Show WAL size and current LSN

Command

SELECT pg_current_wal_lsn() AS current_lsn, pg_walfile_name(pg_current_wal_lsn()) AS current_wal_file, pg_size_pretty(sum(size)) AS wal_dir_size FROM pg_ls_waldir();

What it does

Returns the current WAL LSN, the name of the WAL file being written and the total size of the pg_wal directory.

When to use it

To monitor WAL accumulation, disk usage and checkpoint spacing.

Caution

pg_ls_waldir and pg_walfile_name are available in PostgreSQL 10+; access may require the pg_monitor role.