Intersection Tool Produces two Intersection points on the same position when performed on Same Layer

[qgib]

Author Name: Sibi Prabakaran (Sibi Prabakaran)
Original Redmine Issue: 7073
Affected QGIS version: master
Redmine category:processing/qgis
Assignee: Sibi Prabakaran

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Platform Used: Ubuntu Linux 32-bit

The Intersection tool when performed on the same layer produces two intersection points overlapping each other.

Their attribute table data for the intersected points is something like this:
1,2
2,1

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• doIntersectLines.diff (Daniel Vaz)

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Related issue(s): #16115 (relates)
Redmine related issue(s): 7021

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[qgib]

Author Name: Sibi Prabakaran (Sibi Prabakaran)

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Pull Request submitted in #414

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• done_ratio was changed from 0 to 100

[qgib]

Author Name: Matthias Kuhn (@m-kuhn)

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Is this bugreport still valid after #16115 has been fixed?

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• status_id was changed from Open to Feedback

[qgib]

Author Name: Giovanni Manghi (@gioman)

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Matthias Kuhn wrote:

Is this bugreport still valid after #16115 has been fixed?

yes, because the result layer is empty.

Moreover if the tool is run using two different shapes I get

Traceback (most recent call last):
File "C:\OSGeo4W\apps\qgis-dev\python\plugins\fTools\tools\doIntersectLines.py", line 96, in accept
self.compute(line1, line2, field1, field2, outPath, self.progressBar)
File "C:\OSGeo4W\apps\qgis-dev\python\plugins\fTools\tools\doIntersectLines.py", line 169, in compute
outFeat.setAttribute(0, v1)
KeyError: '0'

I get the same error when running the tool using postgis layers.

[qgib]

Author Name: Daniel Vaz (Daniel Vaz)

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When lines are in the same layer, I think that there is a problem using the same provider to iterate over both lines. There is a strange behaviour, I don't know why, but it looks like that code:

provider2.select(allAttrs)

overriden the provider1, so in the loop:

while provider1.nextFeature(inFeat):

the attribute map of each feature (inFeat.attributeMap()) is an empty dict.

The patch attached includes the patch proposed by Sibi and adds a HACK that solves the problem, but it's not the correct way, I think.

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• 5952 was configured as doIntersectLines.diff

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• doIntersectLines.diff (Daniel Vaz)

[qgib]

Author Name: Daniel Vaz (Daniel Vaz)

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The hack that solves the problem, is added the following two lines before the while loop.

allAttrs = provider1.attributeIndexes()
provider1.select(allAttrs)
while provider1.nextFeature(inFeat):

[qgib]

Author Name: Daniel Vaz (Daniel Vaz)

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See pull request 702. #702

[qgib]

Author Name: Nathan Woodrow (@NathanW2)

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Fixed in changeset "56210eb0b5c7914d246b1c82ad48e676b00b6557".

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• status_id was changed from Feedback to Closed

[qgib]

Author Name: Giovanni Manghi (@gioman)

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The "ftools" category is being removed from the tracker, changing the category of this ticket to "Processing/QGIS" to not leave the category orphaned.