CHAPTER 29 SECURING POSTGRESQL w: Stands (Multiple domain web hosting)
CHAPTER 29 SECURING POSTGRESQL w: Stands for write and represents UPDATE privileges. d: Stands for delete and represents DELETE privileges. R: Stands for rule and allows the user to create or drop rules on the given relation. x: For the REFERENCES privilege. Users with this privilege can create foreign keys from other tables that reference the relations in question. t: For the TRIGGER privilege. Users with this privilege can create and drop triggers on the given relation. An entry within the relacl column comprises one or more of the preceding attributes preceded with user information to create a complete privilege entry. If the user portion is left blank, the privileges listed are granted to PUBLIC, or all, users. In later versions of PostgreSQL, these entries are followed by a /username portion that signifies who granted the permissions in the entry. Let s take a look at a few examples: The first example demonstrates SELECT, INSERT, and UPDATEprivileges for user rob, granted by user dylan: rob=raU/dylan The next example shows SELECT privileges for PUBLIC, granted by the Postgres superuser: =r/postgres Finally, this example demonstrates full privileges for user dylan, granted by user dylan, and INSERT and UPDATE privileges for PUBLIC, granted by user dylan: {dylan=arwdRxt/dylan,=aw/dylan} Note The owner of an object gets full privileges by default. However, these privileges are not displayed in the relacl column by default. Instead, they become visible only when they have been explicitly granted by someone. User and Privilege Management While the privilege information can be read from the pg_class table just like any other table in PostgreSQL, for the purposes of manipulating it, you would not want to have to construct cumbersome arrays to update those values. Instead, PostgreSQL supports several SQL commands that you can use to add, update, and drop users, groups, and the various privileges those users might need. Working with PostgreSQL Users PostgreSQL gives us several SQL-level commands to create users and groups, thus defining their roles within the database system: CREATE USER, ALTER USER, and DROP USER for manipulating users, and CREATE GROUP, ALTER GROUP, and DROP GROUP for manipulating groups.
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