This PR adds `PRAGMA schema_version` to get the value of the schema-
version integer at offset 40 in the database header.
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Closes#1427
WalShared state can be shared without having to wrap everything with a
lock, and instead use atomics on some places and rwlock on others -- for
now.
## Results:
From:
----
Execute `SELECT 1`/limbo_execute_select_1
time: [34.125 ns 34.218 ns 34.324 ns]
Execute `SELECT 1`/sqlite_execute_select_1
time: [28.124 ns 28.254 ns 28.385 ns]
To:
----
Gnuplot not found, using plotters backend
Execute `SELECT 1`/limbo_execute_select_1
time: [31.919 ns 32.113 ns 32.327 ns]
Execute `SELECT 1`/sqlite_execute_select_1
time: [29.662 ns 29.900 ns 30.139 ns]
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.
Currently we have a Record, which is a dumb vector of cloned values.
This is incredibly bad for performance as we do not want to clone
objects unless needed. Therefore, let's start by introducing this type
so that any record that has already been serialized will be returned
from btree in the format of a simple payload with reference to payload.
Closes#1176
- Use `CheckpointResult::default()` instead of `CheckpointResult::new()`
- Correct WAL frame header salt and checksum handling
- Ensure frame ID is 1-based and adjust frame offset calculation
- Add `Default` implementation for `CheckpointResult`
- Use random values for WAL header salts
Currently we have a Record, which is a dumb vector of cloned values.
This is incredibly bad for performance as we do not want to clone
objects unless needed. Therefore, let's start by introducing this type
so that any record that has already been serialized will be returned
from btree in the format of a simple payload with reference to payload.
There are two bugs in #1085.
1. `find_free_cell` accesses non-existent free blocks and returns their
size to `allocate_space`. This is out of range access error. The fix is
to add a loop termination condition that stops it when we hit the end of
the blocks
2. This bug is caused by `find_free_cell` some how swallowing the blocks
with size `4 bytes`. So `compute_free_space` consistently undercounts by
`4 bytes`. I've refactored that part of the code to make sure 4 sized
block are not deleted.
I've also added a unit test which proves these fixes work and also added
a function called `debug_print_freelist` which prints all free blocks of
a page.
For now I've silenced the `overflow_page` tests.
Fixes#1085Closes#1111
When I added frame reading support I thought, okay, who cares about the page id of this page it we read it from a frame because we don't need it to compute the offset to read from the file in this case. Fuck me, because it was needed in case we read `page 1` from WAL because it has a differnt `offset`.
Beep boop.
What happened you ask? I removed the dumb balancing algorithm I
implemented in favor of SQLite's implementation based on B*Tree[1] where
a page is 2/3 full instead of 1/2. It also tries to balance a page by
taking a maximum 3 pages and distributing cells evenly between them.
I've made some changes that are somewhat related:
* Moved most operations on pages out of BTreeCursor because those
operations are based on a page, not on a cursor, and it makes it easier
to test.
* Fixed `write_u16` and `read_u16` cases that didn't need a implicit
offset calculation. Added: `write_u16_no_offset` and
`read_u16_no_offset` to counter this.
* Added some tests with fuzz testing too.
* Fixed some important actions like: `compute_free_space`,
`defragment_page` and `drop_cell`.
[1] https://dl.acm.org/doi/10.1145/356770.356776Closes#968
The SerialType::try_from() was pretty high up in CPU profiles so I asked
my dear friend Claude to optimize it away by using the serial type
integer value directly instead of constructing a fancy enumeration.
