CST 363 - Week 5

The web site "Use the Index Luke" has a page on "slow indexes". https://use-the-index-luke.com/sql/anatomy/slow-indexes

If indexes are supposed to speed up performance of query, what does the author mean by a slow index?


Because databases are supposed to speed up performance, many people have concerns when they don't return data as quickly as expected. A "slow index" is the name given when this occurs. The myth of the slow index was originated by the idea that an index search simply traverses the tree, but in reality it requires multiple steps of the tree traversal, following the leaf node chain, and fetching the data from the table. For the tree traversal, the index lookup will act quickly, but for the other two steps, they are potentially accessing many blocks while trying to ensure accurate matching, which will slow down the index lookup.