Polymorphic links

Runtime-typed foreign keys — the 67 edges no static ERD can draw.

A Dynamic Link stores the target’s name while a companion field holds the target’s doctype. The pair behaves as a foreign key whose table is chosen at runtime, so these edges cannot be drawn in a static ERD — but they are load-bearing, especially for party handling and document back-references. 67 such fields exist in scope.

Entity	Module	Link field	Doctype held in
Accounting Dimension Detail	Accounts	`default_dimension`	`reference_document`
Advance Payment Ledger Entry	Accounts	`against_voucher_no`	`against_voucher_type`
Advance Payment Ledger Entry	Accounts	`voucher_no`	`voucher_type`
Allowed Dimension	Accounts	`dimension_value`	`accounting_dimension`
Appointment	CRM	`party`	`appointment_with`
Asset Movement	Assets	`reference_name`	`reference_doctype`
Authorization Rule	Setup	`master_name`	`customer_or_item`
Bank Account	Accounts	`party`	`party_type`
Bank Guarantee	Accounts	`reference_docname`	`reference_doctype`
Bank Transaction	Accounts	`party`	`party_type`
Bank Transaction Payments	Accounts	`payment_entry`	`payment_document`
Bank Transaction Rule	Accounts	`party`	`party_type`
Bank Transaction Rule Accounts	Accounts	`party`	`party_type`
Batch	Stock	`reference_name`	`reference_doctype`
Contract	CRM	`document_name`	`document_type`
Contract	CRM	`party_name`	`party_type`
Email Campaign	CRM	`recipient`	`email_campaign_for`
Exchange Rate Revaluation Account	Accounts	`party`	`party_type`
GL Entry	Accounts	`against_voucher`	`against_voucher_type`
GL Entry	Accounts	`party`	`party_type`
GL Entry	Accounts	`voucher_no`	`voucher_type`
Journal Entry Account	Accounts	`advance_voucher_no`	`advance_voucher_type`
Journal Entry Account	Accounts	`party`	`party_type`
Journal Entry Account	Accounts	`reference_name`	`reference_type`
Journal Entry Template Account	Accounts	`party`	`party_type`
Landed Cost Item	Stock	`receipt_document`	`receipt_document_type`
Landed Cost Purchase Receipt	Stock	`receipt_document`	`receipt_document_type`
Loyalty Point Entry	Accounts	`invoice`	`invoice_type`
Maintenance Visit Purpose	Maintenance	`prevdoc_docname`	`prevdoc_doctype`
Opportunity	CRM	`party_name`	`opportunity_from`
Party Link	Accounts	`primary_party`	`primary_role`
Party Link	Accounts	`secondary_party`	`secondary_role`
Party Specific Item	Selling	`based_on_value`	`restrict_based_on`
Party Specific Item	Selling	`party`	`party_type`
Payment Entry	Accounts	`party`	`party_type`
Payment Entry Reference	Accounts	`advance_voucher_no`	`advance_voucher_type`
Payment Entry Reference	Accounts	`reference_name`	`reference_doctype`
Payment Ledger Entry	Accounts	`against_voucher_no`	`against_voucher_type`
Payment Ledger Entry	Accounts	`party`	`party_type`
Payment Ledger Entry	Accounts	`voucher_no`	`voucher_type`
Payment Order Reference	Accounts	`reference_name`	`reference_doctype`
Payment Request	Accounts	`party`	`party_type`
Payment Request	Accounts	`reference_name`	`reference_doctype`
Process Payment Reconciliation	Accounts	`party`	`party_type`
Process Statement Of Accounts	Accounts	`collection_name`	`customer_collection`
Purchase Invoice Advance	Accounts	`reference_name`	`reference_type`
Quality Feedback	Quality Management	`document_name`	`document_type`
Quality Inspection	Stock	`reference_name`	`reference_type`
Quality Meeting Minutes	Quality Management	`document_name`	`document_type`
Quotation	Selling	`party_name`	`quotation_to`
Quotation Item	Selling	`prevdoc_docname`	`prevdoc_doctype`
Repost Accounting Ledger Items	Accounts	`voucher_no`	`voucher_type`
Repost Item Valuation	Stock	`voucher_no`	`voucher_type`
Repost Payment Ledger Items	Accounts	`voucher_no`	`voucher_type`
Sales Invoice Advance	Accounts	`reference_name`	`reference_type`
Serial No	Stock	`reference_name`	`reference_doctype`
Serial and Batch Bundle	Stock	`voucher_no`	`voucher_type`
Service Level Agreement	Support	`entity`	`entity_type`
Stock Ledger Entry	Stock	`voucher_no`	`voucher_type`
Stock Reservation Entry	Stock	`from_voucher_no`	`from_voucher_type`
Stock Reservation Entry	Stock	`voucher_no`	`voucher_type`
Subscription	Accounts	`party`	`party_type`
Tax Withholding Entry	Accounts	`party`	`party_type`
Tax Withholding Entry	Accounts	`taxable_name`	`taxable_doctype`
Tax Withholding Entry	Accounts	`withholding_name`	`withholding_doctype`
Unreconcile Payment	Accounts	`voucher_no`	`voucher_type`
Unreconcile Payment Entries	Accounts	`reference_name`	`reference_doctype`

The recurring patterns:

Pattern	Fields	Used for
Party	`party_type` + `party`	Payment Entry, GL Entry, Payment Ledger Entry — a party is a Customer, Supplier, Employee or Shareholder.
Reference	`reference_doctype` + `reference_name`	Linking a payment, journal row or ledger entry back to the document that caused it.
Against voucher	`voucher_type` + `voucher_no`	Stock Ledger Entry and GL Entry pointing at their originating transaction.
Link	`link_doctype` + `link_name`	Address and Contact attachment to any party.
Allocation	`allocated_to_doctype` + `allocated_to`	Serial/batch and reservation allocation.