Recital

Login Register

In this article Barry Mavin, CEO and Chief Software Architect for Recital, details how to work with Triggers in the Recital Database Server.

Overview

A trigger is a special kind of stored procedure that runs when you modify data in a specified table using one or more of the data modification operations: UPDATE, INSERT, or DELETE.

Triggers can query other tables and can include complex SQL statements. They are primarily useful for enforcing complex business rules or requirements. For example, you can control whether to allow a new order to be inserted based on a customer's current account status.

Triggers are also useful for enforcing referential and data integrity.

Triggers can be used with any data source that is handled natively by the Recital Database Engine. This includes Recital, FoxPro, FoxBASE, Clipper, dBase, CISAM, and RMS data,

Creating and Editing Triggers

To create a new Trigger,  right-click the Procedures node in the Databases tree of the Project Explorer and choose Create. To modify an existing Trigger select the Trigger in the Databases Tree in the Project Explorer by double-clicking on it, or select Modify from the context menu. By convertion we recommend that you name your Stored Procedures beginning with "sp_xxx_", user-defined functions with "f_xxx_", and Triggers with "dt_xxx_", where xxx is the name of the table that they are associated with.

Associating Triggers with a Table

Once you have written your Triggers as detailed above you can associate them with the operations performed on a Table by selecting the Table tab.

The Tables tab allows you to select a Trigger procedure by clicking on the small button at the right of the Text field.

Types of Triggers

As can be seen from the Tables tab detailed below, The Recital Database Server handles 6 distinct types of Triggers.

Open Trigger

The Open Trigger is called after is a table is opened but before any operations are performed on it. You can use this trigger to record a log of table usage or provide a programmable means of checing security. If the Trigger procedure returns .F. (false), then the table is not opened. You can use a TRY...CATCH block around the associated command to inform the user.

Close Trigger

The Close Trigger is called just prior to a table being closed. In this trigger you may find it useful to get transaction counts by using the IOSTATS() built-in 4GL function, and record these values in a transaction log.

Update Trigger

The Update Trigger is called prior to a record update operation being performed. You can use this trigger to perform complex application or data specific validation. If the Trigger procedure returns .F. (false), then the record is not updated. You can use inform the user from within the Trigger procedure the reason that the data cannot be updated.

Delete Trigger

The Delete Trigger is called prior to a record delete operation being performed. You can use this trigger to perform complex application or data specific validation such as cross-table lookups e.g. attempting to delete a customer recortd when there are still open orders for that specific customer. If the Trigger procedure returns .F. (false), then the record is not deleted.

Insert Trigger

The Insert Trigger is called prior to a record insert (append) operation being performed. You can use this trigger to perform such tasks as setting up default values of columns within the record. If the Trigger procedure returns .F. (false), then the record is not inserted.

Rollback Trigger

The RollbackTrigger is called prior to a rollback operation being performed from within a form. If the Trigger procedure returns .F. (false), then the record is not rolled back to its original state.

Testing the Trigger

To test run the Trigger, select the Trigger in the Databases Tree in the Project Explorer by double-clicking on it. Once the Database Administrator is displayed, click the Run button to run the Trigger.

Published in Blogs
Read more...
When debugging C code it is common to write debugging to an external text file using the __FILE__ and __LINE__ preprocessor defines to trace execution flow.

Unfortunately java does not support __FILE__ and __LINE__ but you can get the same functionality with this code which can be placed in one of your libraries.
	
public static void showTrace(String msg)
{
	if (msg.length() > 0) System.out.println(msg);
	System.out.println("Trace: " + 
				   "file " + new Throwable().getStackTrace()[1].getFileName() +
				   " class " + new Throwable().getStackTrace()[1].getClassName() +
				   " method " + new Throwable().getStackTrace()[1].getMethodName() +
				   " line " + new Throwable().getStackTrace()[1].getLineNumber());
}
Published in Blogs
Read more...

We are pleased to announce the immediate availability of Recital 10.0.1.

Included in this version are:

  • Improved SQL query optimizer
  • *New* apache plugin for building Recital web apps on x86_64 (mod_recital64.so)
  • Performance improvements in connections to Recital Server and Recital Web.
  • Recital ODBC driver performance improvements and bug fixes
  • Miscellaneous bug fixes 
The download is available from http://www.recitalsoftware.com in the downloads section of our website.

Existing Recital 10 users can download the patch file and apply it to an existing installation.

Enjoy!
Published in Blogs
Read more...


I am pleased to finally report that the Centos release of Redhats 5.3 has been built and is available for download from http://www.centos.org/

The highlights of this release can be found at the following URL: http://www.redhat.com

The main areas of interest in my opinion excluding critical secirty fixes are:

  • Updated hardwaresupport support for the new Intel Core i7 (Nehalem) chips
  • Beefed up virtualiseation support increasing CPU and Ram limits of Virtual machines.
  • Inclusion of the fully open sourced OpenJDK. This makes Red Hat Enterprise Linux 5.3 the first enterprise-ready solution with a fully open source Java stack when combined with JBoss Enterprise Application Platform.


For those who already have Centos 5.2 installed you can simply receive the update via Yum.

Before you do the following, check that  you do not have 3rd party repo's and the Centos-testing repo enabled.

You can display the currently enabled repo's using the following command.

$ yum repolist



Then as root at the prompt type:

$ yum update

 

Published in Blogs
Read more...

If when your attempt to create device meta-data fails this is drbd preventing you from corrupting a file system present on the target partition.

$ drbdadm create-md drbd0

v08 Magic number not found
md_offset 30005817344
al_offset 30005784576
bm_offset 30004867072

Found ext2 filesystem which uses 190804004 kB
current configuration leaves usable 29301628 kB

Device size would be truncated, which
would corrupt data and result in
'access beyond end of device' errors.
You need to either
* use external meta data (recommended)
* shrink that filesystem first
* zero out the device (destroy the filesystem)
Operation refused.

Command 'drbdmeta /dev/drbd0 v08 /dev/sda4 internal create-md' terminated with exit code 40
drbdadm aborting

Once you have confirmed that the file system present on the target partition is no longer required at the prompt type the following:

Replace /dev/sdaX with the block device you are targeting.

dd if=/dev/zero of=/dev/sdaX bs=1M count=128

Once this has completed the drbdadm create-md drbd0 command will complete with a "success."

$ drbdadm create-md drbd0
v08 Magic number not found
v07 Magic number not found
v07 Magic number not found
v08 Magic number not found
Writing meta data...
initialising activity log
NOT initialized bitmap
New drbd meta data block successfully created.
success
$

 

Published in Blogs
Read more...
Recital's version of Samba allows application data to be shared and locked correctly across these systems, allowing a truly integrated heterogeneous data environment. For example Recital applications running on a UNIX/Linux server can read and update FoxPro databases residing on a Microsoft Windows NT server through the use of Samba.
You can view the modified changes by downloading the following files and patching these into your current Samba installation.
open.c (file opening and share modes)
version.h (versioning information)
The variable CPPFLAGS in the file Makefile will require the define -DRECITAL added to it.
In order to make the locking compatible between UNIX/Linux and Windows the following environment variable must be placed in the profile.db for Unix/Linux Developer and in profile.uas for the Universal Application Server:
DB_SAMBA=YES ;export DB_SAMBA 
The following settings need to be added to the smb.conf file to ensure that file names are always converted to lower case:
preserve case = no 
default case = lower 
mangle case = yes 
The following settings need to be added to the smb.conf file for locking to operate correctly:
oplocks = False
share modes = no
Published in Blogs
Read more...

Latest Development News

The Lianja Application Platform is a cost-effective cloud database computing platform for SMEs (Small and Medium-sized Enterprises) that lets them focus on developing and deploying business Apps without the need to invest in lengthy application development times and an expensive IT infrastructure.

The three pillars of Lianja are:
  • The Lianja App Builder
  • The Lianja Cloud Database
  • Lianja.com Apps
If you need to develop and deploy cross-platform Visual FoxPRO GUI, Web or Mobile Apps visit the Lianja website for further details.

Published in Blogs
Read more...
Each Recital table can have one or more data dictionaries to provide a central repository for constraints and other metadata. 

Here's how to set up field validation based on dynamic values from another table.

Using the products.dbf table from the southwind sample database, validation can be added to the categoryid field to ensure it matches an existing categoryid from the categories.dbf table.
open database southwind
alter table products add constraint;
(categoryid set check rlookup(products.categoryid,categories))
The rlookup() function checks whether an expression exists in the index (master or specified) of the specified table .  An attempt to update categoryid with a value not in the list will give an error: Validation on field 'CATEGORYID' failed.

If you have access to the Recital Workbench, you can use the modify structure worksurface to add and alter your dictionary entries, including a customized error message if required.

validation


Published in Blogs
Read more...
A really nice plugin for eclipse that lets you write/edit  Trac wiki pages in eclipse.

http://trac-hacks.org/wiki/EclipseTracPlugin
Published in Blogs
Read more...
Found a nice subversion plugin for finder on the MAC.

The goal of the SCPlugin project is to integrate Subversion into the Mac OS X Finder. 

  • Support for Subversion.
  • Access to commonly used source control operations via contextual menu [screenshot]
  • Dynamic icon badging for files under version control. Shows the status of your files visually. [ screenshot ]
Published in Blogs
Read more...
Twitter

Copyright © 2022 Recital Software Inc.

Login

Register

User Registration
or Cancel