In this article Barry Mavin, CEO and Chief Software Architect for Recital, gives details on Working with user-defined Functions in the Recital Database Server.
Overview
User-defined functions (UDFs) are collections of statements written in the Recital 4GL (compatible with Visual FoxPro) stored under a name and saved in a Database. User-defined functions are just-in-time compiled by the Recital database engine. User-defined functions can be used in SQL statements to extend the power and flexibility of the inbuilt functions. Using the Database Administrator in Recital Enterprise Studio, you can easily create, view, modify, and test Stored Procedures, Triggers, and user-defined functions.
Tip
You can also extend the Recital Database Server with C Extension Libraries and use the functions defined within that library also.Creating and Editing user-defined functions
To create a new User-defined function, right-click the Procedures node in the Databases tree of the Project Explorer and choose Create. To modify an existing User-defined function select the User-defined function in the Databases Tree in the Project Explorer by double-clicking on it or selecting Modify from the context menu. By convertion we recommend that you name your User-defined functions beginning with "f_xxx_", where xxx is the name of the table that they are associated with.
Testing the user-defined function
To test run the user-defined function, select it 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 it.
Example
Example: user-defined function "f_order_details_total".
////////////////////////////////////////////////////////////////////////
// example user-defined function
function f_order_details_total(pUnitprice, pQuantity, pDiscount)
return (pUnitprice + pQuantity + pDiscount) > 0
endfunc
Example: using the user-defined function in a SQL SELECT statement.
//////////////////////////////////////////////////////////////////////// // sample code to use a user-defined function in a SQL SELECT statement select * from customers where f_order_details_total(Unitprice, Quantity, Discount)
Using user-defined function libraries with the Recital Database Server
You can place all of the user-defined functions associated with a particular table into a procedure library. You then define an Open Trigger for the table that opens up the procedure library whenever the table is accessed. This is a much faster way of using user-defined functions as it reduces the amount of file open/close operations during a query and also simplifies development and maintenance.
By convertion we recommend that you should name the library using the convention "lib_xxx", where xxx is the name of the table that the library is associated with.
Example: procedure library in lib_order_details.
////////////////////////////////////////////////////////////////////////
// example user-defined functions
function f_order_details_total(pUnitprice, pQuantity, pDiscount)
return (pUnitprice * pQuantity - pDiscount) > 0
endfunc
function f_order_details_diff(pUnitprice, pQuantity, pDiscount, pValue)
return f_order_details_total(pUnitprice, pQuantity, pDiscount) - pValue
endfunc
Example: Open Trigger in dt_order_details_open.
//////////////////////////////////////////////////////////////////////// // This trigger will open up the procedure library when the table is opened set procedure to lib_order_details additive
Example: Close Trigger in dt_order_details_close.
//////////////////////////////////////////////////////////////////////// // This trigger will close the procedure library when the table is closed close procedure lib_order_details
Example: using the user-defined function in a SQL SELECT statement.
//////////////////////////////////////////////////////////////////////// // sample code to use a user-defined function in a SQL SELECT statement select * from customers where f_order_details_total(Unitprice, Quantity, Discount)
User-defined functions can also be used with any of the Client Drivers that work with the Recital Database Server.
$hdiutil create /tmp/tmp.dmg -ov -volname "RecitalInstall" -fs HFS+ -srcfolder "/tmp/macosxdist/"
$hdiutil convert /tmp/tmp.dmg -format UDZO -o RecitalInstall.dmg
Opening SSH to the outside world is a security risk. Here is how to restrict SSH access to certain IP addresses on a machine.
- Edit the /etc/hosts.allow file to include these lines, assuming your machine is on the 192.168.2.x nonrouting IP block, and you want to enable an external address of 217.40.111.121 IP block: Remember to add the period on the end of each incomplete IP number. If you have another complete IP address or range, add a space and that range on the end.
sshd,sshdfwd-X11: 192.168.2. 217.40.111.121
- Edit your /etc/hosts.deny file to include this line:
sshd,sshdfwd-X11:ALL
- These lines refuse SSH connections from anyone not in the IP address blocks listed.
Additionally you can restrict SSH access by username.
- Edit the /etc/ssh/sshd_config file and add the following lines
PermitRootLogin no
AllowUsers user1 user2 user3 etc
PasswordAuthentication yes
Now restart the ssh daemon for these changes to take effect
service sshd restart
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());
}
SET DATADIR TO [ <directory> ]This command is used to specify a directory where database tables, memos, indexes, and dictionary files are located. When a table is being opened this directory is searched first before the current directory and the file search path to locate the table and its associated files. This allows the database tables to be relocated to a different file system without the need to change an existing application.
try
open database southwind
catch
die("Cannot open database, please try later.")
endtry
http://kbala.com/ie-9-supports-corner-radius/
In this article Barry Mavin explains step by step how to setup a Linux HA (High Availability) cluster for the running of Recital applications on Redhat/Centos 5.3 although the general configuration should work for other linux versions with a few minor changes.
DB_SAMBA=YES ;export DB_SAMBA
preserve case = nodefault case = lowermangle case = yes
oplocks = False
share modes = no