After reading #1123, I wanted to see what optimizations I could do.
Sqlite optimizes `count` aggregation for the following case: `SELECT
count() FROM <tbl>`. This is so widely used, that they made an
optimization just for it in the form of the `COUNT` opcode.
This PR thus implements this optimization by creating the `COUNT`
opcode, and checking in the select emitter if we the query is a Simple
Count Query. If it is, we just emit the Opcode instead of going through
a Rewind loop, saving on execution time.
The screenshots below show a huge decrease in execution time.
- **Main**
<img width="383" alt="image" src="https://github.com/user-
attachments/assets/99a9dec4-e7c5-41db-ba67-4eafa80dd2e6" />
- **Count Optimization**
<img width="435" alt="image" src="https://github.com/user-
attachments/assets/e93b3233-92e6-4736-aa60-b52b2477179f" />
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Closes#1443
This commit adds suport for DROP INDEX.
Bytecode produced by this commit differs from SQLITE's bytecode, main
reason we don't do autovacuum or repacking of pages like SQLITE does.
Closes#1280Closes#1444
The following code reproduces the leak (memory usage increases over
time):
```rust
#[tokio::main]
async fn main() {
let db = Builder::new_local(":memory:").build().await.unwrap();
let conn = db.connect().unwrap();
conn.execute("SELECT load_extension('./target/debug/liblimbo_series');", ())
.await
.unwrap();
loop {
conn.execute("SELECT * FROM generate_series(1,10,2);", ())
.await
.unwrap();
}
}
```
After switching to the system allocator, the leak becomes detectable
with Valgrind:
```
32,000 bytes in 1,000 blocks are definitely lost in loss record 24 of 24
at 0x538580F: malloc (vg_replace_malloc.c:446)
by 0x62E15FA: alloc::alloc::alloc (alloc.rs:99)
by 0x62E172C: alloc::alloc::Global::alloc_impl (alloc.rs:192)
by 0x62E1530: allocate (alloc.rs:254)
by 0x62E1530: alloc::alloc::exchange_malloc (alloc.rs:349)
by 0x62E0271: new<limbo_series::GenerateSeriesCursor> (boxed.rs:257)
by 0x62E0271: open_GenerateSeriesVTab (lib.rs:19)
by 0x425D8FA: limbo_core::VirtualTable::open (lib.rs:732)
by 0x4285DDA: limbo_core::vdbe::execute::op_vopen (execute.rs:890)
by 0x42351E8: limbo_core::vdbe::Program::step (mod.rs:396)
by 0x425C638: limbo_core::Statement::step (lib.rs:610)
by 0x40DB238: limbo::Statement::execute::{{closure}} (lib.rs:181)
by 0x40D9EAF: limbo::Connection::execute::{{closure}} (lib.rs:109)
by 0x40D54A1: example::main::{{closure}} (example.rs:26)
```
Interestingly, when using mimalloc, neither Valgrind nor mimalloc’s
internal statistics report the leak.
Reviewed-by: Preston Thorpe (@PThorpe92)
Closes#1447
This PR is an enabler for our (Coming Soon ™️ ) join reordering
optimizer -- simply adds the notion of a join order to the current query
execution. This PR does not do any join ordering -- the join order is
always the same as expressed in the SQL query.
Reviewed-by: Preston Thorpe (@PThorpe92)
Closes#1439
The following code reproduces the leak, with memory usage increasing
over time:
```
#[tokio::main]
async fn main() {
let db = Builder::new_local(":memory:").build().await.unwrap();
let conn = db.connect().unwrap();
conn.execute("SELECT load_extension('./target/debug/liblimbo_series');", ())
.await
.unwrap();
loop {
conn.execute("SELECT * FROM generate_series(1,10,2);", ())
.await
.unwrap();
}
}
```
After switching to the system allocator, the leak becomes detectable
with Valgrind:
```
32,000 bytes in 1,000 blocks are definitely lost in loss record 24 of 24
at 0x538580F: malloc (vg_replace_malloc.c:446)
by 0x62E15FA: alloc::alloc::alloc (alloc.rs:99)
by 0x62E172C: alloc::alloc::Global::alloc_impl (alloc.rs:192)
by 0x62E1530: allocate (alloc.rs:254)
by 0x62E1530: alloc::alloc::exchange_malloc (alloc.rs:349)
by 0x62E0271: new<limbo_series::GenerateSeriesCursor> (boxed.rs:257)
by 0x62E0271: open_GenerateSeriesVTab (lib.rs:19)
by 0x425D8FA: limbo_core::VirtualTable::open (lib.rs:732)
by 0x4285DDA: limbo_core::vdbe::execute::op_vopen (execute.rs:890)
by 0x42351E8: limbo_core::vdbe::Program::step (mod.rs:396)
by 0x425C638: limbo_core::Statement::step (lib.rs:610)
by 0x40DB238: limbo::Statement::execute::{{closure}} (lib.rs:181)
by 0x40D9EAF: limbo::Connection::execute::{{closure}} (lib.rs:109)
by 0x40D54A1: example::main::{{closure}} (example.rs:26)
```
Interestingly, when using mimalloc, neither Valgrind nor mimalloc’s
internal statistics report the leak.
This commit adds suport for DROP INDEX.
Bytecode produced by this commit differs from SQLITE's bytecode, main
reason we don't do autovacuum or repacking of pages like SQLITE does.
### The problem:
Sqlite displays the column names of the underlying vtab module when
displaying the `.schema`
Previously limbo omitted this, which makes it difficult for the user to
see what/how many columns the module's table has.
This matches sqlite's behavior by fetching the module's schema when the
schema entry is being inserted in translation.
Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>
Closes#1168
Closes#1413 . Basically, SQLite emits a check in a transaction to see
if it is attempting to write. If the db is in read only mode, it throws
an error, else the statement is executed. Mirroring how Rusqlite does
it, I modified the `OpenFlags` to use bitflags to better configure how
we open our VFS. This modification, will enable us to run tests against
the same database in parallel.
Closes#1433
closes #1417
Man chasing this down was much much harder than it should have been.
We very frequently call `read_page` then push the return value onto the
page stack, or otherwise use it without it necessarily needing to not be
'in progress' of IO, so it was tricky to figure out where this was
happening and it had me thinking that it was something wrong with the
changes to `io_uring` on my branch.
Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>
Closes#1418
we had an incorrect optimization in `eliminate_orderby_like_groupby()`
where it could remove e.g. the first term of the ORDER BY if it matched
the first GROUP BY term and the result set was naturally ordered by that
term. this is invalid. see e.g.:
```sql
main branch - BAD: removes the `ORDER BY id` term because the results are naturally ordered by id.
However, this results in sorting the entire thing by last name only!
limbo> select id, last_name, count(1) from users GROUP BY 1,2 order by id, last_name desc limit 3;
┌──────┬───────────┬───────────┐
│ id │ last_name │ count (1) │
├──────┼───────────┼───────────┤
│ 6235 │ Zuniga │ 1 │
├──────┼───────────┼───────────┤
│ 8043 │ Zuniga │ 1 │
├──────┼───────────┼───────────┤
│ 944 │ Zimmerman │ 1 │
└──────┴───────────┴───────────┘
after fix - GOOD:
limbo> select id, last_name, count(1) from users GROUP BY 1,2 order by id, last_name desc limit 3;
┌────┬───────────┬───────────┐
│ id │ last_name │ count (1) │
├────┼───────────┼───────────┤
│ 1 │ Foster │ 1 │
├────┼───────────┼───────────┤
│ 2 │ Salazar │ 1 │
├────┼───────────┼───────────┤
│ 3 │ Perry │ 1 │
└────┴───────────┴───────────┘
I also refactored sorters to always use the ast `SortOrder` instead of boolean vectors, and use the `compare_immutable()` utility we use inside btrees too.
Closes#1365
