Table and Column Partitions (IQ)

A partition is a physical division of the contents of a database table, based on values in the column designated as the partition key, and allocated to a particular dbspace. You can override the allocation of values in certain columns by specifying column partitions.

Creating a Table Partition

In order to create table partitions, you must first select a column as the Partition key on the Sybase IQ tab of the table property sheet (see Sybase IQ), in order to display the Partitions tab.

You can create as many partitions as necessary for the table on this tab using the Insert Row and Add a Row tools.

Note: Some PowerDesigner features automate the creation of partitions (see Denormalizing Tables and Columns and Modeling a Lifecycle. If you associate a table with a lifecycle (see Lifecycles (PDM)), PowerDesigner will delete all existing table partitions in order to create the necessary partitions to move data between lifecycle phases.

Table Partition Properties

To view or edit a partition's properties, double-click its Browser or list entry. The property sheet tabs and fields listed here are those available by default, before any customization of the interface by you or an administrator. The following properties are available on the General tab:

Property	Description
Parent object	[read only] Specifies the table of which the partition forms a part.
Name/Code/Comment	Identify the object. The name should clearly convey the object's purpose to non-technical users, while the code, which is used for generating code or scripts, may be abbreviated, and should not normally include spaces. You can optionally add a comment to provide more detailed information about the object. By default the code is generated from the name by applying the naming conventions specified in the model options. To decouple name-code synchronization, click to release the = button to the right of the Code field.
Stereotype	Extends the semantics of the object. You can enter a stereotype directly in this field, or add stereotypes to the list by specifying them in an extension file.
Values	Specifies the upper bound of the partition, based on the value of the column specified as the partition key. The `max` keyword can only be set on the last partition.
DBSpace	Specifies the dbspace with which the partition is associated (see Dbspaces (IQ)). Select a dbspace from the list or click the tools to the right of this field to create, delete, or search for a dbspace, or to open the property sheet of the selected dbspace.

Overriding Partition DBspaces for a Particular Column

You can override the allocation of values in a particular column from the table partition dbspace to an alternate dbspace. The column will continue to be partitioned based on the same partition key ranges, but the column values for each range will be allocated to the alternate dbspaces.

You create column partitions on the Partitions tab of the column property sheet. Click the Properties tool to specify the following properties:

Property	Description
Parent object	[read only] Specifies the column to which the partition belongs.
Comment	Provides more detailed information about the object.
Partition	Specifies the table partition for which this partition will redirect column values to an alternate dbspace.
Dbspace	Specifies the dbspace (see Dbspaces (IQ)) to which column values contained within this table partition should be allocated.