Scripting

Since JDK 6 and later comes with a JavaScript engine, Jaqy uses it to provide scripting support.

Each JaqyInterpreter has a JavaScript engine. Since Jaqy currently only uses a JaqyInterpreter, there is effectively just one script engine.

Commands

• .eval is used to execute a one-liner JavaScript
• .script is used to execute a block of JavaScript from a file.

Variables

The following variables are set up by default. These variables are all in the engine scope.

Variable	Description
activityCount	The number of rows in the SQL query or SQL update.
display	Display
esc	Escape
globals	Globals
iteration	The current repeat iteration.
interpreter	JaqyInterpreter
parent	Parent variables (i.e. variables in the global scope)
session	Current Session

Expression Expansion

By default, Jaqy does expression expansion for all SQL statements. The general syntax is ${ expression }. It should be noted that Jaqy does an extremely simple regular expression match by looking for the pair of tokens, and evaluate the text in between using JavaScript.

The expression expansion can be disabled by using .expansion command.

Note

The reason to use ${ and } pair instead of $( and ) pair as in bash arithmetic expansion is simply because it is possible to allow functions to be called without complex parsing.

Jaqy does use $( and ) pair when dealing with .alias command arguments. So comparing to bash’s parameter expansion, the usage of the tokens are somewhat switched.

Expression Expansion Example 1

CREATE TABLE MyTable (a INTEGER, b INTEGER);
CREATE TABLE ControlTable (a INTEGER, b INTEGER);

INSERT INTO MyTable VALUES (1, 1);
INSERT INTO MyTable VALUES (2, 2);

SELECT * FROM MyTable;

-- Variable Substitution
INSERT INTO ControlTable VALUES (1, ${activityCount});

SELECT * FROM ControlTable;

The result should be the following.

a b
- -
1 2

Expression Expansion Example 2

The expression expansion evaluation ignores quotes etc. Such behavior is intentional, since it allows custom string values to be generated.

CREATE TABLE geoTable (a INTEGER, geo VARCHAR(100));

.script
var rad = 1.1234;
var x = Math.sin (rad);
.end script

INSERT INTO geoTable VALUES (1, 'POINT(${x} ${Math.cos(rad)})');

SELECT * FROM geoTable;

The result should be the following.

a geo
- --------------------------------------------
1 POINT(0.901576557064293 0.43261959242745307)

JavaScript Tips

Calling Java Functions

It is possible to call Java functions in JavaScript by using Packages variable.

.script
Packages.java.lang.System.out.println ( 'test' )
.end script

Implementing Java Interface

It is entirely possible to write plugins for Jaqy purely using JavaScript. Of course, its performance is not going to be that great. However, if you needed something done quickly, it could be an option.

.script
{
        var myCommand = new Packages.com.teradata.jaqy.command.JaqyCommandAdapter (
        {
                getDescription : function ()
                {
                        return "my dummy command";
                },
                execute : function (args, silent, globals, interpreter)
                {
                        interpreter.println ("my dummy command called.");
                }
        });
        globals.getCommandManager ().addCommand ("mycmd", myCommand);
}
.end script
-- now test the new .mycmd command
.mycmd