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Dimension groups

A dimension group unites dimensions that describe the same object and corresponds to a dimension table in the database. It defines the set of dimensions, their order, and the primary key through which the dimension table is linked to fact tables. Dimension groups are managed on the Dimension groups tab of the RMD screen.

Columns in the RMD table with dimension groups

Column name Column description
Name A text field for the business name of the dimension group
Description A text field for a short description of the dimension groups's purpose and meaning
Dimensions An automatically populated field with the list of dimensions belonging to the dimension group
Primary key A dropdown list to select the exact database table column (field) to be used as the primary key, through which the dimension group is linked to fact tables
Related fact tables An automatically populated field with the list of fact tables related to the dimension group

Every column of the list supports sorting and search. New portions of the list are loaded as you scroll. If the project version has no dimension groups, the tab shows Dimension groups not found together with the action that creates one.

Error indicators in the list

Indication Meaning
Warning icon next to the name The group uses dimensions that have errors
Warning icon on a dimension This dimension has errors
Error text in Primary key The primary key cannot be used: the connected source is not configured in the RMD, the connection has been deleted or is not connected, the column no longer exists, or the stored source has an invalid format

Creating a dimension group

  1. Click Add dimension group on the Dimension groups tab
  2. Fill in Dimension group name and, if needed, Dimension group description
  3. Choose the Primary key
  4. Add the dimensions of the group and arrange them
  5. Click Save

Name and description:

  • The name is required, must be unique among the dimension groups of the version, and can be up to 64 characters long
  • Allowed characters in the name are Latin and Cyrillic letters, digits, spaces, dots, hyphens, and underscores. A name cannot start with a special character
  • The description is optional and can be up to 255 characters long

Primary key

The primary key is the column of the dimension table that the fact tables refer to. It is chosen as a cascade:

  1. Connection
  2. Table, shown together with its schema as schema.table
  3. Column

The selected key is displayed as connection / schema.table / column. This key must correspond to the primary key of the dimension table in the database — SQL generation for fact tables and data marts relies on it. On the fact table side, the column that refers to this key is configured on the Relationships tab of the RMD screen (see the Fact tables section).

Dimensions of a group

The dialog has two lists:

  • Available dimensions — the dimensions of the project version. The list can be sorted and searched
  • Dimensions in dimensions group — the dimensions that the group consists of

A dimension is added by ticking its checkbox in the left list and removed by clearing the checkbox or by the delete control on its row in the right list. Both lists have an information icon next to a dimension that opens Details from RMD for it.

Notes:

  • A dimension can belong to one dimension group only. If the dimension you add already belongs to another group, the dialog warns that it will be moved to the new one
  • Dimensions whose names are duplicated in the RMD cannot be added — resolve the duplication on the Dimensions tab first
  • Dimensions with errors are marked in the lists

Order of dimensions

The dimensions in Dimensions in dimensions group are arranged by dragging them. The list is flat: one dimension cannot be nested into another, so there are no hierarchy levels inside a group.

The order you set is saved and used everywhere the dimensions of the group are shown: on the tab, in this dialog, in fact tables, on the data model canvas, in data marts, in the exported file, and in the public API.

Editing and deleting

  • Edit in the row of a dimension group opens the same dialog. Save asks for a confirmation first, because the change affects every element of the project version that uses this group
  • Delete in the row deletes the group after a confirmation. The references to it are cleared in the RMD, and the elements of the project version that used the group are affected, so check them afterwards

Roles

Creating, editing, and deleting dimension groups, as well as loading them from a file, requires the Developer role or above and a valid license. The Analyst and Viewer roles can view the list, open Details from RMD, and export the data.