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Grantor_name is the user who grants the privileges.
Principal_name is the target which grantor grants privileges to.
The value of principal_type are USER or ROLE.
Collection_priv is the privilege to a collection, like SELECT, INSERT, UPDATE, etc.
For some collections which have alias, it will first get the real collection of the alias. Privilege verification will be based on the real collection not the alias. Collections stored in the privileges table are also the real collection, not the alias.
7、Privileges of resource DATABASE (Not used now)
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