[postgis-users] St_makevalid issue

[Paul van der Linden]

I have a query that gives inconsistent results.
It almost seems like st_makevalid doesn't always produce the same results
given the same input, and sometimes even returns invalid geometries...

Results are
f;1159320407;"Bangladesh"
f;1159321073;"Mozambique"
f;1159316737;"Nord"
f;1159314827;"Uusimaa"

second run:
f;1159321073;"Mozambique"
t;1159315455;"Syddanmark"
t;1159314827;"Uusimaa"
t;1159317795;"Gerona"

third run:
f;1159321073;"Mozambique"
t;1159315455;"Syddanmark"

note the 't' in the second and third run...

Query:

SELECT ST_isvalid(simplifiedgeo2),* FROM (
SELECT
    foo2.ne_id,
    foo2.name,
    CASE
        WHEN ST_isvalid(foo2.simplifiedgeo) THEN foo2.simplifiedgeo
        ELSE ST_makevalid(foo2.simplifiedgeo)
    END AS simplifiedgeo2
   FROM (
     SELECT
       ST_simplifypreservetopology(foo.geom,
         LEAST(
           ST_xmax(foo.shiftedgeo::box3d) - ST_xmin(foo.shiftedgeo::box3d),
ST_ymax(foo.shiftedgeo::box3d) - ST_ymin(foo.shiftedgeo::box3d))
         ) AS simplifiedgeo,
       foo.ne_id,
       foo.name,
       foo.geom
     FROM (
        SELECT
          natearth.ne_id,
          natearth.geom,
          natearth.name,
          CASE
              WHEN (
                ST_xmax(ST_shiftlongitude(natearth.geom)::box3d) -
ST_xmin(ST_shiftlongitude(natearth.geom)::box3d))
                <
                (ST_xmax(natearth.geom::box3d) -
ST_xmin(natearth.geom::box3d)
              ) THEN ST_shiftlongitude(natearth.geom)
              ELSE natearth.geom
          END AS shiftedgeo
          FROM (
             SELECT
                ne_10m_admin_0_countries_lakes.ne_id,
                ne_10m_admin_0_countries_lakes.geom,
                ne_10m_admin_0_countries_lakes.name
              FROM natural_earth.ne_10m_admin_0_countries_lakes
          UNION ALL
             SELECT
                ne_10m_admin_1_states_provinces_lakes.ne_id,
                ne_10m_admin_1_states_provinces_lakes.geom,
                ne_10m_admin_1_states_provinces_lakes.name
             FROM natural_earth.ne_10m_admin_1_states_provinces_lakes
          ) natearth
     ) foo
   ) foo2
) as fff
WHERE NOT ST_isvalid(simplifiedgeo2)

Any advice on how to further debug this?

"POSTGIS="2.5.1 r17027" [EXTENSION] PGSQL="110" GEOS="3.7.0-CAPI-1.11.0
3.7.1" PROJ="Rel. 4.9.3, 15 August 2016" GDAL="GDAL 2.2.4, released
2018/03/19 GDAL_DATA not found" LIBXML="2.7.8" LIBJSON="0.12"
LIBPROTOBUF="1.2.1" (core procs from "2.5.0 r16836" nee (...)"
"PostgreSQL 11.2, compiled by Visual C++ build 1914, 64-bit"

Running on windows 64-bit.
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