How can I revoke execution of a PostgreSQL function?

All functions access is PUBLIC by default, this means that any role can execute it. To revoke execution, there are 2 steps required:

• Revoke function execution (foo in this case) from PUBLIC:

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revoke execute on function foo from public;

• Revoke execution from a particular role (anon in this case):

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revoke execute on function foo from anon;

Now anon should get an error when trying to execute the function:

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begin;
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set local role anon;
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select foo();
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ERROR:  permission denied for function foo