Minimizing partitions

By default, Vertica supports up to 1024 ROS containers to store partitions for a given projection (see Projection parameters). A ROS container contains data that share the same partition key, or the same partition group key. Depending on the amount of data per partition, a partition or partition group can span multiple ROS containers.

Given this limit, it is inadvisable to partition a table on highly granular data—for example, on a TIMESTAMP column. Doing so can generate a very high number of partitions. If the number of partitions requires more than 1024 ROS containers, Vertica issues a ROS pushback warning and refuses to load more table data. A large number of ROS containers also can adversely affect DML operations such as DELETE, which requires Vertica to open all ROS containers.

In practice, it is unlikely you will approach this maximum. For optimal performance, Vertica recommends that the number of ungrouped partitions range between 10 and 20, and not exceed 50. This range is typically compatible with most business requirements.

You can also reduce the number of ROS containers by grouping partitions. For more information, see Partition grouping and Hierarchical partitioning.