detecting NULL column in SPI function

Hello,

In a SPI function I have this code snippet:

double startprice = *DatumGetFloat64(SPI_getbinval(
auction_tt->vals[i], auction_tt->tupdesc,
SPI_fnumber(auction_tt->tupdesc, "startprice"), &isnull));

To extract a value from the startprice column. It only works if
"startprice" is not NULL, otherwise the backend crashes.

In the provided example SPI functions I couldn't determine a good way of
testing for NULL on columns. Should I first try to return the Datum,
test it for NULL, then run DatumGetFloat64() on it? Isn't there a
simpler way?

Thanks in advance for your help, cheers,

--
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A singular instrument worn at the end of a human arm and
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