3. Assigning Privileges and Granting Permissions : Grant Overhead
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Grant Overhead
Grants can affect query processing time. Queries for a table or view have overhead if:
Permissions have been granted on the table or view
Column-specific permissions are granted
Many permissions are granted in general in the database
For the following, however, there is no overhead:
For the table owner
On certain public grants:
In select operations
Any operation for which all allowed permissions are specified for public
If no permissions qualify (the query is simply aborted)
There is additional overhead during session initialization to evaluate database privileges for the authorization identifiers associated with the session. Because session initialization must read the catalogs in which groups, roles, and database privileges are stored, certain operations issued by the DBA or system administrator that write to these catalogs can be committed or rolled back as soon as possible. These operations include:
Granting or revoking database privileges
Creating, altering, or dropping a group
Creating, altering, or dropping a role