Useful PostgreSQL Queries and Commands

postgres_queries_and_commands.sql

-- show running queries (9.2)
SELECT pid, client_addr, age(clock_timestamp(), query_start), usename, query, state 
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);

-- Show running trasactions
-- Long running transactions
SELECT
    pid,
    datname,
    usename,
    state,
    age(backend_xmin),
    query
FROM pg_stat_activity
WHERE
    backend_xmin IS NOT NULL
ORDER BY
    age(backend_xmin) DESC;

-- 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;

-- 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
                                                                                               
# Check if server is receiving connections
while true; do
  date;
  pg_isready -d tabletop -h kbs-pg-tabletop-prod.c779y6m0egib.us-west-2.rds.amazonaws.com -p 5432 -U tabletop_server_prod;
  sleep 5;
done