Contents Index Predicate analysis Unnecessary DISTINCT elimination

ASA SQL User's Guide
  Query Optimization and Execution
    Semantic query transformations

Types of semantic transformations


The optimizer can perform a number of transformations in search of more efficient and convenient representations of your query. Because the optimizer performs these transformations, the plan may look quite different from a literal interpretation of your original query. Common manipulations include:

The following subsections discuss each of these operations.


Unnecessary DISTINCT elimination
Subquery unnesting
Predicate pushdown into GROUPed or UNION views
Join elimination
Optimization for minimum or maximum functions
IN-list optimization
LIKE optimizations
Conversion of outer joins to inner joins
Discovery of exploitable conditions
Elimination of unnecessary case translation

Contents Index Predicate analysis Unnecessary DISTINCT elimination