kettle processRow

public boolean processRow(StepMetaInterface smi, StepDataInterface sdi) throws KettleException { 

    meta = (LookupStepMeta) smi;
    data = (LookupStepData) sdi; 

    Object[] r = getRow(); // get row, blocks when needed!
    if (r == null) // no more input to be expected...
    {
        setOutputDone();
        return false;
    } 

    if (first) { 

        first = false; 

        // the size of the incoming rows
        data.inputSize = getInputRowMeta().size(); 

        // determine output field structure
        data.outputRowMeta = (RowMetaInterface) getInputRowMeta().clone();
        meta.getFields(data.outputRowMeta, getStepname(), null, null, this); 

        // stores default values in correct format
        data.defaultObjects = new Object[meta.getKeyField().length]; 

        // stores the indices where to look for the key fields in the input rows
        data.keyFieldIndex = new int[meta.getKeyField().length];
        data.conversionMeta = new ValueMetaInterface[meta.getKeyField().length]; 

        for (int i=0;i<meta.getKeyField().length;i++){ 

            // get output and from-string conversion format for each field
            ValueMetaInterface returnMeta = data.outputRowMeta.getValueMeta(i+data.inputSize); 

            ValueMetaInterface conversionMeta = returnMeta.clone();
            conversionMeta.setType(ValueMetaInterface.TYPE_STRING);
            data.conversionMeta[i] = conversionMeta; 

            // calculate default values
            if (!Const.isEmpty(meta.getOutputDefault()[i])){
                data.defaultObjects[i] = returnMeta.convertData(data.conversionMeta[i], meta.getOutputDefault()[i]);
            }
            else{
                data.defaultObjects[i] = null;
            } 

            // calc key field indices
            data.keyFieldIndex[i] = data.outputRowMeta.indexOfValue(meta.getKeyField()[i]);
            if (data.keyFieldIndex[i]<0)
            {
                throw new KettleStepException(BaseMessages.getString(PKG, "VoldemortStep.Error.UnableFindField",meta.getKeyField()[i],""+(i+1)));
            } 

        } 

    } 

    // generate output row, make it correct size
    Object[] outputRow = RowDataUtil.resizeArray(r, data.outputRowMeta.size()); 

    // fill the output fields with look up data
    for (int i = 0, outi=data.inputSize;i<meta.getKeyField().length;outi++, i++){ 

        // try to get the value from voldemort
        String value = data.voldemortClient.getValue(r[data.keyFieldIndex[i]]); 

        // if nothing is there, return the default
        if (value == null){
            outputRow[outi] = data.defaultObjects[i];
        }
        // else convert the value to desired format
        else{
            outputRow[outi] = data.outputRowMeta.getValueMeta(outi).convertData(data.conversionMeta[i], value);
        } 

    } 

    // copy row to possible alternate rowset(s)
    putRow(data.outputRowMeta, outputRow);  

    // Some basic logging
    if (checkFeedback(getLinesRead())) {
        if (log.isBasic()) logBasic("Linenr " + getLinesRead());
    } 

    return true;
}

http://type-exit.org/adventures-with-open-source-bi/2010/06/developing-a-custom-kettle-plugin-looking-up-values-in-voldemort/

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