Biggest databases

Human-readable size of every database, largest first

SELECT datname, pg_size_pretty(pg_database_size(datname)) AS size FROM pg_database ORDER BY pg_database_size(datname) DESC;

More postgres commands

Table and index sizes

SELECT relname, pg_size_pretty(pg_total_relation_size(oid)) AS total, pg_size_pretty(pg_relation_size(oid)) AS table FROM pg_class WHERE relkind='r' ORDER BY pg_total_relation_size(oid) DESC LIMIT 20;

Top tables by total size including indexes and TOAST
Find unused indexes

SELECT relname, indexrelname, idx_scan, pg_size_pretty(pg_relation_size(indexrelid)) AS size FROM pg_stat_user_indexes WHERE idx_scan=0 ORDER BY pg_relation_size(indexrelid) DESC;

Indexes never scanned (idx_scan=0); candidates to drop and reclaim space
Check autovacuum status

SELECT relname, n_dead_tup, last_autovacuum, last_autoanalyze FROM pg_stat_user_tables ORDER BY n_dead_tup DESC LIMIT 20;

Find tables with dead tuples and stale autovacuum runs
Reindex without locking

REINDEX INDEX CONCURRENTLY <name>; -- note: cannot run inside a transaction block

Rebuild a bloated index online; note: must run outside a transaction
Create index online

CREATE INDEX CONCURRENTLY idx_<name> ON <table>(col); -- monitor: SELECT * FROM pg_stat_progress_create_index;

Build index without blocking writes; track progress via pg_stat_progress_create_index