How can accumulate a column, only if the column really exists?

In my setup() I want to create following datastore:

 $this->src("warehouse_datasource")
        ->query("
                SELECT   dim.tDate.DateMonthNameDE, COUNT(fact.tJob.JobID) AS amount, dim.tDate.DateYear, dim.tDate.DateMonth
                FROM     fact.tJob INNER JOIN
                         dim.tDate ON fact.tJob.JobCreatedDateID = dim.tDate.DateID
                WHERE   (fact.tJob.JobCompanyID = :CompanySiteCompanyID
                     AND (:JobCompanySiteID     = -1 OR fact.tJob.JobCompanySiteID = :JobCompanySiteID)
                     AND (:JobOwnerAccountID    = -1 OR fact.tJob.JobOwnerAccountID = :JobOwnerAccountID)
                     AND (:JobTypeID            = 255 OR fact.tJob.JobTypeID = :JobTypeID)
                     AND (:JobPositionID        = 255 OR fact.tJob.JobPositionID = :JobPositionID)
                     AND (:JobEducationID       = 255 OR fact.tJob.JobEducationID = :JobEducationID)
                     AND ( dim.tDate.DateYear >= :YearMin AND dim.tDate.DateYear <= :YearMax)
                    )
                GROUP BY dim.tDate.DateYear, dim.tDate.DateMonthNameDE, dim.tDate.DateMonth
                ORDER BY dim.tDate.DateYear, dim.tDate.DateMonthNameDE
                            ")
        ->params(array(
            ":CompanySiteCompanyID"=>$this->params["CompanySiteCompanyID"],
            ":JobCompanySiteID" =>$this->params["JobCompanySiteID"],
            ":JobOwnerAccountID"=>$this->params["JobOwnerAccountID"],
            ":JobTypeID"        =>$this->params["JobTypeID"],
            ":JobPositionID"    =>$this->params["JobPositionID"],
            ":JobEducationID"   =>$this->params["JobEducationID"],
            ":YearMin"          =>$this->params["YearRange"][0],
            ":YearMax"          =>$this->params["YearRange"][1],
        ))

        ->pipe(new AccumulativeColumn(array(
            "running_amount"=>"amount"
        )))
        ->pipe($this->dataStore('time_jobs_created'));

In my query I have some conditions. Thats why there are sometimes no data available. Therefore, the column "amount" will not always be created for counting the row.

After the query i use AccumulativeColumn to accumulate the amount of the counted columns. But when there is no amount column the AccumulativeColumn.php throws a: 'Undefined array key "amount"' exception.

I already tried to use the ->pipeIf() method, but I don't know how I can check if a column exists or not. How could I do that?

I tried it. But it doesn't work. I still have the same exception.

It doesn't work because in the case of the exception. I don't have a single row.

What I really want is: If the dataset is empty after the query, I want stop processing.

After that I want to render a chart with a dummy row. For Example: "DateYear" = 2023, "amount" = 0 or just a text like "There are no data available for this parameter"

Do you know how I can check if there is not a single row before I call the AccumulativeColumn process?

This is my chart

LineChart::create(array(
                        "title"=>"Gesamt erstellte Jobs",
                        "dataSource"=>$this->dataStore('time_jobs_created'),
                        "columns"=>array(
                            "DateYear"=>array(
                                "label"=>"Monat"
                            ),
                            "running_amount"=>array(
                                "label"=>"Gesamt erstellte Jobs",
                                "type"=>"number",
                            )
                        ),
                        "options" => array(
                            "backgroundColor"=>"transparent",
                            "hAxis" => array(
                                "showTextEvery" => 12,
                            ),
                        )
                    ));

This worked for me:

// Jobs.php

$this->src("warehouse_datasource")
        ->query(...)
        ->params(...)
        ->pipe($this->dataStore("time_jobs_created"));

// Jobs.view.php

use \koolreport\processes\AccumulativeColumn;
...

if ($this->dataStore('time_jobs_created')->count() !== 0) {
                        LineChart::create(array(
                            ...
                            "dataSource"=>$this->dataStore('time_jobs_created')->process(new AccumulativeColumn(array(
                                "running_amount"=>"amount"
                            ))),
                            ...
                        ));
                    } else {
                        echo "There is no data available for this condition.";
                    }

I was not able to prepare the whole dataStore in the setup(). Because after I have the boolean $emptyData, I'm not able to reprocess a saved dataStore and saving it as another dataStore.

But thank you for your help :)