SPI_finish — disconnect a C function from the SPI manager
int SPI_finish(void)
   SPI_finish closes an existing connection to
   the SPI manager.  You must call this function after completing the
   SPI operations needed during your C function's current invocation.
   You do not need to worry about making this happen, however, if you
   abort the transaction via elog(ERROR).  In that
   case SPI will clean itself up automatically.
  
SPI_OK_FINISHif properly disconnected
SPI_ERROR_UNCONNECTEDif called from an unconnected C function