Summary
Tree-structured indexes are ideal for range-searches, also good for equality searches.
ISAM is a static structure.
- Only leaf pages modified; overflow pages needed.
- Overflow chains can degrade performance unless size of data set and data distribution stay constant.
B+ tree is a dynamic structure.
- Inserts/deletes leave tree height-balanced; log F N cost.
- High fanout (F) means depth rarely more than 3 or 4.
- Almost always better than maintaining a sorted file.