Thread: PostgreSQL 9.5.14 Documentation /Chapter 28 / 28.1. Determining DiskUsage

PostgreSQL 9.5.14 Documentation /Chapter 28 / 28.1. Determining DiskUsage

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Page: https://www.postgresql.org/docs/9.5/static/disk-usage.html
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PostgreSQL 9.5.14 Documentation / Chapter 28. Monitoring Disk Usage / 28.1.
Determining Disk Usage
(Applies for other Versions, too.)

I'm wondering if the two statements given showing the index space size as
described. 
I've the impression they show the space size of the tables.  

Regards --Michael


Extract of the manual:

You can easily display index sizes, too:
SELECT c2.relname, c2.relpages
FROM pg_class c, pg_class c2, pg_index i
WHERE c.relname = 'customer' AND
      c.oid = i.indrelid AND
      c2.oid = i.indexrelid
ORDER BY c2.relname;

       relname        | relpages
----------------------+----------
 customer_id_indexdex |       26


It is easy to find your largest tables and indexes using this information:
SELECT relname, relpages
FROM pg_class
ORDER BY relpages DESC;

       relname        | relpages
----------------------+----------
 bigtable             |     3290

Re: PostgreSQL 9.5.14 Documentation /Chapter 28 / 28.1. DeterminingDisk Usage

From
"David G. Johnston"
Date:
On Wed, Sep 5, 2018 at 4:43 AM, PG Doc comments form <noreply@postgresql.org> wrote:
I'm wondering if the two statements given showing the index space size as
described.
I've the impression they show the space size of the tables.  

"Each page is typically 8 kilobytes. (Remember, relpages is only updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.)"

So while it takes a bit of interpretation it is stated that "relpages" are not a size on their own but a value to be multiplied by 8k to come up with the disk size (typically since one can compile the server with a different page size).

David J.