Fast way to discover the row count of a table in P

Question

I need to know the number of rows in a table to calculate a percentage. If the total count is greater than some predefined constant, I will use the constant value. Otherwise, I will use the actual number of rows.

I can use SELECT count(*) FROM table. But if my constant value is 500,000 and I have 5,000,000,000 rows in my table, counting all rows will waste a lot of time.

Is it possible to stop counting as soon as my constant value is surpassed?

I need the exact number of rows only as long as it's below the given limit. Otherwise, if the count is above the limit, I use the limit value instead and want the answer as fast as possible.

Something like this:

SELECT text,count(*), percentual_calculus()  
FROM token  
GROUP BY text  
ORDER BY count DESC;

Answer 1

You can get the count by the below query (without * or any column names).

select from table_name;