If you have enabled performance optimization by enabling statistics it will come from there if the underlying file format supports infile statistics (like ORC), it will come from there if its just plain vanilla text file format, it needs to run a job to get the count so the longest of all
On Tue, Mar 22, 2016 at 12:44 PM, Amey Barve <ameybarv...@gmail.com> wrote: > select count(*) from table; > > How does hive evaluate count(*) on a table? > > Does it return count by actually querying table, or directly return count > by consulting some statistics locally. > > For Hive's Text format it takes few seconds while Hive's Orc format takes > fraction of seconds. > > Regards, > Amey > -- Nitin Pawar
