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Re: need higher extra_float_digits value (3)

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Keh-Cheng Chu <kehcheng(at)solar2(dot)stanford(dot)edu>, pgsql-bugs(at)postgresql(dot)org
Subject: Re: need higher extra_float_digits value (3)
Date: 2009-09-10 01:18:50
Message-ID: 603c8f070909091818n2bf92d75j6d41d3e1c313c245@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-bugs
On Wed, Sep 9, 2009 at 6:04 PM, Tom Lane<tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Keh-Cheng Chu <kehcheng(at)solar2(dot)Stanford(dot)EDU> writes:
>> While 17 decimal digits are sufficient to guarantee the
>> complete recovery of all 64-bit double values, some 32-bit
>> reals actually require NINE significant figures.
>
> Hm, annoying.  Seems like we could do one of two things:
>
> 1. Increase the max extra_float_digits value to 3 and have pg_dump use
> that.
>
> 2. Split extra_float_digits into two settings so that float4 and float8
> can use different settings.
>
> Offhand the only argument I can see for #2 is that #1 might bloat dump
> files unnecessarily --- but it's not likely to be significant on a
> percentage basis.
>
> We'd also need to check the code to be sure it's leaving room for the
> extra digit in all cases, though I doubt there's really any problem.

(2) seems like overkill to me, FWIW.

...Robert

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