Tracing

Toasty emits structured events through the tracing crate. The most common reason to enable them is to see the SQL each query produces. Toasty does not print anything by default — install a subscriber in your application and the events appear.

Seeing executed SQL

The SQL drivers emit a tracing::debug! event for every statement they send to the database. Install tracing-subscriber with the env-filter feature and run with RUST_LOG=toasty=debug:

[dependencies]
tracing-subscriber = { version = "0.3", features = ["env-filter"] }

use tracing_subscriber::EnvFilter;

#[tokio::main]
async fn main() -> toasty::Result<()> {
    tracing_subscriber::fmt()
        .with_env_filter(EnvFilter::from_default_env())
        .init();

    let db = toasty::Db::builder()
        .models(toasty::models!(crate::*))
        .connect("sqlite::memory:")
        .await?;

    // ... queries here ...
    Ok(())
}

Run the program with:

RUST_LOG=toasty=debug cargo run

Each query produces two events. The engine logs the statement kind, and the driver logs the SQL it sends:

DEBUG toasty::engine: executing statement stmt.kind="query"
DEBUG toasty_driver_sqlite: executing SQL db.system="sqlite" db.statement=SELECT tbl_0_0."id", tbl_0_0."name" FROM "users" AS tbl_0_0 WHERE tbl_0_0."id" = ?1; params=1

The SQL event carries three fields:

db.statement is recorded with the Display representation, so the SQL appears bare in the default fmt subscriber — no surrounding quotes, no escaping of the identifier quotes inside.

Parameter values are passed to the driver as typed bindings and are not included in the trace. To inspect a specific parameter, log it from your application code.

The field names follow OpenTelemetry’s database semantic conventions, so subscribers that understand those conventions (for example, an OTLP exporter) pick the SQL up without extra mapping.

Filtering to one driver

RUST_LOG accepts per-target directives. To see SQL from one driver only, filter on its crate:

# Only PostgreSQL statements
RUST_LOG=toasty_driver_postgresql=debug cargo run

# Only SQLite statements
RUST_LOG=toasty_driver_sqlite=debug cargo run

# Only MySQL statements
RUST_LOG=toasty_driver_mysql=debug cargo run

Other events

The info level reports lifecycle events: schema build, database ready, and applied migrations. Enable it with RUST_LOG=toasty=info.

At debug, the engine also dumps the decoded result of each statement (Final result from var ...) alongside the SQL event. This is verbose on large result sets; filter it out with RUST_LOG=toasty=debug,toasty::engine::exec=info if you only want the SQL.

The trace level adds per-operation detail — driver dispatch, execution plan size, and transaction begin/commit/rollback. It is verbose; reach for it when debug does not show enough.

RUST_LOG=toasty=trace cargo run

DynamoDB

The DynamoDB driver does not run SQL, but it emits tracing::trace! events for each item operation it performs (getting single item, querying primary key, batch inserting items, and so on) with the table name, index name, and item counts. Enable them with RUST_LOG=toasty_driver_dynamodb=trace.