What causes "Failed to load position events: {e}" in nautechsystems/nautilus_trader?

Inspect the wrapped sqlx error for the exact cause (relation missing, decode error, connection).

Failed to load position events: {e}

Error message

Failed to load position events: {e}

What it means

load_position_events runs a SELECT returning the fill events (JSON) for a position_id; when the query fails the sqlx error is wrapped in this message. The caller cannot replay the position because its events could not be read.

Source

Thrown at crates/infrastructure/src/sql/queries.rs:925

    ///
    /// Returns an error if the SQL SELECT or deserialization fails.
    pub async fn load_position_events(
        pool: &PgPool,
        position_id: &PositionId,
    ) -> anyhow::Result<Vec<OrderFilled>> {
        sqlx::query_as::<_, OrderFilledRow>(
            r#"
            SELECT *
            FROM "position_event"
            WHERE position_id = $1
            ORDER BY event_sequence ASC
        "#,
        )
        .bind(position_id.to_string())
        .fetch_all(pool)
        .await
        .map(|rows| rows.into_iter().map(|row| row.0).collect())
        .map_err(|e| anyhow::anyhow!("Failed to load position events: {e}"))
    }

    /// Loads and replays a complete `Position` for a `position_id` via the provided `pool`.
    ///
    /// # Errors
    ///
    /// Returns an error if loading events, loading instruments, or replaying fills fails.
    pub async fn load_position(
        pool: &PgPool,
        position_id: &PositionId,
    ) -> anyhow::Result<Option<Position>> {
        if let Some(snapshot) = Self::load_position_snapshot(pool, position_id).await?
            && let Some(replay_state) = snapshot.replay_state
        {
            return serde_json::from_value(replay_state)
                .map(Some)
                .map_err(|e| anyhow::anyhow!("Failed to decode position replay state: {e}"));
        }

View on GitHub (pinned to 18893faf8b)

Solutions

Inspect the wrapped sqlx error for the exact cause (relation missing, decode error, connection).
Apply the nautilus SQL migrations to create the position_event table.
Verify the database connection settings point at the intended schema/database.
If a row fails to decode as JSON, inspect and repair or remove the offending position_event row.

Defensive patterns

Strategy: retry

Validate before calling

sqlx::query("SELECT 1 FROM position_event LIMIT 1").fetch_optional(&pool).await?;

Try / catch

match load_position_events(&pool, &pid).await {
    Err(e) if is_transient_db_error(&e) => retry_with_backoff(3),
    other => other,
}

Prevention

Apply migrations before reading positions.
Validate JSONB integrity of position_event rows after manual data operations.
Point configuration at the correct database/schema.

When it happens

Trigger: Calling load_position_events(pool, position_id) where the fetch_all on the position events query errors: table missing, connection failure, or JSON column type mismatch.

Common situations: Schema not migrated; database unreachable; corrupted JSONB values causing decode errors during row fetch; wrong database pointed to by configuration.

Understand the failure class

Background: Database query failed: Internal Server Error 500s wrapping SQL, Prisma, and connection failures — what to check first — this error's family across 16 libraries.

Related errors

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/4cc403ecaae64e56. Report an issue: GitHub.