These modeling features have a different behavior, or are not available, in Polaris.

FeatureDescription
BreakbackSet Breakback on line items.
Brought forwardSet Brought forward on a line item.
Drilldown

Display the formulas and data references calculated for a cell's value.

In Polaris, only evaluated expressions display for drilldown. For example, only the condition and chosen branch of an IF THEN ELSE clause display for drilldown.

Switchover

The behavior of Switchover in Polaris differs from Classic regarding data preservation. The current Polaris implementation keeps the primary data from before switchover, when it's enabled. This means data reappears when Switchover is disabled. This feature shouldn't be relied upon as a model building practice.

Switchover behavior may change in future releases and Anaplan does not guarantee this behaviour remains the same.

Optimizer actionCreate an Optimizer action.
Summary methodsCalculate child cells into a single value using a combination of aggregate and formula-based summaries. 
Tabular single column exportExport each dimension in a module as a separate column, with the final column containing data.
Time rangesCreate time ranges. See Time ranges in Polaris for considerations on its use with a sparse calculation engine. 
Workflow  Set the Workflow property on lists.
Year to Date and Year to GoInclude Year to Date and Year to Go time summaries in the Model Calendar. 
Tabular multiple column exportInclude a Boolean line item filter to limit exported module data in a multiple column layout. 
Formula reference to a line item subsetIn Polaris, a value from another line item subset can be stored in a line item with any line item subset format. However, where the stored value does not exist in the line item subset the format uses, the result is blank.

In the Classic Engine, the value from another line item subset is rejected instead, even if that line item value is also part of the line item subset the format uses. 
Line item dimensionality

In Polaris, a line item may support up to 63 dimensions having more than one item.

In the Classic Engine, the count of dimensions is limited by workspace size.

Line item count

In Polaris, a model may contain up to 10,000 line items.

In the Classic Engine, the count of line items is limited by workspace size.

Version count

In Polaris, a model may contain up to 100 versions.

In the Classic Engine, the count of versions is limited by workspace size.

List property count

In Polaris, a model may contain up to 10,000 list properties.

In the Classic Engine, the count of list properties is limited by workspace size.

Value of empty summariesIn Polaris, references to empty summaries take the default value of the data type. For example, 0 for Numbers, and FALSE for Booleans.

In the Classic Engine, references to empty summaries return the value of the corresponding cell.
Filters on empty summaries

In Polaris, empty summaries have no value, and do not show in filtered results.

In the Classic Engine, they have value and therefore can show in filtered results.

Sort on empty summaries

In Polaris, empty summaries take the default value of the data type, when sorting.

In the Classic Engine, sorting uses their calculated value.

Formula lengthIn Polaris, the maximum length of a formula is 2,000 characters. In the Classic Engine, there is no set limit.
Edit line items in composite listsIn Polaris, if a line item is dimensioned at a given level of a hierarchy, then higher level empty summaries have no value. Empty summaries at the given level are editable.

In the Classic Engine, the higher level empty summaries are evaluated, and depend on the datatype and the summary method. For example, 0 for SUM.
Exports and views

In Polaris, an error message displays if your export or view exceeds a row count or column count of 2,147,483,647.

In the Classic Engine, the view or export silently truncates.