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Since it's safe to evaluate parameters in background threads now, it's usually going to be ok to evaluate everything in the processAlgorithm step. This keeps the algorithm code as simple as possible, and will make porting faster. Note that the prepare/postProcess virtual methods still exist and can be used when an algorithm MUST do setup/cleanup work in the main thread.
80 lines
3.3 KiB
Python
80 lines
3.3 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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CreateAttributeIndex.py
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-----------------------
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Date : November 2016
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Copyright : (C) 2016 by Nyall Dawson
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Email : nyall dot dawson at gmail dot com
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***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************
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"""
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__author__ = 'Nyall Dawson'
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__date__ = 'November 2016'
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__copyright__ = '(C) 2016, Nyall Dawson'
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# This will get replaced with a git SHA1 when you do a git archive
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__revision__ = '$Format:%H$'
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from qgis.core import (QgsVectorDataProvider,
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QgsFields,
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QgsApplication,
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QgsProcessingParameterVectorLayer,
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QgsProcessingParameterField,
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QgsProcessingParameterDefinition,
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QgsProcessingOutputVectorLayer)
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from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
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class CreateAttributeIndex(QgisAlgorithm):
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INPUT = 'INPUT'
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FIELD = 'FIELD'
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OUTPUT = 'OUTPUT'
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def group(self):
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return self.tr('Vector general tools')
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def __init__(self):
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super().__init__()
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self.addParameter(QgsProcessingParameterVectorLayer(self.INPUT,
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self.tr('Input Layer')))
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self.addParameter(QgsProcessingParameterField(self.FIELD,
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self.tr('Attribute to index'), None, self.INPUT))
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self.addOutput(QgsProcessingOutputVectorLayer(self.OUTPUT, self.tr('Indexed layer')))
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def name(self):
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return 'createattributeindex'
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def displayName(self):
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return self.tr('Create attribute index')
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def processAlgorithm(self, parameters, context, feedback):
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layer = self.parameterAsVectorLayer(parameters, self.INPUT, context)
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field = self.parameterAsString(parameters, self.FIELD, context)
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provider = layer.dataProvider()
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field_index = layer.fields().lookupField(field)
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if field_index < 0 or layer.fields().fieldOrigin(field_index) != QgsFields.OriginProvider:
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feedback.pushInfo(self.tr('Can not create attribute index on "{}"').format(field))
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else:
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provider_index = layer.fields().fieldOriginIndex(field_index)
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if provider.capabilities() & QgsVectorDataProvider.CreateAttributeIndex:
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if not provider.createAttributeIndex(provider_index):
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feedback.pushInfo(self.tr('Could not create attribute index'))
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else:
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feedback.pushInfo(self.tr("Layer's data provider does not support "
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"creating attribute indexes"))
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return {self.OUTPUT: layer.id()}
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