Start Stonebraker et al.

1
Start Stonebraker et al. Chap. 7

• Chap. 7 Rules
• O-R DBMS needs a powerful rule system
• Four types
• Update-update, query-update, update-query,
  query-query

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Stonebraker et al. Chap. 7

• Update-update
• Update event occurs and then action is another
  update
• Example on p. 102 next slide

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UpdateUpdate Rules

• Create rule Mike_Jane_salary_synch
• on update to emp.salary
• where current.name Mike
• do update emp
• set salary new.salary
• where name Jane
• Update emp
• set salary 52500
• where name Mike
• (continue)

4

• Create rule Mike_Emma_salary_synch
• on update to emp.salary
• where current.name Mike
• (do update emp)
• set salary current.salary
• where name Emma
• Update emp
• set salary 56000
• Where name Mike

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Stonebraker et al. Chap. 7

• Query-update
• Query event and then update action
• Example on p. 103 next slide

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Query-Update Rules

• Create rule audit_salary_review
• on select to emp.salary
• where current.name Mike
• do insert into audit
• values
• (current.salary, user, current_datetime)

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Stonebraker et al. Chap. 7

• Update-query
• Event is update and then generate a response to
  user
• alert
• p. 104 for example next slide
• Can have listener or poll condition

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Update-Query Rules

• Create alert alert_Mike_on_salary_review
• (mechanism callback)
• Create rule alert_Mike_on_salary_change
• on update to emp
• where current.Name Mike
• do raise alert alert_Mike_on_salary_review

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Stonebraker et al. Chap. 7

• Query-query
• Event is retrieval and then action is retrieval
• Instead command
• See p. 105 for example next slide
• Can be made to lie to unauthorized users.

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Query-Query Rules

• Create rule Jane_Mike_salary_synch
• on select to emp.salary
• where current.name Jane
• do instead
• select salary from emp
• where name Mike

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Stonebraker et al. Chap. 7

• Bad part of rules
• Multiple rules can fire and results become
  unpredictable
• Infinite loops
• Abort of transaction also aborts action on rule
  (eg. Audit trail fails)
• State of database

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Stonebraker et al. Chap. 7

• Summary
• Feature 1 rule system to support events and
  actions both updates and retrieves
• Feature 2 rule system integrated with other O-R
  capabilities
• Feature 3 see next slide
• Feature 4 no looping

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• 3 - A rule system supports immediate, deferred
  and same transaction, different transaction
  execution semantics.

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Stonebraker et al. Chap. 7

• Give an example of a rule you could use in your
  database

15
Stonebraker and Brown

• Feature 8 - Open Storage Manager
• Open interface where third parties (not DBMS)
  can write storage managers
• DBMS has access to specialized storage manager

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Stonebraker and Brown

• Stonebrakers vision