Hi Toby,
On 12/14/2012 03:40 AM, Toby Murray wrote:
Sure but in this case I would suggest naming this option
differently because setting keepInvalidWays to false implies that
there will be no invalid ways in the database which may not be true
with the current implementation of this option.
Well technically there is a difference between way validity and
linestring validity :)
Yeah, I am/was using the term way/linestring interchangeably... In any
case my opinion is that naming this option keepInvalidWays is a bit of a
stretch since it can lead to dangerous assumptions like assuming that
all way geometry (linestrings) are valid which is not correct.
Yes, it would in theory be possible with the JTS library. Do you
have any idea how efficient this check is? If it takes 1 ms to check
for linestring validity then it will add 28 hours to a planet import
at which point it would be faster to do a "DELETE where not
ST_IsValid()" query after the data is loaded. But I guess I might
play around with it and see.
I have not used JTS directly so I am not sure about performance. My
guess from experience with PostGIS would be that it won't matter too
much since I have not encountered ST_IsValid/ST_MakeValid calls that
last longer than a few milliseconds. Validity code in JTS should be
pretty much the same in JTS as in GEOS/PostGIS but the only way to
really find out is to do a real benchmark...
The other problem is that this method can't be used in replication
mode since the linestring is built in SQL. But checking node count
still works.
During replication it would be possible to simply use ST_IsValid from
PostGIS but then the question is what to do with ways that become
invalid in some new replicated version - remove them altogether?
I still think the code I have right now is useful. The biggest plus
is that it creates consistency between what happens during import
and what happens during diff application. And it takes care of a
vast majority of the problem cases at the cost of (more or less) one
if statement.
Sure, I'm not saying it's not useful, I just have a small problem with
naming since invalid geometry gave me *a lot* of headaches one time and
I would prefer to have it very clearly documented.
Ultimately it is up to you and/or Brett as the maintainer to decide how
to name it, I can always add some note to wiki documentation about this
so all in all it's not a big deal.
Paweł
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