[postgis-users] Different hex POINT representation but the same coordinates?

[Darafei "Komяpa" Praliaskouski]

It's easy to see the difference if you ask for more precision:

18:26:40 [gis] > SELECT
ST_AsText(ST_GeomFromWKB('\x01010000000ad7a3f0735727c13d0ad7a3ae0c30c1'),150);

┌───────────────────────────────────────────────────────────────────────────────────────────┐

│                                         st_astext
                                        │
├───────────────────────────────────────────────────────────────────────────────────────────┤

│ POINT(-764857.96999999997206032276153564453125
-1051822.63999999989755451679229736328125) │
└───────────────────────────────────────────────────────────────────────────────────────────┘

(1 row)

Time: 24,109 ms
18:26:41 [gis] > SELECT
ST_AsText(ST_GeomFromWKB('\x01010000000ad7a3f0735727c13e0ad7a3ae0c30c1'),150);

┌──────────────────────────────────────────────────────────────────────────────────────────┐

│                                        st_astext
                                        │
├──────────────────────────────────────────────────────────────────────────────────────────┤

│ POINT(-764857.96999999997206032276153564453125
-1051822.6400000001303851604461669921875) │
└──────────────────────────────────────────────────────────────────────────────────────────┘

(1 row)

Time: 0,519 ms


On Mon, Oct 5, 2020 at 6:21 PM Michal Seidl <michal.seidl at gmail.com> wrote:

> Hello I have two points with different HEX representation but the same
> WKT representation? I do not know the binary representation in detail.
>
> The difference in HEX is somewhere in th middle "d" versus "e" value
>
> SELECT
> ST_AsEWKT(ST_GeomFromWKB('\x01010000000ad7a3f0735727c13e0ad7a3ae0c30c1'));
>
> SELECT
> ST_AsEWKT(ST_GeomFromWKB('\x01010000000ad7a3f0735727c13d0ad7a3ae0c30c1'));
>
> SELECT ST_GeomFromWKB('\x01010000000ad7a3f0735727c13e0ad7a3ae0c30c1') =
> ST_GeomFromWKB('\x01010000000ad7a3f0735727c13d0ad7a3ae0c30c1');
>
> So what is different?
>
> Michal
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