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4

Overlay operators like Contains, Intersection, SymDifference, etc. require exact noding. This is because there are floating point differences on the order of 1e-14 when interpolations are performed between two lines that are not equal. And while 1e-14 is a tiny number, it is still not zero. Use ST_Snap to help "snap" vertices from one geometry onto another ...


4

At the scale of your display, these lines appear to be coincident, but in reality they're not: I've exaggerated the difference between the two lines using the "Magnify Topology" tool in JTS TestBuilder, which I highly recommend for looking into cases like this. Depending on the goal of your analysis, it might be suitable to snap your vertices to a grid ...


2

Layers published as sql views are not editable, you have to publish them as normal tables instead


1

There are two views that you need to check geometry_columns and geography_columns that will provide you with a list like: "ian";"public";"coastline";"geom";2;27700;"MULTILINESTRING" "ian";"public";"motorway";"geom";2;27700;"MULTILINESTRING"


1

Updating is often quite slow. If it is possible, it is probably a lot faster to recreate the whole table like create table new_table as select pnt.*, poly.name from point_table pnt inner join poly_table poly on st_within(pnt.geom, poly.geom); I do this a lot and rename the new table to the original name and recreate indexes and constraints on it. If it ...


1

It looks like you have confused the username and the database name. If you created a database called shashi, you should have Database: shashi in the QGIS PostGIS Connection window. Your username is likely postgres. If that doesn't work, look in the message log. My logs are in /usr/local/pgsql/var/, but they may be somewhere else on your machine.



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