Hi, 2017-04-05 9:44 GMT+02:00 Günce Kaya <guncekay...@gmail.com>:
> Hi all, > > I have some questions about calculating table and index size. > > I have a dummy table which has an integer column and its index. The table > has 1400000 rows and all of rows are same thats value is 20000000. Table > size is 50MB and index size is 31MB. Why there is too much size difference > between table and its index? what happen on data files when we add index? > > You have metadata informations in the table datafiles that you don't have on the index datafiles. For example, all the system columns for each line. > Second question is that after created table, table size was 0 byte. I > inserted a row as 120 then table size was 8192 byte. I inserted five times > same value to the table and table size is still 8192 bytes. Table size > changed after inserted lots of rows. Table size was stabile till first few > hundred rows. why table size didn't change when I inserted lots of rows? > > PostgreSQL works with 8KB blocks. When you insert a line, it puts it on a block, but this block may contain many lines. So your next new lines still fit in the first block... until it doesn't, and you'll see a new block coming, making your table datafile grows to 16KB. And so on and so on. -- Guillaume. http://blog.guillaume.lelarge.info http://www.dalibo.com
