@Field
    public void setReportVariables(List<String> variables) {
        reportVariables = variables;
    }
ADVANCED: This is used to set the variables in the prepared statement for
the report. This needs to be coordinated with {@link #setReportSql(String)}.
The available variables are "id, status, timestamp". If you're modifying to an update
statement like "update table tika_status set status=?, timestamp=? where id = ?"
then the values for this would be ["status", "timestamp", "id"].
<p/>
The default for the insert is ["id", "status", "timestamp"]
@param variables
tika-pipes/tika-pipes-reporters/tika-pipes-reporter-jdbc/src/main/java/org/apache/tika/pipes/reporters/jdbc/JDBCPipesReporter.java