PostgreSQL: How to show table sizes

When you have a large PG database, you may want to find out which tables are consuming the most disk space.
You can easily check this using the following SQL statement from the PostgreSQL wiki.

SELECT nspname || '.' || relname AS "relation",
    pg_size_pretty(pg_total_relation_size(C.oid)) AS "total_size"
  FROM pg_class C
  LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
  WHERE nspname NOT IN ('pg_catalog', 'information_schema')
    AND C.relkind <> 'i'
    AND nspname !~ '^pg_toast'
  ORDER BY pg_total_relation_size(C.oid) DESC
  LIMIT 5;

Example output:

       relation       | total_size 
----------------------+------------
 public.snapshots     | 823 MB
 public.invoice_items | 344 MB
 public.messages      | 267 MB
 public.topics        | 40 MB
 public.invoices      | 35 MB
(5 rows)

See the PostgreSQL wiki Data Usage Show archive.org snapshot page for more information on calculating sizes of databases or tables.

Connect to a Rails database with bin/rails dbconsole -p.

wiki.postgresql.org

Arne Hartherz

makandra.com

Say thanks49

Last edit

2023-07-20

Dominik Schöler

License

Source code in this card is licensed under the MIT License.

PostgreSQL: How to show database size

SELECT pg_size_pretty(pg_database_size('some-database'));

Example

SELECT pg_size_pretty(pg_database_size('cards_p'));
----------------
 13 GB
(1 row)

SELECT pg_database_size('cards_p');
 pg_database_size 
-------------...

MySQL: How to dump single tables instead of a complete database

Sometimes you want to test migrations with production or staging data. Dumping single tables makes sense if a complete dump would be to big.

mysqldump -u deploy_user -p application_production table1 table2 table2 > table1_table2_table2.sql.du...

PostgreSQL vs. Rails migration: How to change columns from string to integer

When writing Rails migrations to convert a string column to an integer you'd usually say:

change_column :table_name, :column_name, :integer

However, PostgreSQL will complain:

PG::DatatypeMismatch: ERROR:  column "column_name" cannot...

PostgreSQL: How to change attributes of a timestamp

It's generally not trivial to change a datetime's seconds, minutes, etc in SQL. Here is how it works when speaking PostgreSQL.

Consider you have a timestamp column whose seconds you want to zero:

SELECT born_at FROM users;
       born_at...

Posted by Arne Hartherz to makandra dev (2018-04-13 09:35)

PostgreSQL: How to show table sizes

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Option 1: Drop the entire schema

Example

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