Bug report #962

Postgis table with float type attribute interprets null as zero.

Added by cgsbob - over 16 years ago. Updated over 16 years ago.

Status:Closed
Priority:Low
Assignee:Jürgen Fischer
Category:Vectors
Affected QGIS version: Regression?:No
Operating System:Debian Easy fix?:No
Pull Request or Patch supplied: Resolution:fixed
Crashes QGIS or corrupts data: Copied to github as #:11021

Description

I tried to use Symbology>Continuous Color on a field that has nulls and noticed that these null values are interpreted as 0. As a result, I am getting a lot of black dots on my map (which I hoped would not show up on my map) along with white to red colored dots.

I also notice that "Open attribute table" shows these fields as 0 instead of null.

nullprob.png - This illustrates Continuous Color (and other) rendering problems with nulls (170 KB) cgsbob -, 2008-02-28 11:36 AM

nulls_appear.png - shades of red is from continuous color render. black feature has null attribute. (51.8 KB) cgsbob -, 2008-03-26 09:38 PM

zoom_lower_right.png - zoom into lower right of maps...red features disappear (12 KB) cgsbob -, 2008-03-26 09:40 PM

gw_elev.pgdmp - postgresql dump of the problem feature (33.8 KB) cgsbob -, 2008-03-28 08:52 AM

Associated revisions

Revision de07d465
Added by Jürgen Fischer over 16 years ago

fix #962: the image of the previously rendered feature was used instead of an empty one.

git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@8294 c8812cc2-4d05-0410-92ff-de0c093fc19c

Revision 90e8d1eb
Added by Jürgen Fischer over 16 years ago

fix #962: the image of the previously rendered feature was used instead of an empty one.

git-svn-id: http://svn.osgeo.org/qgis/trunk@8294 c8812cc2-4d05-0410-92ff-de0c093fc19c

History

#1 Updated by Frank Warmerdam - over 16 years ago

I chatted about this very briefly on IRC and Bob reasonable suggested that the attribute table ought to show the field as NULL (perhaps blank) and the rendering might just not draw features with null fields for classification.

I skimmed the OGR provider and I see it makes no effort to distingish between NULL and non-null fields. Is it intended that providers can return features with NULL attributes marked in some fashion in the attribute map? Perhaps, those attributes should just not be added to the attribute map for that feature?

Skimming the Postgres provider, it also seems to make no effort to distingish between null and non-null field values.

Perhaps the problem is just at the provider level?

#2 Updated by cgsbob - over 16 years ago

Replying to cgsbob:
The image I just uploaded has a bug :-) The beginning arrow coming from the pgadmin3 window should begin at record 141 (one cell below).

#3 Updated by cgsbob - over 16 years ago

Replying to [comment:2 cgsbob]:

Replying to cgsbob:
The image I just uploaded has a bug :-) The beginning arrow coming from the pgadmin3 window should begin at record 141 (one cell below).

Disregard this the comment above...it is correct. Is there a way to delete comments?

#4 Updated by Jürgen Fischer over 16 years ago

  • Status changed from Open to Closed
  • Resolution set to fixed

#5 Updated by cgsbob - over 16 years ago

Replying to [comment:5 jef]:
I see that the attribute table now shows nulls as NULL, but the feature is still rendered as black dots. I was hoping that fixing #962 meant that the null attributes would not be rendered.

#6 Updated by Jürgen Fischer over 16 years ago

  • Status changed from Closed to Feedback
  • Resolution deleted (fixed)

#7 Updated by Jürgen Fischer over 16 years ago

  • Status changed from Feedback to Closed
  • Resolution set to fixed

fixed in

#8 Updated by cgsbob - over 16 years ago

Replying to [comment:8 jef]:

fixed in

I wish this was an easier bug to fix, but there is still a problem :-) The null point features the color range white to red). When you zoom in these null point features disappears.

#9 Updated by Jürgen Fischer over 16 years ago

  • Resolution deleted (fixed)
  • Status changed from Closed to Feedback

Replying to [comment:9 cgsbob]:

Replying to [comment:8 jef]:

fixed in

I wish this was an easier bug to fix, but there is still a problem :-) The null point features the color range white to red). When you zoom in these null point features disappears.

Sorry, I don't get what you're saying. Did you post get mixed up?

#10 Updated by cgsbob - over 16 years ago

Replying to [comment:10 jef]:

Replying to [comment:9 cgsbob]:

Replying to [comment:8 jef]:

fixed in

I wish this was an easier bug to fix, but there is still a problem :-) The null point features the color range white to red). When you zoom in these null point features disappears.

Sorry, I don't get what you're saying. Did you post get mixed up?

Yes, I did mix up my post. I was trying to say that the features that have null attribute still appear in my map and when I zoom in those features they disappear. I'll upload some pics to demonstrate.

#11 Updated by Jürgen Fischer over 16 years ago

  • Status changed from Feedback to Closed
  • Resolution set to fixed

You probably missed the working version. might have worked, but my optimization in 9a584ede (SVN r8287) actually broke the postgres provider. I think I've fixed that in fa696cda (SVN r8291).

#12 Updated by Jürgen Fischer over 16 years ago

  • Resolution deleted (fixed)
  • Status changed from Closed to Feedback

#13 Updated by Jürgen Fischer over 16 years ago

  • Status changed from Feedback to Closed
  • Resolution set to fixed

thanks for the patience. I think I finally got it right.

#14 Updated by cgsbob - over 16 years ago

Replying to [comment:14 jef]:

thanks for the patience. I think I finally got it right.

I just updated from svn. Everything (well, almost everything :) ) is all right. One little cosmetic change you can make is to update the extent.

Thanks for all your work!

#15 Updated by Jürgen Fischer over 16 years ago

Replying to [comment:15 cgsbob]:

One little cosmetic change you can make is to update the extent.

I don't think the is a rendering issue. If you don't want to handle the null features at all, I'd suggest that you filter them out using a where clause.

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