SPI_rollback, SPI_rollback_and_chain — abort the current transaction
void SPI_rollback(void)
void SPI_rollback_and_chain(void)
   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 SPI_connect_ext.