[mkgmap-dev] duplicate evaluation of tags

Mon May 5 06:11:05 BST 2014

Hi all,

there is still potential for optimisation:

To be able to create an index which gives
all rules for a tag like surface=gravel,
we order the expressions in the rules so
that they start with a tagkey=* or 
tagkey=value. 
We use the existing tags of an element 
to find the rules that have to be checked.
Now, if we find two rule like 

surface=gravel | surface=cobblestone {...}
surface=* & surface ~'(abc|xyz)' {...}

after searching for rules with tagkey surface=gravel
we should save the info that the 1st term in the 
expression is true.

However, there is more to it:
Other rules may delete or chang the tag surface=gravel,
so this may require too much logic.
Maybe it can be done with the new cacheId.

Gerd

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