Re: floating point output

> On Sep 5, 2019, at 7:32 AM, Rob Sargent <robjsargent(at)gmail(dot)com> wrote:
>
>
>
>> On Sep 4, 2019, at 9:14 PM, Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)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 output format, particularly with respect to total digits presented (variable in a single select's output) and the dropping of 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 agregious is 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 |