rltbl_db

rltbl_db is the database layer for rltbl. It provides an async abstraction over multiple database libraries, currently tokio-postgres and rusqlite. Our goal is to be able to switch databases at runtime, and query arbitrary tables using dynamically generated SQL.

Only consider using this library if all three are true:

1. you need to support multiple database types at runtime
2. you need to handle tables that you don't know the structure of at compile time
3. other options such as sqlx don't suit your needs.

Install

Add to your Cargo.toml using this GitHub repo:

cargo add rltbl_db --git 'https://github.com/rltbl/rltbl_db'

Usage

use rltbl_db::{any::AnyPool, core::{DbError, DbQuery}};

async fn example() -> Result<String, DbError> {
    let pool = AnyPool::connect("test.db").await?;
    pool.execute_batch(
        "DROP TABLE IF EXISTS test;\
         CREATE TABLE test ( value TEXT );\
         INSERT INTO test VALUES ('foo');",
    ).await?;
    let value = pool.query_string("SELECT value FROM test;", &[]).await?;
    Ok(value)
}

Differences between PostgreSQL and SQLite

The libsql and deadpool-sqlite drivers do not fully support querying special floating point types such as "NaN", "-Infinity", "Infinity", etc. If one tries to query from a column that contains such values the results will be returned as TEXT. It is, possible, however, to insert these special values into a table by hard coding them into the submitted query text (rather than by using dynammic query parameters), by double quoting them. E.g., INSERT INTO foo VALUES ("NaN").

There are no such issues with PostgreSQL. The following will work irrespective of whether the column bar is of floating point or text type (postgresql will be able to determine this implicitly): INSERT INTO foo (bar) VALUES ('-Infinity'). Note that one must use single- rather than double-quotes for postgresql. It is also possible to use these special values as parameters, e.g.,

        let float_param = std::f64::from_str("-Infinity").unwrap();
        pool.execute(
            r#"INSERT INTO foo (bar) VALUES ($1)"#,
            params![float_param],
        )
        .await
        .unwrap();