Kas saak selgitada indeksite fragmentatsiooni kontseptsiooni SQL andmebaasis ja kuidas see mõjutab jõudlust?

Fragmentation of indexes in SQL databases is a situation where the logical order of data in the index does not match their physical placement on the disk. This occurs due to frequent insert, update, and delete operations, which cause breaks and empty spaces within index pages.

Types of fragmentation:

• Internal fragmentation: when there is a lot of free space inside index pages, reducing data storage density.
• External fragmentation: when consecutive index pages are not physically adjacent, which impairs sequential read speed.

Impact on performance:

• The number of input/output operations increases, as data is read from different locations on the disk.
• Query execution that uses the index slows down, especially when scanning large ranges.

To reduce fragmentation, reorganization or rebuild operations on indexes are applied, which improve data access speed.