[ioltas]

An advantage of REINDEX CONCURRENTLY is that it becomes much easier to handle dependencies of a rebuilt index with constraints, as what the feature roughly does it to add a swapping phase between the creation and the drop portions which switches the dependencies from the old index to the new fresh one. Table-level reindex also makes life easier.

The feature is equivalent to external tools like pg_repack (formerly pg_reorg) in more performant, and has a couple of limitations to be aware of: https://www.postgresql.org/docs/12/sql-reindex.html#SQL-REIN...