TransitionResult is an internal implementation detail that tells
an invocation of StateMachine::step() to continue looping, but it
is of no use to other callers.
For this reason, just return an IOResult from StateMachine::step()
which simplifies the result handling.
This is considerably simpler with 1 thread as we just try to yield
control when I/O happens and we only run io.run_once when all
connections tried to do some work. This allows connections to
cooperatively progress.
The new query combines multiple aggregate functions, plain columns,
arithmetic expressions, and aggregates wrapped in additional expressions.
Local run results:
```
Prepare `SELECT first_name, last_name, state, city, age + 10, LENGTH(email), UPPER(first_name), LOWE...
time: [64.535 µs 64.623 µs 64.713 µs]
Found 9 outliers among 100 measurements (9.00%)
4 (4.00%) high mild
5 (5.00%) high severe
```
synchronous=FULL means WAL is fsynced on every commit,
which is what we also do.
however we do not do the padding to sector alignment that
sqlite does (see #2450), which makes sqlite do more work
than we do.
Makes it easier to test the feature:
```
$ cargo run -- --experimental-indexes
Limbo v0.0.22
Enter ".help" for usage hints.
Connected to a transient in-memory database.
Use ".open FILENAME" to reopen on a persistent database
limbo> CREATE TABLE t(x);
limbo> CREATE INDEX t_idx ON t(x);
limbo> DROP INDEX t_idx;
```
The logging code that writes out transactions to disk needs to write out
the byte array that we actually use. The code is less hairly without the
generics so drop them.
Move result row to `ProgramState` to mimic what SQLite does where `Vdbe`
struct has a `pResultRow` member. This makes it easier to deal with result
lifetime, but more importantly, eventually lazily parse values at the edges of
the API.
Fixes the following panics:
Benchmarking Execute `SELECT * FROM users LIMIT ?`/Limbo/100: Profiling
for 5.0000 sthread 'main' panicked at core/benches/benchmark.rs:69:43:
called `Result::unwrap()` on an `Err` value: IOError(Os { code: 4, kind:
Interrupted, message: "Interrupted system call" })
note: run with `RUST_BACKTRACE=1` environment variable to display a
backtrace
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Closes#882
