[postgis-users] St_makevalid issue

Martin Davis mtnclimb at gmail.com
Thu Mar 26 11:36:33 PDT 2020

> >You could capture the full output from a few runs and provide that (with
> >geometry as WKB). That might allow seeing if the discrepancy is real and
> >why it is happening.

In the sample output you provided, the geometry for Barisal is indeed
invalid, but the isValid in the select list shows true.

For the record, I tried the query on PostGIS 3/GEOS 3.8, and it worked as
expected - no rows returned.

If this is truly a Heisenbug [1], it's going to be very hard to debug, and
even if tracked down, there's unlikely to be a simple fix.  The advice is
almost always to upgrade, since upgrades contain numerous fixes (and in
this case seem to definitely solve the problem).

If it's impossible to upgrade, you'll have to figure out a workaround.
Without knowing the use case it's impossible to recommend something.  I do
note that you are pushing the limits of ST_SimplifyPreserveTopology, which
seems like an odd thing to do.
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