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Summary

Rollover bundles are used to enable transfer of remaining free units from one period to another subsequent period. The purpose of this document is to describe how this functionality is implemented as part of the core project.

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Design and Implementation

The starting point of the design was the fact, that a subscription bundle has to work in two contexts:

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• VALUE_1 - maximum number of units inside available for current subscription bundle ,period.
• VALUE_2 - total number of units used of current subscription bundle period, i.e. the sum of units used by the subscription bundle itself and by other subscription bundles bundle periods (when the bundle is used as a surplus bundle),.
• VALUE_3 - maximum number of units that can be rolled over (, i.e. the maximum number of units that can be used as surplus by other subscription bundles)bundle periods. As this value indicates a part of value_1, it will not make sense to have a number greater than value_1.
• VALUE_4 - total number of units used by rolloverother subscription bundle periods. Value cannot exceed value_3. Note that value_4 is not a simple value, it is used as "a value from which other information can be calculated" (for more information, see below).

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The difference between value_3 and value_4 (i.e. value_3 - value_4) is supposed to indicate how many units are available for rollover.

This means that every time units are used (i.e. some value is added to value_2), also value_4 is likewise increased with the same number of units, as this now indicates that less units are available for rolloverfor the current subscription bundle period, value_4 is not updated unless the number of free units (value_1 - value_2) exceeds the rollover limit (value_3). In this case value_4 is decreased to ensure the available rollover units do not exceed the number of free units.

The rules for how/when to update value_4 are:

• When the bundle is used as a surplus bundle by another bundle, then value_4 is updated with the amount of units used by that other bundle.
  • Note that the process that updates value_4 shall make sure to also update value_2 with the same amount of units.
• When value_2 is updated it needs to be checked if the total units available in the bundle is now less than the number of units that can be used as surplus. If this is the case, then value_4 needs to be updated such that this is no longer the case.
  • In more mathematical terms, if (value_1-value_2)<(value_3-value_4), then adjust value_4 such that the '<' becomes '='. This means that value_4 shall be set equal to value_3-(value_1-value_2).

ExamplesExample how value_4 is used for current period

Suppose a bundle has value_1 = 500, value_3 = 200. This means the bundle has 500 units for charges in actual period, from which 200 units may be used by charged charges from other periods.

Suppose now that 190 units have been used in a period, i.e. value_2 = 190 and value_4 = 190.

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Lets assume a subscription bundle is created initially and some usage is added to this subscription bundle period:

Example how value_4 is used for rollover periods

Now lets assume a subscription bundle is created initially but no usage is added for the subscription bundle period. Now the subscription bundle period is used by another period using rollover functionality:

Note, the last usage may actually be higher than 30, however the actual subscription bundle do only allow usage up to 30 units to be handled.

Example how value_4 is used for combined usage in current and rollover periods

Subscription Bundle Update Manager

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Migration of existing subscription bundles

When existing bundles are re-configured to have rollover functionality then the existing subscription bundles need to be updated.

First initialize the field for the max rollover.

update subscription_bundle set value3 = (select value3 from bundle b where 
b.id = subscription_bundle.bundle_id) where
exists (select * from bundle b where b.id = subscription_bundle.bundle_id and 
b.parameters like '%UPDATE_MANAGER=ROLLOVER%');

Next set the field for used rollover units. If this one (value4) has a value (other than 0) then it is because the usage (value2) started leaching of the amount that can be rolled over. Value4 is the excess amount past value1-value3.

update subscription_bundle set value4=case when value2 > (value1-value3) then 
value2 - (value1-value3) else 0 end where
exists (select * from bundle b where b.id = subscription_bundle.bundle_id and 
b.parameters like '%UPDATE_MANAGER=ROLLOVER%');