We make read_record faster by not allocating Vec if not needed. This is
why I introduced a simple `SmallVec<T>` that will have a stack allocated
list for the simplest workloads, and a heap allocated if we were to
require more stuff.
Both read_varint and read_value, at least in my mac m4, were not
inlined. Since these functions are called so many times it made sense to
inline them to avoid call overhead. With this I saw something like 20%
improvement over previous commit in my m4.
Improve allocation usage from ImmutableRecords by reusing them.
ImmutableRecord is basically a contigous piece of memory that holds the
current record. If we move to some other record we usually deallocate
the previous one and allocate a new one -- obviously this is wasteful.
With this commit we will reuse the ImmutableRecord to allow payload to
be extended if needed or reused if we can, making it faster to iterate
records basically.
Closes#1206Closes#447Closes#1117
Issues:
1. Rust floating point math fucntions are non deterministic.
2. SQLite have complex floating point display rules.
I changed rust functions to libm for math ops and implemented Display
trait for OwnedValue:Float. A lot of float formatting SQLite probably
inherits from C have to be handcrafted.
Closes#1208
This PR has two parts:
## 1. Make reading cells faster
My benchmark was simple, running `test_sequential_write` test and see
how long it takes. It is a nice benchmark because it will write a new
row and then `select * from t` for every write to check the contents.
## From:
```bash
cargo test test_sequential_write --release -- --nocapture --test-threads=1 7.21s user 0.34s system 88% cpu 8.527 total
```
### To:
```bash
cargo test test_sequential_write --release -- --nocapture --test-threads=1 3.14s user 0.31s system 82% cpu 4.161 total
```
## 2. Fix reading overflow pages.
The code to read overflow pages was wrong, `read_payload` would try to
read as many overflow pages as possible but if there weren't in cache
they would return `IO` and not read more pages after that. This PR makes
every read record to check if it needs to read from overflow pages and
if not, it will simply read from the current page.
Closes#1141
### The problem:
I often need to copy the output of an `Explain` statement to my
clipboard. Currently this is not possible because it currently will only
write to stdout.
All other limbo output, I am able to run `.output file` in the CLI, then
enter my query and in another tmux pane I simply `cat file | xclip -in
-selection clipboard`.
### The solution:
Expose a `statement.explain()` method that returns the query explanation
as a string. If the user uses something like `execute` instead of
prepare, it will default to `stdout` as expected, but this allows the
user to access the query plan on the prepared statement and do with it
what they please.
Closes#1166
Currently we can create two guards and unlock one of them and still have
two mutable references to the same data.
By being able to unlock only via guard we prevent unsafe scenarios.
Currently, the test below will pass and shows that we can hold two
mutable references to the same data. After this fix, this would result
in a deadlock (have to remove `lock.unlock()`)
```rust
#[test]
fn two_mutable_reference() {
let lock = SpinLock::new(42);
let guard = lock.lock();
lock.unlock();
let guard2 = lock.lock();
// two mutable references to same data
*guard = 10;
*guard2 = 20;
assert_eq!(*guard, 20);
assert_eq!(*guard2, 20);
}
```
Note: The javascript action failure is unrelated to this PR.
Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>
Closes#1194
