Theoretical options for SJR

[danolivo]

Techniqiues:
2. INNER JOIN Elimination
3. OUTER JOIN Elimination
4. OUTER JOIN Elimination with DISTINCT

Which of these techniques implemented (or can be possible implemented with our approach)?

Advantages:

• Performance
• More precise cardinality estimation
• Less number of entities at the stage of optimizing

Disadvantages

• Overhead variants:

1. we have many self joins but no one can be removed
2. we have many joins, but no one SJ exist
3. pricey procedure of SJ elimination

See:

1. Implementation of Two Semantic Query Optimization Techniques in DB2 Universal Database
   https://www.researchgate.net/publication/221309776_Implementation_of_Two_Semantic_Query_Optimization_Techniques_in_DB2_Universal_Database
2. https://blog.jooq.org/join-elimination-an-essential-optimiser-feature-for-advanced-sql-usage/