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30c6b665f1
Android has no /tmp and hands an app no TMPDIR. Go's os.TempDir() falls
back to "/tmp" when the variable is unset, so every library in this
process that wants scratch space was being handed a path that has never
existed.
SQLite is the one that noticed, and it said so precisely:
W/yellowjacket: msg="champion index rebuild failed"
explore.search-index.error="populate champion fts: disk I/O error (6410)"
6410 is not a generic I/O error. `6410 & 0xff` is 10, SQLITE_IOERR, and
`6410 >> 8` is 25 -- SQLITE_IOERR_GETTEMPPATH. SQLite could not work out
where to put a temporary file. Two measurements on the device say why:
`ls -d /tmp` does not exist, and the app process's environment carries
no TMPDIR. A shell's does (/data/local/tmp), which is why this is easy
to miss from `adb shell`.
The cost was a silent performance cliff on the slowest device this app
runs on: `championReady` stayed false, so every Explore search took the
generic path over the whole 1,079,667-row index instead of the champion
subset, and the rebuild was re-attempted on every launch.
**The class is fixed rather than the statement.** The trigger is the
*size* of the work, not that query -- anything that spills fails the
same way there, so large sorts, large joins and VACUUM were all waiting
their turn. The repair belongs at the process's one answer to "where do
temporary files go".
`PRAGMA temp_store = MEMORY` was the alternative: cheaper, more local,
and a promise that every future spill fits in RAM on a phone. The
catalog is the largest thing in this app and that is not a promise
worth making silently.
UseTempDir sits beside UseHomeOverride and carries its two rules for
the same reasons. **An empty base is a no-op**, because that is what
application.Mobile.StoragePath() returns on desktop -- so this needs no
build tag and changes nothing off mobile, where /tmp is real. And **an
explicit TMPDIR wins**, so anyone who set one deliberately gets it;
nothing sets it on the platform this exists for. It needs no new Wails
API and no Java change: StoragePath() is already what YJ_HOME is
pointed at, and the directory goes under it.
Two things beyond the rename of a variable.
**Writability is probed, not assumed.** MkdirAll on an existing
unwritable directory succeeds, so without the probe this could set
TMPDIR to a directory nothing can use -- which is the same bug one
directory over, and just as quiet.
**It returns its error, and main logs it.** A temp directory that could
not be created is the same silent failure one step earlier. A failure
is not fatal: it leaves the platform's answer in place, which is what
every release before this one ran with. That log line is readable on
the platform only because of #160.
Verified on the reference device, where the same launch that used to
print the failure now prints:
I/yellowjacket: msg="champion index rebuilt"
explore.search-index.elapsed=6.496s
Closes #190