read

read#

Read a single record by primary key or lookup criteria.

Rust API#

// sync_api
pub fn mudu_get(session_id: OID, key: &[u8]) -> RS<Option<Vec<u8>>> {
    /* ... */
}

// async_api
pub async fn mudu_get(session_id: OID, key: &[u8]) -> RS<Option<Vec<u8>>> {
    /* ... */
}

Conceptual signature#

read(table: string, key: KeyExpr, options?: { projection?: [string], for_update?: bool }) -> Row | null

Parameters#

  • table — target table or logical collection name.

  • key — primary key value or a structured key expression for lookup.

  • options.projection — optional list of column names to return.

  • options.for_update — when true, the read acquires locks to allow safe subsequent updates within the same transaction.

Behavior#

  • Performs a point lookup in the table or index and returns the matching row, or null if not found.

  • Reads respect the current transaction isolation and visibility rules (may return committed snapshot values depending on isolation).

Return value#

  • A single Row object with column values, or null when no row matches.

Errors#

  • NotFound is not an error; read returns null when no match.

  • LockConflict — when for_update is requested and lock acquisition fails.

Transaction semantics#

  • Reads inside an open transaction are subject to that transaction’s snapshot/isolation.

  • Reads outside a transaction follow host default semantics.

Example#

let row = mudu_get(oid, b"accounts:42")?;
if let Some(bytes) = row {
    // decode bytes according to the table schema
}

Notes#

  • Use projection to reduce data transferred and improve performance.

  • For read-modify-write patterns, prefer for_update to avoid lost-update races.