# Optimized Indexes Selection

+ Extracting access conditions for the given index
  + The filtering criteria can be varied: CNF vs DNF
  + Choosing a single-column index or a composite index
  + Indexes cannot have false-negative misjudgments
  + Index Merge access
+ Merge and convert access conditions
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Ranger module for index selection
- Access conditions for the given index extraction
  - The filtering conditions can be varied (CNF vs. DNF)
  - Select a single-column index or a composite index
  - Index must not have false-negative misjudgment
  - Index Merge access
- Merge and convert access conditions