SPI_rollback, SPI_rollback_and_chain — abort the current transaction
SPI_rollback rolls back the current transaction. It is approximately equivalent to running the SQL command
ROLLBACK. After a transaction is rolled back, a new transaction has to be started using
SPI_start_transaction before further database actions can be executed.
SPI_rollback_and_chain is the same, but a new transaction is immediately started with the same transaction characteristics as the just finished one, like with the SQL command
ROLLBACK AND CHAIN.
These functions can only be executed if the SPI connection has been set as nonatomic in the call to