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I have a shapefile containing cadastral data. I would like to dissolve the polygons using my field "OwnerName". My goal is to get one polygon per landlord's name.

When I use the "Dissolve" tool, QGIS creates an empty output layer (but with the right column titles, see the screenshot attached).

First I thought that maybe I could not dissolve some polygons using a field containing some text (my "OwnerName" field), so I created a field containing a decimal number ID for each owner name. I tried to dissolve the polygons again. Same result : an empty layer. The reason may be the size of the attribute table. I have 65,500 polygons.

Any idea?

Thanks enter image description here (QGIS 1.8.0 Lisboa - Windows 7)

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  • can you display the results i.e screenshoot of the dissolved output?
    – Arun
    Commented Sep 13, 2013 at 3:52
  • I have attached a screenshot of the empty attribute table of the dissolved output. Thanks
    – Bap
    Commented Sep 13, 2013 at 18:42
  • What happens if you try "dissolve all" options, regardless of the attribute value?
    – Michal Zimmermann
    Commented Sep 14, 2013 at 6:28
  • When I "dissolve all" the tool stops around 60% of completion. I tried a few times with the same result.
    – Bap
    Commented Sep 25, 2013 at 17:31

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The problem was the size of the shapefile. I ran the Dissolve tool over the week-end and it worked. It took 40 hours to complete the process. The first 1% shows up after 45 mins. I was not patient enough and though it was not working while actually I should have waited longer. Thanks

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    Consider using postgis or sqlite for speeding up things. Look for instance for st_unaryunion
    – Curlew
    Commented Oct 2, 2013 at 16:57

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