Editing an Existing Stored Program

There are two approaches to editing the text of existing stored programs. The easiest though probably not the bestway to edit an existing stored program is to use the MySQL Query Browser to edit the stored program in place. By "in place," we mean that you work directly with the copy of the stored program held in the database. A better way is to edit an external text file that contains the stored procedure code. We describe these approaches in the following subsections.

7.2.1. Editing a Program in Place

Editing a stored program in place is certainly easy, as shown in Figure 7-8. To edit an existing stored program in this way, you simply locate and select the stored program in the MySQL Query Browser's Schemata browser, right-click, and select Edit Procedure (or Edit Function) from the context menu. The relevant stored program code is loaded from the database into the edit window where you can make your changes. Clicking the Execute button runs the modified script and replaces the stored program in the database.

Figure 7-8. Editing a stored program in place with the MySQL Query Browser

7.2.2. Maintaining Stored Programs in External Files

There are a number of reasons why you may not want to edit stored programs in place, as we did in Figure 7-8:

• When you retrieve the text for a stored program from the database (as Query Browser and other similar programs do), you may find that the text of the stored program is slightly different from the version you originally created. In particular, the name of the stored routine may be quoted and the name of the database prepended. This prepending of the database name is a bad idea if you want to migrate stored programs to other databases.
• It is definitely best practice to use a source control system (such as Microsoft SourceSafe, Subversion, or CVS) to store each changed iteration of your stored program. This allows you to roll back changes to a stored program that turn out to be problematic, and allows you to retrieve a specific version of a program when multiple versions are in use.

Some third-party MySQL development tools allow you to load and save your stored program source directly into a version control system such as CVS. For instance, in Toad for MySQL we can check files in and out of CVS or SourceSafe from within our programming environment, as shown in Figure 7-9.

Figure 7-9. Toad for MySQL provides integration with version control systems

Regardless of whether your IDE directly supports integration with a version control system, you should still use version control to maintain stored program code. Rather than extract the stored program code from the database, you will extract it from an external file before editing, and you will save the external fileand check it into your version control systemwhen it is complete.

Figure 7-10 shows how we can perform these actions on a Linux system using the MySQL Query Browser as our editing environment and RCS as our version control system.

Figure 7-10. Maintaining stored program source code in a source control system

Let's work through the steps highlighted in Figure 7-10:

1. Before we get started, we need to extract the source file from the version control system and lock it for editing. In the RCS system this is done with the co -l command.
2. Now we can load the source file into an edit window in the MySQL Query Browser.
3. After making our edits, we can save our changes to the database by clicking the Execute button.
4. We can perform basic testing of the stored program by running it from within the Query Browser. Double-clicking the stored program name in the Schemata browser is one way to do this.
5. If we are satisfied that our changes are good, we can save them back to the disk file we originally loaded.
6. Now we check the changes back into version control. In RCS this is done with the ci command.