Provided by: postgresql-doc-10_10.23-0ubuntu0.18.04.2_all 

NAME
SPI_finish - disconnect a procedure from the SPI manager
SYNOPSIS
int SPI_finish(void)
DESCRIPTION
SPI_finish closes an existing connection to the SPI manager. You must call this function after completing the SPI operations needed during your procedure'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.
RETURN VALUE
SPI_OK_FINISH if properly disconnected SPI_ERROR_UNCONNECTED if called from an unconnected procedure