Re: table and index size

On Mon, 15 Jul 2002, Damon Fasching wrote:

> Is there a way to determine the size of a table? an index?

The pg_class table has the size of every object in (usually 8K) pages. So:

    SELECT relname, reltype, relpages, relpages / 128 AS MB
    FROM pg_class
    WHERE relname LIKE 'session%'

or whatever.

> I created a table with two int4 columns and inserted 100 K rows.  The
> change in disk usage was only 4.3 KBytes, or .17 bits per integer.

Something's wrong there. Did you sync? 430 KB I'd believe.

> 1) Do these numbers seem reasonable to someone with a little more
> Postgresql experience?

No, they're completely out to lunch. ints are 4 bytes. postgres
row overhead is around about 40 bytes or so.

> One further question, if anyone can comment.  I have the New Riders
> PostgreSQL Essential Reference book.  It claims that in my database
> directory I should find some files with plain text names.

It's based on an old version of postgres. Now we use the object
IDs. So change the above query:

    SELECT relname, reltype, relfilenode, relpages, relpages / 128 AS MB
    FROM pg_class
    WHERE relname LIKE 'session%'

cjs
--
Curt Sampson  <cjs@cynic.net>   +81 90 7737 2974   http://www.netbsd.org
    Don't you know, in this new Dark Age, we're all light.  --XTC