SPI_prepare's parameter

[高健 <luckyjackgao@xxxxxxxxx>]

I am new to PostgreSQL's SPI(Server Programming Interface).

I can understand PostgreSQL's exampel of using SPI. But I am not sure about SPI_prepare's parameter.

void * SPI_prepare(const char * command, int nargs, Oid * argtypes)

Can somebody kindly give an example of using SPI_prepare ?