SPI_getvalue returns the string
representation of the value of the specified column.
The result is returned in memory allocated using
palloc. (You can use
pfree to release the memory when you don't need
input row to be examined
input row description
column number (count starts at 1)
Column value, or NULL if the column is null, colnumber is out of range (SPI_result is set to SPI_ERROR_NOATTRIBUTE), or no output function is available (SPI_result is set to SPI_ERROR_NOOUTFUNC).