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Re: Weirdness in CHECK?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Christopher Kings-Lynne" <chriskl(at)familyhealth(dot)com(dot)au>
Cc: "Pgsql-Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Weirdness in CHECK?
Date: 2001-01-04 05:27:28
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Lists: pgsql-hackers
"Christopher Kings-Lynne" <chriskl(at)familyhealth(dot)com(dot)au> writes:
> Is this correct behaviour?  Perhaps it is, as CHECK is checking the
> truncated value - but I just want to make sure it's not a bug!

I think some people feel that we ought to raise an error rather than
silently truncating the input.  However, given that we do intend to
truncate the input, it seems to me that applying CHECK constraints
post-truncation is the Right Thing.  In general a CHECK ought to be
applied after any conversion ops needed to create a value of the
destination column type.  For example, if I had "CHECK (foo < 1)"
on a column foo declared NUMERIC(3,2), I'd be unhappy if the input
"0.999" got past the check because it was rounded to 1.00 only after
the CHECK was applied.

			regards, tom lane

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