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Useful PostgreSQL Queries and Commands
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-- show running queries (pre 9.2) | |
SELECT procpid, age(clock_timestamp(), query_start), 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(clock_timestamp(), query_start), usename, query | |
FROM pg_stat_activity | |
WHERE query != '<IDLE>' AND query NOT ILIKE '%pg_stat_activity%' | |
ORDER BY query_start desc; | |
-- kill running query | |
SELECT pg_cancel_backend(procpid); | |
-- kill idle query | |
SELECT pg_terminate_backend(procpid); | |
-- vacuum command | |
VACUUM (VERBOSE, ANALYZE); | |
-- 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; | |
SELECT | |
t.schemaname, | |
t.tablename, | |
c.reltuples::bigint AS num_rows, | |
pg_size_pretty(pg_relation_size(c.oid)) AS table_size, | |
psai.indexrelname AS index_name, | |
pg_size_pretty(pg_relation_size(i.indexrelid)) AS index_size, | |
CASE WHEN i.indisunique THEN 'Y' ELSE 'N' END AS "unique", | |
psai.idx_scan AS number_of_scans, | |
psai.idx_tup_read AS tuples_read, | |
psai.idx_tup_fetch AS tuples_fetched | |
FROM | |
pg_tables t | |
LEFT JOIN pg_class c ON t.tablename = c.relname | |
LEFT JOIN pg_index i ON c.oid = i.indrelid | |
LEFT JOIN pg_stat_all_indexes psai ON i.indexrelid = psai.indexrelid | |
WHERE | |
t.schemaname NOT IN ('pg_catalog', 'information_schema') | |
ORDER BY 1, 2; | |
-- 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; | |
-- 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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