Due to asynchronous nature of the library, there are few places where an exception can be thrown. Most of error are passed to callbacks.

Places where an exception can be thrown:

tip::db::pg::db_service::add_connection - tip::db::pg::error::connection_error, when the connection string is invalid or lacks some information
tip::db::pg::db_service::begin - tip::db::pg::error::connection_error, when the database alias is not configured.
when trying to extract a value from a null field - tip::db::pg::error::value_is_null

The rest of errors are passed via callbacks. If an error occurs inside a transaction, it is rolled back. If the error is an error sent by the server, it is passed to the query error callback. If an exception is thrown by any callback, it is passed to the transaction error callback. If the transaction error callback throws an error, it is silently caught and suppressed.