In Pentaho Data Integration (PDI), for a variable to be substituted in the metadata of a step (like the SQL query in a Table input step), it must be defined in a scope accessible when the transformation initializes. The standard and correct method is to set the variable in the parent job before the transformation entry is executed. Using a "Set Variables" job entry accomplishes this. The job sets the variable, and the subsequent transformation inherits it, allowing the $(tablename) reference to be correctly resolved when the Table input step is prepared for execution.

A. The Get Variables step is used within a transformation to read variable values into the data stream as fields, not to set variables for metadata substitution in other steps.

C. The ? character is a parameter marker for prepared statements. It is used to safely insert data values (e.g., in a WHERE clause), not for dynamic SQL identifiers like table or column names.

D. A Set Variables step inside a transformation runs as part of the data flow. The Table input step is initialized before any rows are processed, so it cannot use a variable set by another step in the same data flow.

1. Hitachi Vantara Documentation

Pentaho Data Integration Concepts

"Variables": This documentation explains variable scope and inheritance. It clarifies that variables set in a job are passed down to the transformations and jobs that it executes. This principle supports setting the variable at the job level (Option B) to make it available to the transformation.

Reference: See the section on "Variable Scopes and Types" in the official Pentaho Data Integration documentation. It details how variables set with "Valid in the parent job" or "Valid in the root job" scopes are inherited.

2. Hitachi Vantara Documentation

PDI Job Entry Reference

"Set Variables": The documentation for the "Set Variables" job entry explicitly states its purpose is to define variables that can be used by subsequent entries within the same job. This directly aligns with the correct pattern described in Option B.

Reference: Official Hitachi Vantara Pentaho documentation for the "Set Variables" job entry.

3. Hitachi Vantara Documentation

PDI Transformation Step Reference

"Table Input": The documentation for this step specifies that variable substitution (using ${...} or $(...)) occurs when the "Replace variables in script?" option is enabled. This substitution happens during the initialization phase of the step

before data flow begins

reinforcing why the variable must be set beforehand (as in Option B) and not during the flow (as in Option D).

Reference: Official Hitachi Vantara Pentaho documentation for the "Table Input" transformation step.