How to optimize search with create index in Postgres

I have a database with 300,000,000 records,
To insert new records, I want to check whether the record is already in the database or not,
I use the following query to confirm:

SELECT student_code  FROM public.student_tbl  WHERE class_type='high_school' AND class_register='true' AND (student_code='F40101197X0' OR student_code='F40101197X1' OR student_code='F40101197X2');  

It will take 2 minutes to complete, it takes quite a while.
Therefore, I want to save the time to check data is already in the database or not by using the following query:

CREATE INDEX student_tbl_class_register_index  ON public.student_tbl(class_register)  WHERE class_register IS TRUE;   

Is it okay with the CREATE INDEX statement above?
Or how can I do well in this case, please tell me!
Any hint will be great. Thanks!

https://stackoverflow.com/questions/66467913/how-to-optimize-search-with-create-index-in-postgres March 04, 2021 at 10:54AM