[PostgreSQL 10] compact pg_wal (former pg_xlog)

# du -xhd1 /var/lib/postgresql/10/main | grep -F M
36M     /var/lib/postgresql/10/main/base
769M    /var/lib/postgresql/10/main/pg_wal
804M    /var/lib/postgresql/10/main

# service postgresql stop
[ ok ] Stopping PostgreSQL 10 database server: main.

# /usr/lib/postgresql/10/bin/pg_controldata /var/lib/postgresql/10/main 2>&1 | grep Next
Latest checkpoint's NextXID:          0:2181
Latest checkpoint's NextOID:          19544
Latest checkpoint's NextMultiXactId:  1
Latest checkpoint's NextMultiOffset:  0

# sudo -u postgres /usr/lib/postgresql/10/bin/pg_resetwal -o 19544 -x 2181 -f /var/lib/postgresql/10/main/
Write-ahead log reset

# du -xhd1 /var/lib/postgresql/10/main | grep -F M
36M     /var/lib/postgresql/10/main/base
17M     /var/lib/postgresql/10/main/pg_wal
52M     /var/lib/postgresql/10/main

# service postgresql start
[ ok ] Starting PostgreSQL 10 database server: main.