Struct ExtensionTransaction 

pub struct ExtensionTransaction<'conn> { /* private fields */ }

A restricted statement executor for writing to application-owned extension tables within a wallet database transaction.

A handle of this type is provided by WalletDb::transactionally_with_extension alongside the wallet handle, and shares the same database transaction: statements run through it either commit atomically with the wallet operations performed in the same closure, or are rolled back together with them.

Authorization policy

Every statement executed through this type runs under a SQLite authorizer that is installed only for the duration of that single statement. The authorizer:

• allows reads (SELECT, and reads of individual rows and columns) against any table, so that extension statements may reference wallet data (for example, to satisfy a foreign key into an account row);
• allows INSERT, UPDATE, and DELETE only against tables whose names begin with the ext_ prefix reserved for external migrations (see WalletMigrator::with_external_migrations); and
• denies everything else, including all schema changes (DDL), PRAGMA, ATTACH/DETACH, and transaction-control actions (BEGIN, COMMIT, ROLLBACK, SAVEPOINT, RELEASE), so that extension statements cannot alter the wallet schema or interfere with the enclosing transaction.

Because writes are restricted to the ext_ prefix, a statement that inserts into an AUTOINCREMENT extension table is denied: SQLite services AUTOINCREMENT by writing to the internal sqlite_sequence table, which does not carry the prefix. Extension tables that must be written through this API should therefore avoid AUTOINCREMENT (an ordinary INTEGER PRIMARY KEY rowid, or an explicitly supplied key, works without it).

Implementations

impl<'conn> ExtensionTransaction<'conn>

pub fn execute(&self, sql: &str, params: impl Params) -> Result<usize, Error>

Executes a single non-query SQL statement against an extension table, returning the number of rows that were changed.

The statement is subject to the authorization policy documented on ExtensionTransaction; a statement that touches wallet-owned schema, or that attempts a denied action, fails with an authorization error and makes no changes.

pub fn query_row<T, F>( &self, sql: &str, params: impl Params, f: F, ) -> Result<T, Error>

where F: FnOnce(&Row<'_>) -> Result<T, Error>,

Executes a SQL query that is expected to return a single row, and applies f to that row to produce a result.

The statement is subject to the authorization policy documented on ExtensionTransaction. As with rusqlite::Connection::query_row, this returns rusqlite::Error::QueryReturnedNoRows if the query selects no rows.