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Recital 10 introduced the ECHO command. This command operates in the same way as the PHP ECHO command. It does not append a newline to the output but rather operates in the same way as the existing ?? command in Recital. The string being output can contain C-style string escapes \n \t or \r (newline, tab and carriage return respectively) e.g.
echo "Hello world\n"
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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.

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Recital is a dynamic programming language particularly suited to the development of database applications. While Recital still supports standard procedural programming, new extensions to the language give you the power and flexibility of object-oriented programming. Object-oriented design and object-oriented programming represent a change in focus from standard procedural programming. This short primer will give you a good understanding of how to program object-oriented Recital.
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When the node is clicked set editable to false. Set editable to true in the double-click event handler.
// the click event handler 
private function onclick_sourcetree(e:Event):void  {     
    yourTree.editable = false; 
}  

// the doubleclick event handler  
private function ondoubleclick_sourcetree(e:Event):void  {     
    yourTree.editable = true;    
    yourTree.editedItemPosition = {columnIndex:0, rowIndex:sourceTree.selectedIndex}; 
} 
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After split brain has been detected, one node will always have the resource in a StandAlone connection state. The other might either also be in the StandAlone state (if both nodes detected the split brain simultaneously), or in WFConnection (if the peer tore down the connection before the other node had a chance to detect split brain).

At this point, unless you configured DRBD to automatically recover from split brain, you must manually intervene by selecting one node whose modifications will be discarded (this node is referred to as the split brain victim). This intervention is made with the following commands:

# drbdadm secondary resource 
# drbdadm disconnect resource
# drbdadm -- --discard-my-data connect resource


On the other node (the split brain survivor), if its connection state is also StandAlone, you would enter:

# drbdadm connect resource


You may omit this step if the node is already in the WFConnection state; it will then reconnect automatically.

If all else fails and the machines are still in a split-brain condition then on the secondary (backup) machine issue:

drbdadm invalidate resource
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The ShellEd plugin is a good shell editor for Eclipse
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Recital is a dynamic programming language with an integrated high performance database particularly well suited for the development and deployment of high transaction throughput applications.  Recital 10 further enhances Recital with extensive features and functionality to facilitate its use in fault tolerant high availability systems. Much of the development of Recital 10 was concentrated on performance optimizations and cluster aware functionality to provide an application platform that can be scaled as needed without any application changes. 

Key features of Recital 10 include:

  • Cluster aware database engine that works transparently with drbd, heartbeat, glusterfs and samba
  • High degree of fault tolerance with self healing indexes
  • Massive performance improvements 
  • Extensive internals overall and modernization with superior object-oriented capabilities
  • Chronological data versioning with database timelines
  • SmartQuery caching
  • Database Administration Tools
  • Code and Data Profiling
  • Better integration with unix/linux command shell
  • Incorporates a range of new built-in functions compatible with those in the PHP core libraries
  • Built-in support for outputting data in HTML, XML, and JSON format
  • Seamless SQL command integration into the Recital scripting language
  • Much improved Microsoft FoxPRO language compatibility
  • Numerous extensions and improvements (see below for details)
  • Very large file support (2^63)
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Recital 10.0 introduced the COPY DATABASE <name> TO <name> command.. The full syntax is;
COPY DATABASE <name> TO <name>  [ IF [ NOT ] EXISTS ] 
This command is used to copy an existing database to a new database. By default an error will be returned if the target database already exists. Specifying the optional IF NOT EXISTS keywords no error will be returned if the target database already exists. If the optional IF EXISTS keywords are specified and the target database already exists, then it will be removed before the copy. Both the databases must be closed before they can be copied.
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Key features of the Recital database include:

  • SQL-92 and a broad subset of ANSI SQL 99, as well as extensions
  • Cross-platform support
  • Stored procedures
  • Triggers
  • Cursors
  • Updatable Views
  • System Tables
  • Query caching
  • High-performance
  • Single-User and Multi-User
  • Multi-Process
  • ACID Transactions
  • Referential Integrity
  • Cascading Updates and Deletes
  • Multi-table Joins
  • Row-level Locking
  • BLOBs (Binary Large Objects)
  • UDFs (User Defined Functions)
  • OLTP (On-Line Transaction Processing)
  • Drivers for ODBC, JDBC, and .NET
  • Sub-SELECTs (i.e. nested SELECTs)
  • Embedded database library
  • Database timelines providing data undo functionality
  • Fault tolerant clustering support
  • Hot backup
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