Bug report #19441

Layers with 80+ rule-based symbology do not render

Added by Basil Eric Rabi over 6 years ago. Updated over 6 years ago.

Status:Closed
Priority:Normal
Assignee:Alessandro Pasotti
Category:Symbology
Affected QGIS version:3.3(master) Regression?:No
Operating System: Easy fix?:No
Pull Request or Patch supplied:Yes Resolution:fixed/implemented
Crashes QGIS or corrupts data:No Copied to github as #:27269

Description

When a layer has less than 81 rule-based symbology, it renders without issues.
When a layer has reached more than 80 rule-based symbology, the layer is not rendered in the canvas.

This is tested in both master (fedora 28) and 3.2.0 (windows).

DH.qgz - Project file (18.4 KB) Basil Eric Rabi, 2018-07-18 08:33 AM

sample.gpkg - Sample data (1.22 MB) Basil Eric Rabi, 2018-07-18 08:33 AM

Associated revisions

Revision 3ea67af6
Added by Alessandro Pasotti over 6 years ago

[bugfix] Create a b-tree expr when rule based renderer has more than 50 rules

Fixes #19441 Layers with 80+ rule-based symbology do not render

History

#1 Updated by Giovanni Manghi over 6 years ago

  • Category changed from GUI to Symbology

#2 Updated by Giovanni Manghi over 6 years ago

  • Status changed from Open to Feedback

Did it works as expected on 2.18?

#3 Updated by Basil Eric Rabi over 6 years ago

  • Status changed from Feedback to Open

In 2.18, layer is not rendered when the rules are 82 and above.

#4 Updated by Igor Evdokimov over 6 years ago

I have layer with +4000 rule-based symbology. (Need this to make selection with line hatch).
QGis 3.2 terminates without any message and any dump starting at 800-900 rules. Windows7 x64.
When layer has less rules - all works fine.

#5 Updated by Alessandro Pasotti over 6 years ago

  • Assignee set to Alessandro Pasotti

#6 Updated by Alessandro Pasotti over 6 years ago

Doing some progresses here, (with some help from Even) we've identified the source of the issue which is in sqlite library limits.

See https://github.com/oniony/TMSU/wiki/Troubleshooting for the error "parser stack overflow" (bison related)

There is another error when the tree depth is too high: "Expression tree is too large (maximum depth 1000)" according to https://www.sqlite.org/limits.html, "The maximum number of bytes in the text of an SQL statement is limited to SQLITE_MAX_SQL_LENGTH which defaults to 1000000"

Unfortunately the solution doesn't seem to be trivial.

#7 Updated by Alessandro Pasotti over 6 years ago

  • Status changed from Open to In Progress
  • Pull Request or Patch supplied changed from No to Yes

#8 Updated by Basil Eric Rabi over 6 years ago

Just tested the patch. It works great! Thank you.

#9 Updated by Anonymous over 6 years ago

  • Status changed from In Progress to Closed
  • % Done changed from 0 to 100

#10 Updated by Giovanni Manghi over 6 years ago

  • Resolution set to fixed/implemented

#11 Updated by Igor Evdokimov over 6 years ago

Tested the patch also. It works now, but not great for my task. Very slow.
I have >4000 categories. With category-based symbology all works fine.

But we need to make hatched selection of polygons. Even standard hatches/line pattern
(diagonal, cross, etc.) will be enough, but not simple "color fill", as it is now in QGis.
So I had to implement this with rule-based symbology using <is_selected()> function
on map features. With this workaround on ~60 rules all works fine also, but on 4000 - very slow.

So I think I have to write feature request to make full-featured instrument
of "selection pattern" tuning (as it is in style editor, for example).

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