Partitioning Criteria
Current high end relational database management systems provide for different criteria to split the database. They take a partitioning key and assign a partition based on certain criteria. Common criteria are:
- Range partitioning
- Selects a partition by determining if the partitioning key is inside a certain range. An example could be a partition for all rows where the column
zipcode
has a value between70000
and79999
. - List partitioning
- A partition is assigned a list of values. If the partitioning key has one of these values, the partition is chosen. For example all rows where the column
Country
is eitherIceland
,Norway
,Sweden
,Finland
orDenmark
could build a partition for the Nordic countries. - Hash partitioning
- The value of a hash function determines membership in a partition. Assuming there are four partitions, the hash function could return a value from 0 to 3.
Composite partitioning allows for certain combinations of the above partitioning schemes, by for example first applying a range partitioning and then a hash partitioning. Consistent hashing could be considered a composite of hash and list partitioning where the hash reduces the key space to a size that can be listed.
Read more about this topic: Partition (database)
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