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From: David Wall <d.wall@computer.org>
To: pgsql-performance@postgresql.org
Subject: DB size and TABLE sizes don't seem to add up
Date: Mon, 17 Feb 2014 14:14:44 -0800
Message-ID: <530289D4.20106@computer.org> (raw)
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I am running PG 9.2.4 and I am trying to figure out why my database size 
shows one value, but the sum of my total relation sizes is so much less.

Basically, I'm told my database is 188MB, but the sum of my total 
relation sizes adds up to just 8.7MB, which is 1/20th of the reported 
total.  Where is the 19/20th of my data then?  We do make significant 
use of large objects, so I suspect it's in there.  Is there a relation 
size query that would include the large object data associated with any 
OIDs in those tables?

Here's the data I am working off of:

First, I run a query to get my total DB size (this is after a restore 
from a backup, so it should not have too many "holes"):

bpn=# SELECT pg_size_pretty(pg_database_size('bpn'));
  pg_size_pretty
----------------
  188 MB
(1 row)

Second, I run this query (from 
http://wiki.postgresql.org/wiki/Disk_Usage) to get the total relation 
sizes for the tables in that database:

bpn=# SELECT nspname || '.' || relname AS "relation",
bpn-#     pg_size_pretty(pg_total_relation_size(C.oid)) AS "total_size"
bpn-#   FROM pg_class C
bpn-#   LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
bpn-#   WHERE nspname NOT IN ('pg_catalog', 'information_schema')
bpn-#     AND C.relkind <> 'i'
bpn-#     AND nspname !~ '^pg_toast'
bpn-#   ORDER BY pg_total_relation_size(C.oid) DESC;
                         relation                         | total_size
---------------------------------------------------------+------------
  public.esf_outbound_email_message                       | 1624 kB
  public.esf_transaction_activity_log                     | 968 kB
  public.esf_blob                                         | 560 kB
  public.esf_outbound_email_message_attachment            | 552 kB
  public.esf_tran_report_field_string                     | 232 kB
  public.esf_system_activity_log                          | 192 kB
  public.esf_permission_option_group                      | 184 kB
  public.esf_library_document_version_page                | 176 kB
  public.esf_transaction                                  | 152 kB
  public.esf_transaction_party                            | 136 kB
  public.esf_library_dropdown_version_option              | 128 kB
  public.esf_signature_key                                | 112 kB
  public.esf_transaction_document                         | 104 kB
  public.esf_permission_option                            | 96 kB
  public.esf_library_email_template_version               | 96 kB
  public.esf_transaction_party_document                   | 96 kB
  public.esf_field_template                               | 88 kB
  public.esf_transaction_party_assignment                 | 88 kB
  public.esf_outbound_email_message_response              | 88 kB
  public.esf_user_activity_log                            | 88 kB
  public.esf_library_buttonmessage                        | 80 kB
  public.esf_library_email_template                       | 80 kB
  public.esf_library_documentstyle                        | 80 kB
  public.esf_package                                      | 80 kB
  public.esf_package_version_party_template               | 80 kB
  public.esf_permission                                   | 80 kB
  public.esf_report_template                              | 80 kB
  public.esf_transaction_template                         | 80 kB
  public.esf_user                                         | 80 kB
  public.esf_userlogin                                    | 80 kB
  public.esf_group                                        | 80 kB
  public.esf_library                                      | 80 kB
  public.esf_library_document                             | 80 kB
  public.esf_library_dropdown                             | 80 kB
  public.esf_stats                                        | 80 kB
  public.esf_library_image                                | 80 kB
  public.esf_library_propertyset                          | 80 kB
  public.esf_package_version                              | 72 kB
  public.esf_package_version_document                     | 72 kB
  public.esf_report_template_report_field                 | 72 kB
  public.esf_library_document_version                     | 72 kB
  public.esf_library_documentstyle_version                | 72 kB
  public.esf_group_user                                   | 72 kB
  public.esf_report_field_template                        | 72 kB
  public.esf_library_buttonmessage_version                | 72 kB
  public.esf_library_propertyset_version                  | 72 kB
  public.esf_library_dropdown_version                     | 72 kB
  public.esf_party_template_field_template                | 72 kB
  public.esf_library_image_version                        | 72 kB
  public.esf_party_template                               | 72 kB
  public.esf_label_template                               | 56 kB
  public.esf_library_document_version_page_field_template | 56 kB
  public.esf_package_version_report_field                 | 56 kB
  public.esf_package_version_party_document_party         | 56 kB
  public.esf_session_key                                  | 56 kB
  public.esf_userlogin_history                            | 56 kB
  public.esf_deployment                                   | 56 kB
  public.esf_report_template_transaction_template         | 56 kB
  public.esf_library_serial                               | 24 kB
  public.esf_http_send_request                            | 24 kB
  public.esf_library_file                                 | 24 kB
  public.esf_tran_report_field_tranfileid                 | 16 kB
  public.esf_library_file_version                         | 16 kB
  public.esf_tran_report_field_long                       | 16 kB
  public.esf_http_send_response                           | 16 kB
  public.esf_tran_report_field_date                       | 16 kB
  public.esf_tran_report_field_numeric                    | 16 kB
  public.esf_library_serial_version                       | 16 kB
  public.esf_transaction_file                             | 16 kB
  public.esf_transaction_party_renotify                   | 16 kB
  public.esf_library_image_version_overlay_field          | 8192 bytes
(71 rows)

But when I add up those 71 rows, it's only 8,728,192 bytes (roughly 8.7MB).

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