Postgres adapter raises error when using a copy to csv with a read replica (regression)

[Fivell]

Steps to reproduce

SlaveDb.connection.execute("COPY (select * from table_name) TO '#{file_path}.csv' WITH CSV HEADER;")

Expected behavior

it is possible to export data from replica database to csv file
COPY TO - readable sql
COPY FROM - writable sql
https://www.postgresql.org/docs/9.2/sql-copy.html

Actual behavior

The following error is raised: ActiveRecord::ReadOnlyError: Write query attempted while in readonly mode ...

System configuration

Rails version:
6.0.2.2
Ruby version:
2.5.5

[Fivell]

related #37960

[Fivell]

@eileencodes can you please comment on this? currently it was changed from
connection.execute to connection.raw_connection.exec to make this work

[rails-bot]

This issue has been automatically marked as stale because it has not been commented on for at least three months.
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