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A commission line is the resolved commission for one line item or one shipping method of an order. It’s derived data: Mercur computes it from the current rates and the order’s contents, writes it at checkout, and rewrites it whenever the order changes. Payouts read these lines to work out what the seller receives.

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What a line records

A line is a CommissionLine record (id prefix comline). It points at exactly one of item_id or shipping_method_id, and it stores the rate it came from and the amount.
The fields carry these values from the system provider:
  • code: the code of the winning rate, kept so the line stays readable if the rate is renamed or deleted
  • rate: the percent for a percentage rate, or the fixed amount for a fixed rate
  • amount: the commission for the line, computed with MathBN
  • description: Shipping Commission on shipping lines, empty on item lines
  • provider_id: the provider that computed the line, system by default
  • data: free JSON a custom provider can fill

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When lines are written

Mercur writes lines at checkout and rewrites them when the order’s contents change. Both paths run refreshOrderCommissionLinesWorkflow: A refresh resolves against the rates that exist when it runs. Changing a rate doesn’t touch existing lines until the order is refreshed again.

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A refresh replaces, it doesn’t append

Computed lines carry no id. The module’s upsertCommissionLines first deletes every existing line whose item_id or shipping_method_id is in the new set, then inserts the new lines in the same transaction. Running a refresh twice leaves one line per item and shipping method.
Deletion is keyed on the anchors in the new set. If an item no longer gets a line, for example because you disabled the only rate that matched it, its old line stays in place.

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How payouts use the lines

createOrderPayoutsWorkflow reads every commission line whose item_id or shipping_method_id belongs to the order. It sums their amount and pays the order total minus that sum to the seller’s payout account. A refund taken back later is reduced by its share of the same sum. With the lines from the overview figure, an order total of € 92.00 and commission of € 10.14 pays the seller € 81.86.