How to restore backup file to postgres docker container

I created a new server for redash 5.0 using docker and want to restore my backup postgressql file to the new server
I tried using this command :
cat ~/backup_redash_postgres.sql | docker exec -i redash_postgres_1 psql -U postgres
but got a list of errors like duplicate key found, function already exists etc

I am not able to restore backup file to postgres container. How can i solve this problem?