Thanks to Peter for indexing "name" and "ref" in all 3 tables.
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I decided to use the columns(common keys) only if the column exist and if there is no
search for a special value in it
else I use the hstore.
It seem that the optimal solution is also dependent from the zoom-level, so on higher
zoomlevels an index is not so important.
We should find a way to test/optimize map styles more or less automatically or define the
right rules.
Greetings Kolossos