sql - Is it possible to get the number of rows from a table in O(1) time? -


in sql server, 1 way of getting number of rows in table is

select count(*) mytable 

but assume that's o(n) time n number of rows. there metadata can access has number of rows stored?

yes, can use sys.partitions, might not exact number, it's extremely fast:

select sum(rows)  sys.partitions [object_id] = object_id('dbo.mytable') , index_id in (0,1); 

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