gistfile1.txt

[package]
name = "app"
version = "0.1.0"
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
env_logger = "0.6.0"
serde = { version = "1.0", features = ["derive"] }
serde_json = "1"
serde_rusqlite = "0.29.0"
rusqlite = "0.26.3"

gistfile2.txt

root@143389edf290:/app# rm ruru.db && cargo run
   Compiling app v0.1.0 (/app)
    Finished dev [unoptimized + debuginfo] target(s) in 0.47s
     Running `target/debug/app`
Err(Deserialization("invalid type: string \"{\\\"key\\\": \\\"value\\\"}\", expected a map"))

main.rs

use rusqlite::{params, Connection, Result};
use serde_rusqlite::from_rows_ref;
use serde::Serialize;
use serde::Deserialize;
use rusqlite::named_params;
use std::collections::HashMap;

#[derive(Serialize, Deserialize, Debug, Clone)]
struct User {
    id: i32,
    username: String,
    labels: HashMap<String, String>
}

fn main() {
    let connection = Connection::open("ruru.db").unwrap();

    connection.execute("CREATE TABLE user (
        id              INTEGER PRIMARY KEY,
        username        TEXT NOT NULL,
        labels          JSON NOT NULL
    )", params![]).unwrap();

    connection.execute("INSERT INTO user (username, labels) VALUES (:username, :labels)",
        named_params!{
            ":username": "John Doe",
            ":labels": "{\"key\": \"value\"}"
        }
    ).unwrap();

    let mut statement = connection.prepare("SELECT * FROM user LIMIT 1").unwrap();
    let mut rows = statement.query([]).unwrap();
    let mut ref_rows = from_rows_ref::<User>(&mut rows);
    let result = ref_rows.next();

    let user = result.unwrap();

    println!("{:?}", user);
}