nice :) maybe part of msql? :) very old times nice, i will stay updated with this gson project, very interesting and a very good work :) 2014-05-27 15:35 GMT-03:00 Sergei Golubchik <serg@mariadb.org>:
Hi, Roberto!
On May 27, Roberto Spadim wrote:
Hi Sergei! nice :) i'm reading about it just one doubt i didn't understand everything yet there's a read time and a scan time, what the difference? read = sequencial read and scan = non sequencial read? or something like table read cost, index read cost?
Yes, the handler methods are:
virtual double handler::scan_time() { return stats.data_file_length / IO_SIZE + 2; } virtual double handler::read_time(uint index, uint ranges, ha_rows rows) { return ranges+rows; }
these are the default implementations, in the base handler class. Method names are historical and *very* old.
The return values are kind of "number of disk seeks". You can see that scan_time() assumes a sequential disk read of blocks of IO_SIZE bytes.
While read_time() assumes random reads of 'rows' rows from the data file and 'ranges' ranges from the index.
These default implementations, I suspect, predate even MyISAM.
Regards, Sergei
-- Roberto Spadim SPAEmpresarial Eng. Automação e Controle