# sqlite-ll
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Low-level interface to the [SQLite] database.
This is a rewrite of the [sqlite crate], and components used from there have
been copied under the MIT license.
<br>
## Why do we need another sqlite interface?
It is difficult to set up and use prepared statements with existing crates,
because they are all implemented in a manner which requires the caller to
borrow the connection in use.
Prepared statements can be expensive to create and *should* be cached and
re-used to achieve the best performance. Statements can also benefit from
using the [`Prepare::PERSISTENT`] option This library uses
`sqlite3_close_v2` when the connection is dropped, causing the closing of
the connection to be delayed until resources associated with it has been
closed.
We've also designed this library to avoid intermediary allocations. So for
example [calling `execute`] doesn't allocate externally of the sqlite3
bindings. This was achieved by porting the execute implementation from the
sqlite library and works because sqlite actually uses UTF-8 internally but
this is not exposed in the legacy C API that other crates use to execute
statements.
<br>
## Example
Open an in-memory connection, create a table, and insert some rows:
```rust
use sqlite_ll::Connection;
let c = Connection::open_memory()?;
c.execute(
r#"
CREATE TABLE users (name TEXT, age INTEGER);
INSERT INTO users VALUES ('Alice', 42);
INSERT INTO users VALUES ('Bob', 69);
"#,
)?;
```
Querying data using a parepared statement with bindings:
```rust
use sqlite_ll::State;
let mut stmt = c.prepare("SELECT * FROM users WHERE age > ?")?;
let mut results = Vec::new();
for age in [40, 50] {
stmt.reset()?;
stmt.bind(1, age)?;
while let State::Row = stmt.step()? {
results.push((stmt.read::<String>(0)?, stmt.read::<i64>(1)?));
}
}
let expected = vec![
(String::from("Alice"), 42),
(String::from("Bob"), 69),
(String::from("Bob"), 69),
];
assert_eq!(results, expected);
```
[`Prepare::PERSISTENT`]: https://docs.rs/sqlite-ll/latest/sqlite_ll/struct.Prepare.html#associatedconstant.PERSISTENT
[calling `execute`]: https://docs.rs/sqlite-ll/latest/sqlite_ll/struct.Connection.html#method.execute
[sqlite crate]: https://github.com/stainless-steel/sqlite
[SQLite]: https://www.sqlite.org