uk_sys_menu_app_seed_code_del covers (app_code, seed_code, deleted_at) and is
created by 1786700008000 with explicit SQL. The struct tag named the same
index on SeedCode alone, and a named uniqueIndex tag collects only the fields
carrying that name - so AutoMigrate on this model would build a unique index
on seed_code by itself: stricter than the real one, and forbidding two
applications from both having a "dir" node, which the composite key exists to
allow.
Worse than being stricter, it would win. The migration only creates its index
when HasIndex says the name is free, so a schema built by AutoMigrate first
keeps the wrong index and the migration steps over it without a word.
The tag cannot express the real index: deleted_at comes from the ModelTime
embed shared by every table, which no single model can add a tag to. So the
tag goes and the migration is the only thing that creates it.
No database is affected. The initial table migration AutoMigrates a frozen
snapshot of this model that has neither app_code nor seed_code, and nothing
else in the repository AutoMigrates the live one - which is why this stayed
invisible until a test built the schema from the live model and seeded two
applications, and got a unique-constraint failure on a seed code they are
supposed to be able to share.
Seeding needs something to look for before it inserts, or a retry writes
a second copy of everything it already wrote. sys_api already had one in
(app_code, path, action). sys_menu had nothing usable: menu_name is
pascalCase(appCode) + pascalCase(code), which is not injective -
"list-all", "listAll" and "list_all" all become "ListAll" - so the
original code cannot be recovered from it. Hence a new column.
seed_code is nullable, against this repository's habit of NOT NULL
DEFAULT '' for a new column, and deliberately. Every row that predates
it has no meaningful value, and under a unique index an empty string
collides with every other empty string while NULL collides with nothing.
The convention exists because deleted_at's nullability broke a unique
index; here nullability is what makes one possible.
The unique index on sys_api cannot simply be created: a live database is
known to hold historical duplicates - the demo site had eighteen. The
migration looks first and refuses while naming the offending rows,
rather than letting CREATE UNIQUE INDEX fail with a constraint error
that names none. Same shape as 1786700003000's refuseOnDuplicates.
Run against SQLite, MySQL 8.0 and PostgreSQL 15, including the CONCAT
duplicate check, which had only ever been executed by SQLite's driver.
sys_migration already carries app_code; sys_menu and sys_api did not, so
nothing said which application seeded a row - which is what an uninstall or
an audit would have to ask.
The migration adds the columns through the runtime models rather than
cmd/migrate/migration/models, whose frozen ModelTime is wrong for anything
ordered after the soft-delete conversion.
Claude-Session: https://claude.ai/code/session_01HPTAw8b8tAdFNFn8rKdPYx
zhangwenjian