Обсуждение: CREATE INDEX ONLY on a partitioned table?

Postgresql 12.5.

https://www.postgresql.org/docs/12/ddl-partitioning.html mentions creating 
indices on children, and then attaching them to a table which previously had 
CREATE INDEX ... ONLY ON executed.

Can I do something similar on an existing table (for example, on a heavily 
partitioned table, or because I want to see that progress is being made)?

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