Coalesce to reduce partitions before writing to hive is not working

final_store.coalesce(5).write.mode("overwrite").insertInto("database.tablename",overwrite = True), this statement is not merging partitions. I've set 

.config("spark.default.parallelism", "2000") \
.config("spark.sql.shuffle.partitions", "2000") \

however repartition is working but takes 20-25 minutes to insert.