@Vigneshraja Palaniraj​  yes i agree with you photon is not useful here. As per your suggestion will try to see what can be done by enabling memory like cluster nodes for this part. As of now i am checking query tuning and observing any data elements can be reduced here in selection based on business approval. However, it is lengthy process and want to avoid it. In the job log only one task is running and that is why i am surprised. The no of nodes didnt even helped in this part of code