DSQL map features

The @emit annotation is placed before an assignment statement in a SELECT block. It allows you to conditionally produce output fields based on the evaluation of a condition expression.

If the condition evaluates to true, the output field is produced. If the condition evaluates to false, the field is omitted from the output.

Syntax

@emit ( condition = <expression> )
<field_name> = <value>

Arguments

The @emit annotation requires one mandatory argument:

• condition: A boolean expression that determines whether the field is produced.

Example

In this example, the rating field is included in the output only when it has a value:

FROM customer
SELECT {
  name = name,
  @emit ( condition = hasValue(rating) )
  rating = rating
}

This produces output records with the name field always present, but the rating field only appears when the customer has a rating value.

You can use the getContextVariable function to call a context variable defined in your Talend Studio Job.

Arguments

Name of the context variable.

Examples

• Using context variables in a DSQL map

You can use the getMapProperty function to retrieve the value of an execution property. This function is particularly useful in Camel Routes (including the cMap component) to access exchange inbound headers.

Arguments

Name of the execution property as a string literal.

Examples

getMapProperty('propertyName')

If the specified property does not exist, the function returns null.

You can use the java:call feature to call a Java method. This can be used to call beans and routines available in Talend Studio for example.

Arguments

Java parameters.

Examples

• Using beans and routines in a DSQL map