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zhangwenjian
d43d7a46dd
1786700008000 could not be applied to any SQL Server database. Not an old one
with awkward data - any of them, including an empty one:
Msg 1505 ... duplicate key ... The duplicate key value is (, <NULL>, 0).
MySQL, PostgreSQL and SQLite treat two NULLs in a unique index as different
values, so any number of rows missing a seed_code coexist under
uk_sys_menu_app_seed_code_del. SQL Server treats them as equal and permits
exactly one. 1786700001000 seeds five menus and none of them has a seed_code,
so the second one already collides with the first. sys_api's index has the
same shape over two nullable columns, path and action.
On SQL Server the index is now filtered to the rows that carry a value, which
is what the other three engines do by not comparing their NULLs. The filter is
not added elsewhere: MySQL has no filtered index at all, and on PostgreSQL and
SQLite it would only restate what those engines already do.
Nothing that has applied this migration is affected, and no SQL Server
database can have.
Verified against SQL Server 2022. The migration completes; the filtered index
still rejects a second (order, dir) and still lets another app reuse "dir",
so filtering removed the NULL rows from the index rather than the index's
teeth. Two degradations turn that red: dropping the filter, and naming only
path in sys_api's - the second one needed a fixture row with a path and no
action, because rows missing both are excluded either way and the first
attempt at that degradation came out green.
There is also a control test asserting the unfiltered statement still fails on
this engine, so the first test is passing because of the fix rather than
because SQL Server turned out not to mind.