Recursive merging of overlapping arrays in a column

Hey mailing list,

i have the following Table:

I want to merge the arrays which have overlapping elements, so that I get
the result which doesn't contain overlapping arrays anymore:

I am not an expert in SQL and it took me a long time to come up with this
solution:

Which gives me the result:

Result number 3 is contained in number one and shouldn't be in the output
anymore, because I only want non overlapping arrays in the result.

Another problem I encountered is that the performance of this query seems to
be very bad. I tried running it on a larger table (~400000 arrays) and it is
still running after ~10h.

I would appreciate any input on this problems, so it would be nice if anyone
could give me a hint how to get only the merged arrays without overlaps in
the resultset and maybe how to build a more elegant and efficient query.

Thanks in advance,

Dave

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