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Useful PostgreSQL Queries and Commands
-- show running queries (pre 9.2)
SELECT procpid, age(query_start, clock_timestamp()), usename, current_query
FROM pg_stat_activity
WHERE current_query != '<IDLE>' AND current_query NOT ILIKE '%pg_stat_activity%'
ORDER BY query_start desc;
-- show running queries (9.2)
SELECT pid, age(query_start, clock_timestamp()), usename, query
FROM pg_stat_activity
WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%'
ORDER BY query_start desc;
-- show queries longer than 5 mins
now() - pg_stat_activity.query_start AS duration,
FROM pg_stat_activity
WHERE (now() - pg_stat_activity.query_start) > interval '5 minutes';
-- kill running query
SELECT pg_cancel_backend(procpid);
-- kill idle query
SELECT pg_terminate_backend(procpid);
-- vacuum command
-- all database users
select * from pg_stat_activity where current_query not like '<%';
-- all databases and their sizes
select * from pg_user;
-- all tables and their size, with/without indexes
select datname, pg_size_pretty(pg_database_size(datname))
from pg_database
order by pg_database_size(datname) desc;
-- cache hit rates (should not be less than 0.99)
SELECT sum(heap_blks_read) as heap_read, sum(heap_blks_hit) as heap_hit, (sum(heap_blks_hit) - sum(heap_blks_read)) / sum(heap_blks_hit) as ratio
FROM pg_statio_user_tables;
-- table index usage rates (should not be less than 0.99)
SELECT relname, 100 * idx_scan / (seq_scan + idx_scan) percent_of_times_index_used, n_live_tup rows_in_table
FROM pg_stat_user_tables
ORDER BY n_live_tup DESC;
-- how many indexes are in cache
SELECT sum(idx_blks_read) as idx_read, sum(idx_blks_hit) as idx_hit, (sum(idx_blks_hit) - sum(idx_blks_read)) / sum(idx_blks_hit) as ratio
FROM pg_statio_user_indexes;
-- table index size
select pg_size_pretty(pg_total_relation_size('test_table') - pg_relation_size('test_table'));
-- table size
select pg_size_pretty(pg_total_relation_size('test_table'));
-- table size without indexes
select pg_size_pretty(pg_relation_size('test_table'));
-- Dump database on remote host to file
$ pg_dump -U username -h hostname databasename > dump.sql
-- Import dump into existing database
$ psql -d newdb -f dump.sql
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