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0b0885325c
In sqlite3 generating the loop to read multiple joined tables follows
the pattern:
```c
sqlite3WhereBegin();
sqlite3WhereEnd();
```
and this generates:
```
sqlite> explain select * from users, products;
addr opcode p1 p2 p3 p4 p5 comment
---- ------------- ---- ---- ---- ------------- -- -------------
0 Init 0 23 0 0 Start at 23
1 OpenRead 0 2 0 10 0 root=2 iDb=0; users
2 OpenRead 1 3 0 3 0 root=3 iDb=0; products
3 Rewind 0 22 0 0
4 Rewind 1 22 0 0
5 Rowid 0 1 0 0 r[1]=users.rowid
6 Column 0 1 2 0 r[2]= cursor 0 column 1
7 Column 0 2 3 0 r[3]= cursor 0 column 2
8 Column 0 3 4 0 r[4]= cursor 0 column 3
9 Column 0 4 5 0 r[5]= cursor 0 column 4
10 Column 0 5 6 0 r[6]= cursor 0 column 5
11 Column 0 6 7 0 r[7]= cursor 0 column 6
12 Column 0 7 8 0 r[8]= cursor 0 column 7
13 Column 0 8 9 0 r[9]= cursor 0 column 8
14 Column 0 9 10 0 r[10]= cursor 0 column 9
15 Rowid 1 11 0 0 r[11]=products.rowid
16 Column 1 1 12 0 r[12]= cursor 1 column 1
17 Column 1 2 13 0 r[13]= cursor 1 column 2
18 RealAffinity 13 0 0 0
19 ResultRow 1 13 0 0 output=r[1..13]
20 Next 1 5 0 1
21 Next 0 4 0 1
22 Halt 0 0 0 0
23 Transaction 0 0 2 0 1 usesStmtJournal=0
24 Goto 0 1 0 0
```
`sqlite3WhereBegin()` as the name represents, mainly does stuff with
`WHERE` expressions + loop generation. This is why I decided to change
the name to `translate_tables_begin` to try improve the naming.
In our case:
```rust
translate_table_open_cursor(program, &mut context, select.from.as_ref().unwrap());
translate_table_open_loop(program, &mut context, loop_index);
```
translates into:
```sql
> explain select * from users, products;
addr opcode p1 p2 p3 p4 p5 comment
---- ------------- ---- ---- ---- ------------- -- -------
0 Init 0 28 0 0 Start at 28
1 OpenReadAsync 0 2 0 0 root=2
2 OpenReadAwait 0 0 0 0
3 OpenReadAsync 1 3 0 0 root=3
4 OpenReadAwait 0 0 0 0
5 RewindAsync 0 0 0 0
6 RewindAwait 0 27 0 0
7 RewindAsync 1 0 0 0
8 RewindAwait 1 25 0 0
9 RowId 0 0 0 0
10 Column 0 1 1 0 r[1]= cursor 0 column 1
11 Column 0 2 2 0 r[2]= cursor 0 column 2
12 Column 0 3 3 0 r[3]= cursor 0 column 3
13 Column 0 4 4 0 r[4]= cursor 0 column 4
14 Column 0 5 5 0 r[5]= cursor 0 column 5
15 Column 0 6 6 0 r[6]= cursor 0 column 6
16 Column 0 7 7 0 r[7]= cursor 0 column 7
17 Column 0 8 8 0 r[8]= cursor 0 column 8
18 Column 0 9 9 0 r[9]= cursor 0 column 9
19 RowId 1 10 0 0
20 Column 1 1 11 0 r[11]= cursor 1 column 1
21 Column 1 2 12 0 r[12]= cursor 1 column 2
22 ResultRow 0 13 0 0 output=r[0..13]
23 NextAsync 1 0 0 0
24 NextAwait 1 8 0 0
25 NextAsync 0 0 0 0
26 NextAwait 0 6 0 0
27 Halt 0 0 0 0
28 Transaction 0 0 0 0
29 Goto 0 1 0 0
```
This works on as many joined tables but... it is ready to extend for
further join operations.
Signed-off-by: Pere Diaz Bou <pere-altea@hotmail.com>
Limbo
Limbo is a work-in-progress, in-process OLTP database management system, compatible with SQLite.
Features
- In-process OLTP database engine library
- Asynchronous I/O support with
io_uring - SQLite compatibility
- SQL dialect support (wip)
- File format support (read-only)
- SQLite C API (wip)
- JavaScript/WebAssembly bindings (wip)
Getting Started
Limbo is currently read-only. You can either use the sqlite3 program to create a database:
$ sqlite3 database.db
SQLite version 3.42.0 2023-05-16 12:36:15
Enter ".help" for usage hints.
sqlite> CREATE TABLE users (id INT PRIMARY KEY, username TEXT);
sqlite> INSERT INTO users VALUES (1, 'alice');
sqlite> INSERT INTO users VALUES (2, 'bob');
or use the testing script to generate one for you:
./testing/gen-database.py
You can then start the Limbo shell with:
$ cargo run database.db
Welcome to Limbo SQL shell!
> SELECT * FROM users LIMIT 1;
|1|Cody|Miller|mhurst@example.org|525.595.7319x21268|33667 Shaw Extension Suite 104|West Robert|VA|45161|`
Developing
Run tests:
cargo test
Test coverage report:
cargo tarpaulin -o html
Run benchmarks:
cargo bench
Run benchmarks and generate flamegraphs:
echo -1 | sudo tee /proc/sys/kernel/perf_event_paranoid
cargo bench --bench benchmark -- --profile-time=5
Publications
- Pekka Enberg, Sasu Tarkoma, Jon Crowcroft Ashwin Rao (2024). Serverless Runtime / Database Co-Design With Asynchronous I/O. In EdgeSys ‘24. [PDF]
- Pekka Enberg, Sasu Tarkoma, and Ashwin Rao (2023). Towards Database and Serverless Runtime Co-Design. In CoNEXT-SW ’23. [PDF] [Slides]
License
This project is licensed under the MIT license.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Limbo by you, shall be licensed as MIT, without any additional terms or conditions.