Figure 3.12 Browse View of the database connection.
At the time of writing, the Z Gadfly Database only supports the VARCHAR, INTEGER, and FLOAT field types. This is another reason why the Z Gadfly Database is only suitable for test purposes.
How to Create Different Z Gadfly Databases
When you created the Z Gadfly Database Connection earlier in the chapter, you selected the Demo database to be used with this connection. As mentioned before, you can use more than one database with a connection, but only one database at a time.
To create a new database that you can use with any Z Gadfly Database Connection, go to the /var/gadfly folder in your Zope installation folder. There you will find a subfolder /demo, which is where anything you have done so far with the demo database is being stored. Now, you just need to create a new folder in the /gadfly folder, and you can start creating tables in the new database.
You can either create a new Z Gadfly Database Connection for the new database and select the name of the new folder instead of Demo, or you can use the existing Z Gadfly Database Connection and change the data source in the Properties View.