SQL snippets for PostgreSQL

Size of transaction log

select sum((pg_stat_file('pg_xlog/' || file)).size)
from pg_ls_dir('pg_xlog') as file
where file ~ '^[0-9A-F]';

Size of tables in current database

select relname,pg_relation_size(oid) as size
from pg_class
where relkind = 'r' and relname not like 'pg_%' order by size desc;