SPI_execp is the same as SPI_execute_plan, with the latter's read_only parameter always taken as false.
execution plan (returned by SPI_prepare)
An array of actual parameter values. Must have same length as the plan's number of arguments.
An array describing which parameters are null. Must have same length as the plan's number of arguments. n indicates a null value (entry in values will be ignored); a space indicates a nonnull value (entry in values is valid).
If nulls is NULL then SPI_execp assumes that no parameters are null.
maximum number of rows to process or return
See SPI_execute_plan.
SPI_processed and SPI_tuptable are set as in SPI_execute if successful.
