Re: floating point output - Mailing list pgsql-general

> On Sep 5, 2019, at 7:32 AM, Rob Sargent <robjsargent@gmail.com> wrote:
>
>
>
>> On Sep 4, 2019, at 9:14 PM, Adrian Klaver <adrian.klaver@aklaver.com> wrote:
>>
>>> On 9/4/19 5:23 PM, Rob Sargent wrote:
>>> I've found the description of floating point types (here
<https://www.postgresql.org/docs/10/datatype-numeric.html#DATATYPE-FLOAT>),but I'm looking for the rationale of the
outputformat, particularly with respect to total digits presented (variable in a single select's output) and the
droppingof a trailing zero (to some implying a loss of precision).  Is the code my only guide here? 
>>
>> Some examples would help explain your concerns.
>>
>> Bottom line, if you want precision use numeric.
>>
>>
>>
> When at my desk I’ll give example. Actual precision is not the issue. Purely cosmetics.

Below I show a floating point column from a recent query.

Here's my guess at what's happening in the formatting:
  1) scientific notation if smaller than 1.0e-04 (I’m not in the very-much-larger-than-one world)
  2) 15 digits after the most signicant 0
  3) remove trailing zeros

I may be alone in this but I find the presentation messy and that's unusual in the PostgreSQL world.  To me the most
agregiousis the truncation of the zeros.  Pick a number of digits and stick with it. One format too. 

    1 |  8.8999911000089e-05 |
    2 |  0.00010999989000011 |
    3 |  0.00011999988000012 |
    4 | 0.000128999871000129 |
    5 | 0.000132499966875008 |
    6 | 0.000132999867000133 |
    7 | 0.000136922971597714 |
    8 | 0.000139499930250035 |
    9 | 0.000158809516247166 |
   10 | 0.000170294107629758 |
   11 |  0.00028999971000029 |
   12 | 0.000327999672000328 |
   13 | 0.000628999371000629 |
   14 |  0.00065999934000066 |
   15 | 0.000667999332000668 |
   16 | 0.000681999318000682 |
   17 | 0.000683999316000684 |
   18 | 0.000708999291000709 |
   19 | 0.000722999277000723 |
   20 | 0.000730999269000731 |
   21 |  0.00074999925000075 |
   22 | 0.000753999246000754 |
   23 | 0.000755999244000756 |
   24 | 0.000762999237000763 |
   25 | 0.000765999234000766 |
   26 | 0.000773999226000774 |
   27 | 0.000780999219000781 |
   28 | 0.000785999214000786 |
   29 | 0.000787999212000788 |
   30 | 0.000791999208000792 |
   31 | 0.000793999206000794 |
   32 | 0.000813999186000814 |
   33 | 0.000817999182000818 |
   34 | 0.000826999173000827 |
   35 | 0.000833999166000834 |
   36 | 0.000834999165000835 |
   37 | 0.000838999161000839 |
   38 | 0.000847999152000848 |
   39 | 0.000854999145000855 |
   40 | 0.000855999144000856 |
   41 | 0.000857999142000858 |
   42 |  0.00085999914000086 |
   43 | 0.000864999135000865 |
   44 |  0.00086999913000087 |
   45 | 0.000875999124000876 |
   46 | 0.000882999117000883 |
   47 | 0.000887999112000888 |
   48 | 0.000887999112000888 |
   49 | 0.000904999095000905 |
   50 | 0.000910999089000911 |
   51 | 0.000912999087000913 |
   52 | 0.000912999087000913 |
   53 | 0.000914999085000915 |
   54 | 0.000921999078000922 |
   55 | 0.000922999077000923 |
   56 | 0.000938999061000939 |
   57 |  0.00094999905000095 |
   58 | 0.000967999032000968 |
   59 | 0.000971999028000972 |
   60 | 0.000982999017000983 |
   61 | 0.000995999004000996 |
   62 |    0.001000998999001 |
   63 |    0.001003998996001 |
   64 |    0.001003998996001 |
   65 |  0.00101099898900101 |
   66 |  0.00101199898800101 |
   67 |  0.00101599898400102 |
   68 |  0.00101899898100102 |
   69 |  0.00102199897800102 |
   70 |  0.00102599897400103 |
   71 |  0.00103099896900103 |
   72 |  0.00104999895000105 |
   73 |  0.00106899893100107 |
   74 |  0.00107499892500108 |
   75 |  0.00107599892400108 |
   76 |  0.00108499891500109 |
   77 |  0.00108699891300109 |
   78 |  0.00108799891200109 |
   79 |   0.0011039988960011 |
   80 |  0.00110799889200111 |
   81 |  0.00111099888900111 |
   82 |  0.00111299888700111 |
   83 |  0.00111599888400112 |
   84 |  0.00111699888300112 |
   85 |  0.00111999888000112 |
   86 |  0.00111999888000112 |
   87 |  0.00112099887900112 |
   88 |  0.00116599883400117 |
   89 |  0.00117461448106578 |
   90 |   0.0011788180746529 |
   91 |  0.00118099881900118 |
   92 |   0.0011839994080003 |
   93 |  0.00118827261924794 |
   94 |  0.00118899881100119 |
   95 |   0.0012049987950012 |
   96 |  0.00120622217754733 |
   97 |  0.00120999879000121 |
   98 |  0.00121409079871902 |
   99 |  0.00121481807138018 |
  100 |  0.00122618178102479 |
  101 |  0.00122699877300123 |
  102 |  0.00122899877100123 |
  103 |  0.00123999876000124 |
  104 |  0.00125999874000126 |
  105 |  0.00127766866245761 |
  106 |  0.00128099935950032 |
  107 |  0.00129099870900129 |
  108 |  0.00129199870800129 |
  109 |  0.00129299870700129 |
  110 |  0.00129924967518758 |
  111 |   0.0013019986980013 |
  112 |   0.0013019986980013 |
  113 |  0.00130449934775033 |
  114 |  0.00133099866900133 |
  115 |  0.00133106666886731 |
  116 |  0.00135249932375034 |
  117 |  0.00137999988500001 |
  118 |  0.00142799857200143 |
  119 |  0.00143799856200144 |
  120 |  0.00144399855600144 |
  121 |   0.0014563623123979 |
  122 |  0.00146199853800146 |
  123 |  0.00148299851700148 |
  124 |   0.0014969985030015 |
  125 |  0.00151499848500151 |
  126 |  0.00151599848400152 |
  127 |  0.00154699845300155 |
  128 |  0.00154809076835538 |
  129 |  0.00156599843400157 |
  130 |  0.00156999843000157 |
  131 |  0.00157899842100158 |
  132 |  0.00163499836500163 |
  133 |  0.00165199834800165 |
  134 |  0.00165299917350041 |
  135 |  0.00167799832200168 |
  136 |  0.00168699831300169 |
  137 |  0.00171599914200043 |
  138 |  0.00172849913575043 |
  139 |  0.00174599825400175 |
  140 |  0.00199399800600199 |
  141 |   0.0028989971010029 |
  142 |  0.00417999582000418 |
  143 |  0.00436199563800436 |