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I am new to QGIS and I am currently learning pyqgis. My problem is I tried to create a custom plugin to join csv and shapefile with 20,000+ features. I was successful in joining csv and shapefile via custom plugin that I created using this code.

from PyQt4.QtCore import *
import qgis
from qgis.core import QgsMapLayerRegistry, QgsVectorJoinInfo

for layer in QgsMapLayerRegistry.instance().mapLayers().values():
    # Change to your shapefile name
    if layer.name() == "MyShapefile":
        qgis.utils.iface.setActiveLayer(layer)
        shp = qgis.utils.iface.activeLayer()

for layer in QgsMapLayerRegistry.instance().mapLayers().values():
    # Change to your csv name
    if layer.name() == "MyDatabase":
        qgis.utils.iface.setActiveLayer(layer)
        csv = qgis.utils.iface.activeLayer()

# Set up join parameters
shpField='PIN'
csvField='UPIN'
joinObject = QgsVectorJoinInfo()
joinObject.joinLayerId = csv.id()
joinObject.joinFieldName = csvField
joinObject.targetFieldName = shpField
shp.addJoin(joinObject)

But when i try to open the attribute table it loads very slow and counting features by 8/10/15 at max. But when I join table using properties>join of shapefile and check the "cache data in virtual memory" my attributes loads perfectly fine even if I have 20,000 features.

My question is how can I make the loading of attribute table faster like in joining via properties>join using a custom plugin?

I am using QGIS 2.16

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1 Answer 1

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Try adding joinObject.memoryCache = True before you initiate the join:

from PyQt4.QtCore import *
import qgis
from qgis.core import QgsMapLayerRegistry, QgsVectorJoinInfo

shp = QgsMapLayerRegistry.instance().mapLayersByName( "MyShapefile" )[0]
csv = QgsMapLayerRegistry.instance().mapLayersByName( "MyDatabase" )[0]

# Set up join parameters
shpField='PIN'
csvField='UPIN'
joinObject = QgsVectorJoinInfo()
joinObject.joinLayerId = csv.id()
joinObject.joinFieldName = csvField
joinObject.targetFieldName = shpField
joinObject.memoryCache = True
shp.addJoin(joinObject)
# shp.createJoinCaches()
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  • will try it now sir Jospeh. Thank you for replying. Godbless you. :)
    – Conrado Domingo
    Commented Sep 28, 2016 at 4:04
  • Hi Sir Joseph, I tried adding joinObject.memoryCache = True but still with no luck.. the attribute table still loads very slow counting by 8/10/15. I tried using it thru Macro and my Custom Join Plugin. Thank you and more power.
    – Conrado Domingo
    Commented Sep 28, 2016 at 4:25
  • No need to thank me for replying =). Does it work if you do it in the Python Console?
    – Joseph
    Commented Sep 28, 2016 at 8:44
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    It takes a few seconds thanks to the memory cache. I asked a somewhat related question here where my layers did not load both visually and the attribute table. The code was used in a plugin. I wonder why it is still slow for you...I also simplified your code a bit =)
    – Joseph
    Commented Sep 29, 2016 at 10:15
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    well i think I figured it out.. as you can see in my script UPIN is in all caps while in my csv it should be small letters upin i changed it in the code and now it loads in an instant. :) Thank you for the support! :) hope to hear from you soon!
    – Conrado Domingo
    Commented Sep 29, 2016 at 11:31

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