vacuum-full-cluster
errorVACUUM FULL / CLUSTER
Why it's unsafe
VACUUM FULL and CLUSTER rewrite the entire table under an ACCESS EXCLUSIVE lock — minutes to hours of blocked reads and writes, plus 2x disk.
Safe rewrite
Use pg_repack for online table/space maintenance; plain VACUUM (no FULL) takes only SHARE UPDATE EXCLUSIVE and allows concurrent reads and writes.
Example
Try it in the playground →Unsafe
VACUUM FULL users;