Two comments added in this branch cite docs-prd/008-.../数据库变更.md by path.
That directory is not tracked here, so the citation reads as a file the reader
can open and cannot. The reasoning it pointed at is short enough to state in
place.
Three comments from the previous batch cite the same path and are left alone;
they belong to a different change.
`migrate install <code>` brings one application up to the version its manifest
declares: it runs that application's outstanding migrations and records what
it did in sys_app.
It goes under migrate rather than under the existing `app` command, which
already means "generate the skeleton of a new application" - a directory that
does not exist yet, not an application already compiled into this binary.
Installing one is running its migrations, which is what this command is, so
--domain, resolveDB and the guard that refuses a mistyped code instead of
reporting a successful no-op are all already here.
Three phases, each committing on its own, and they are not one transaction.
An application's versions are separate migration files, and on MySQL a DDL
statement commits the transaction around it - destroying an outer transaction
and every savepoint taken from it. So this does not promise that a
half-installed application cannot happen. It promises one is visible when it
does: phase A writes "installing" before anything that can fail, phase B runs
the migrations, phase C turns that into "installed" or into "failed" with the
version it stopped on.
What is left to apply comes from sys_migration, never from sys_app. sys_app
is a derived view - a summary, and the answer to "which version does this app
think it is at". If it were the authority, an operator who deleted
sys_migration rows by hand would be told an application is installed while its
schema is not, which is worse than not knowing. So "already installed, nothing
to do" needs all three: nothing outstanding, recorded as installed, and the
same version. A row stuck at "installing" - what it reads as after the process
was killed partway - is not installed, and retrying is just running the
command again.
An upgrade is in place and keeps the first install's time; a downgrade is
refused, and refused before phase A writes anything, so a refusal cannot cost
the operator the row that told them what they had. An unparseable recorded
version is refused the same way, while it is still readable.
The report ends by saying the code is not running yet. That is not a
pleasantry: Go links at build time and Vite resolves its import globs at build
time, so installing an application writes its menus, its APIs and its
permissions and cannot make one line of its code run - and the menus appearing
is exactly what makes an operator believe otherwise.
Ten degradations were applied one at a time to check the tests name the
behaviour rather than the shape: deciding the no-op from sys_app alone,
always writing installed_at, allowing the downgrade, keeping the previous
attempt's diagnostics on a row that now says installed, treating "installing"
as installed, truncating last_error by bytes so a Chinese message is cut
mid-rune, not recording the failure at all, skipping code normalization, and
writing phase A before either the downgrade or the version-parse refusal.
Each went red on the assertion it was aimed at. An eleventh was discarded
rather than counted: it failed in the first install's setup, not on the claim.
sys_app is one row per installed application. It is physically deleted
on uninstall rather than following the millisecond soft-delete marker
the other sys_ tables use: an installed-app registry has no "deleted by
accident, needs recovering" case, and a physical delete is what lets the
same code be installed again afterwards.
status is installing/installed/failed rather than a boolean, because an
install spanning several migration files is not atomic on MySQL - DDL
commits implicitly, so a run can stop in the middle. failed_version and
last_error are diagnostic snapshots for a person to read; nothing may
decide anything from them, and the field comments say so. Where to
resume is answered by sys_migration, which cannot drift from what was
actually applied.
sys_app_casbin_grant records which casbin_rule rows an install created,
keyed by casbin_rule's own natural key. That table is not extended
instead: gorm-adapter's SavePolicy truncates and reloads it from an
in-memory model, which would drop any column added here without a word.
Built against SQLite, MySQL 8.0 and PostgreSQL 15.
zhangwenjian