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<div>I'm working on the regression-tests for the distance-functions and don't really understand the behavior of postgis or the planner or what it is, doing it.</div>
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<div>if I run:<br />
select st_astext(geom1) from<br />
(select NULL as geom1) a;</div>
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<div>I get:</div>
<div><br />
FEIL: failed to find conversion function from unknown to geometry</div>
<div><br />
********** Error **********</div>
<div>FEIL: failed to find conversion function from unknown to geometry<br />
SQL state: XX000</div>
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<div>but if I run:</div>
<div>select st_astext(NULL)</div>
<div>or</div>
<div>select st_astext(NULL) from<br />
(select NULL as geom1) a;</div>
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<div>then I just get an empty answer without error-message.</div>
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<div>and if I run :</div>
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<div>select geom1 from<br />
(select NULL as geom1) a;</div>
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<div>I also get just an empty answer.</div>
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<div>Why is this conversion-function trigged when I use a sub-query and not otherwise and only if I use the NULL-value in a function and not if I just show it.</div>
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