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A partition is a division of a logical database or its constituting elements into distinct independent parts.
Database partitioning is normally done for manageability, performance or availability reasons.
The partitioning can be done either building separate smaller databases (each with its own tables, indexes, and transaction logs), or by splitting selected elements, for example just one table.
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
zipcodehas a value between70000and79999. - 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
Countryis eitherIceland,Norway,Sweden,FinlandorDenmarkcould 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.
See also
External links
"Partition (database)"