i want to search different models and fetch values for entered string in every model…how can i do that…pls help

you cannot simply do that. you need to query every model separately or use some external index, like Solr and query that index.

…or simulate such index with additional table where you put model name, id and all texts mixed together, and you query this single table for results and then create model instances based on model nam and its id from that table.