Re: calculating table and index size

Hello,

try pgstattuple() and pgstatindex() , I think you will figure it out.

Steven

2017-04-05 16:56 GMT+08:00 Guillaume Lelarge <guillaume(at)lelarge(dot)info>:

> Hi,
>
> 2017-04-05 9:44 GMT+02:00 Günce Kaya <guncekaya14(at)gmail(dot)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
>