v2.20.0

Changed

• A cycle of CASCADE keys through several tables is enforced (#85, ADR 0041). It was refused while the cascade was an ON UPDATE rule, which PostgreSQL rewrites into itself; since 2.19.0 it is an arm of the owner's trigger, and an arm stops at _deleted_at IS NULL. Every project that declared one gets the arms: one archive stamps the whole loop it reaches, and a restore matches that stamp, so it travels up the loop too. A joined key into its own MTI root is enforced as well. soft_delete() and the .delete() fast path no longer decline a cycle edge. A cycle holding an owned key is still refused, with a note that no longer cites rule recursion. CascadeKind.CYCLE is gone and classify_cascade takes no cycle_edges. Existing projects: makemigrations (or makeguitarmigrations) writes a migration for each app hosting a cycle key, which replaces the owner's soft_delete_cascade_on_* trigger with one carrying the arms.
• A self-referential CASCADE key is an arm of the owner's trigger (#85, ADR 0042). It took a trigger of its own since 2.8.0, which stamped NOW() and never revived. It now carries the parent's _deleted_at and a restore revives the subtree archived with it; a child archived earlier keeps its own stamp. The primary-key-rewrite refusal is the union of the two (wider than the old trigger's for a statement that re-keys an archived row and also touches a live sibling with children), and a $$ in a name no longer refuses the key. makemigrations writes, for each app hosting a self key, a migration that replaces the owner's trigger and retires the self one, whose reverse rebuilds it (the owner's trigger, re-emitted, reverses to a DROP as every re-emission does). Existing projects: DROP TRIGGER takes ACCESS EXCLUSIVE on those tables until the migration commits, so set lock_timeout. Dropping a self key's column now fails an archive or a restore of the table until re-generated, not every UPDATE.