Add inheritance module: SINGLE_TABLE vs JOINED vs TABLE_PER_CLASS on Hibernate 7.4.13.Final

Same payment hierarchy mapped three ways plus @MappedSuperclass, run with plain Hibernate on H2. Tests assert and write the generated DDL, the INSERT/SELECT SQL, row/insert/FK/nullability counts and the three failures (NOT NULL on a SINGLE_TABLE subclass column, IDENTITY with TABLE_PER_CLASS, querying a @MappedSuperclass); Bench writes indicative polymorphic-query timings. No docs folder: depth lives in the post.
2026-10-24 10:02:28 +00:00
parent 833f3e1c31
commit 807f681ed1
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+Hibernate 7.4.13.Final, H2 in memory
+
+== SINGLE_TABLE
+INSERT statements to save 3 payments + 1 order: 4
+tables and row counts:
+  st_order = 1
+  st_payment = 3
+IS_NULLABLE for card_last4 in st_payment: YES
+foreign keys on st_order: 1
+
+discriminator values stored: [BANK, CARD, WALLET]
+raw INSERT of a CARD row with no card_last4: Check constraint violation: "ST_PAYMENT_SUBCLASS_COLUMNS: "; SQL statement:
+insert into st_payment (id, amount, currency, payment_type) values (900, 1.00, 'EUR', 'CARD') [23513-240]
+
+== JOINED
+INSERT statements to save 3 payments + 1 order: 7
+tables and row counts:
+  jn_bank_transfer_payment = 1
+  jn_card_payment = 1
+  jn_order = 1
+  jn_payment = 3
+  jn_wallet_payment = 1
+IS_NULLABLE for card_last4 in jn_card_payment: NO
+foreign keys on jn_order: 1
+
+== TABLE_PER_CLASS
+INSERT statements to save 3 payments + 1 order: 4
+tables and row counts:
+  tp_bank_transfer_payment = 1
+  tp_card_payment = 1
+  tp_order = 1
+  tp_wallet_payment = 1
+IS_NULLABLE for card_last4 in tp_card_payment: NO
+foreign keys on tp_order: 0
+
+== SINGLE_TABLE with nullable = false on subclass columns
+IS_NULLABLE: [A_VALUE | NO, B_VALUE | NO, ID | NO, KIND | NO]
+persist(new SnA()): org.hibernate.exception.ConstraintViolationException: could not execute statement [NULL not allowed for column "B_VALUE"; SQL statement:
+insert into sn_root (a_value,kind,id) values (?,'A',?) [23502-240]] [insert into sn_root (a_value,kind,id) values (?,'A',?)]
+
+== TABLE_PER_CLASS with GenerationType.IDENTITY
+org.hibernate.MappingException: Cannot use identity column key generation with <union-subclass> mapping for: com.ankurm.inheritance.TpcIdentityCard
+
+== querying a @MappedSuperclass
+tables: [mp_invoice, mp_receipt]
+org.hibernate.query.sqm.UnknownEntityException: Could not resolve root entity 'AuditedBase'