From: | Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> |
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To: | Gabriel Furstenheim Milerud <furstenheim(at)gmail(dot)com> |
Cc: | pgsql-general(at)lists(dot)postgresql(dot)org |
Subject: | Re: Check that numeric is zero |
Date: | 2023-05-06 22:07:31 |
Message-ID: | 878re1b1i3.fsf@news-spur.riddles.org.uk |
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Thread: | |
Lists: | pgsql-general |
>>>>> "Gabriel" == Gabriel Furstenheim Milerud <furstenheim(at)gmail(dot)com> writes:
Gabriel> Hi,
Gabriel> I'm writing a Postgres native extension and I would like to
Gabriel> check that a numeric is zero.
Gabriel> My problem is that all exported methods like numeric_eq or
Gabriel> numeric_sign require me to have a numeric to start with, and
Gabriel> const_zero is not exported in numeric.c.
Currently the easiest and most portable way to get a numeric constant is
to call int4_numeric or int8_numeric via DirectFunctionCall; if you
don't care about versions older than pg14 there's also int64_to_numeric
which can be called directly from C.
Datum zero_num = DirectFunctionCall1(int4_numeric, Int32GetDatum(0));
(remember that this will be allocated in the current memory context; if
you want to keep a copy long-term, you'd want to datumCopy it somewhere
else.)
--
Andrew (irc:RhodiumToad)
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