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Re: Odd numeric->float4/8 casting behaviour

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Gregory Stark <stark(at)enterprisedb(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Odd numeric->float4/8 casting behaviour
Date: 2007-01-04 16:21:17
Message-ID: 17690.1167927677@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Gregory Stark <stark(at)enterprisedb(dot)com> writes:
> I believe this is happening because the numeric is being cast to float8 and
> then the float4-float8 cross-data-type operator is being used. It seems like
> it would be preferable to cast it to float4 and use the non-cross-data-type
> operator. They're both marked as implicit casts so I'm unclear what decides
> which gets used.

Without having traced through the code, I think the fact that float8 is
a "preferred type" is driving it.  It's not clear whether we could
change this without getting into a "can't resolve ambiguous operator"
problem.

> Also, as a side note I was surprised to find the above being parsed as
> -(0.999::numeric(3,3)) rather than (-0.999)::numeric(3,3) is that expected?

Yeah, :: binds VERY tightly.

			regards, tom lane

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Subject: Re: Odd numeric->float4/8 casting behaviour
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