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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.
139 lines
5.5 KiB
Python
139 lines
5.5 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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SelectByAttribute.py
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---------------------
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Date : May 2010
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Copyright : (C) 2010 by Michael Minn
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Email : pyqgis at michaelminn 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__ = 'Michael Minn'
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__date__ = 'May 2010'
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__copyright__ = '(C) 2010, Michael Minn'
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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 (QgsApplication)
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from qgis.PyQt.QtCore import QVariant
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from qgis.core import (QgsExpression,
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QgsProcessingUtils,
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QgsProcessingParameterVectorLayer,
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QgsProcessingParameterField,
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QgsProcessingParameterEnum,
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QgsProcessingParameterString,
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QgsProcessingOutputVectorLayer)
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from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
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from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
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class SelectByAttribute(QgisAlgorithm):
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INPUT = 'INPUT'
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FIELD = 'FIELD'
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OPERATOR = 'OPERATOR'
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VALUE = 'VALUE'
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OUTPUT = 'OUTPUT'
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OPERATORS = ['=',
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'!=',
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'>',
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'>=',
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'<',
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'<=',
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'begins with',
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'contains',
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'is null',
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'is not null',
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'does not contain'
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]
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STRING_OPERATORS = ['begins with',
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'contains',
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'does not contain']
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def tags(self):
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return self.tr('select,attribute,value,contains,null,field').split(',')
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def group(self):
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return self.tr('Vector selection tools')
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def __init__(self):
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super().__init__()
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self.i18n_operators = ['=',
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'!=',
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'>',
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'>=',
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'<',
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'<=',
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self.tr('begins with'),
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self.tr('contains'),
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self.tr('is null'),
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self.tr('is not null'),
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self.tr('does not contain')
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]
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self.addParameter(QgsProcessingParameterVectorLayer(self.INPUT, self.tr('Input layer')))
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self.addParameter(QgsProcessingParameterField(self.FIELD,
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self.tr('Selection attribute'), parentLayerParameterName=self.INPUT))
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self.addParameter(QgsProcessingParameterEnum(self.OPERATOR,
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self.tr('Operator'), self.i18n_operators))
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self.addParameter(QgsProcessingParameterString(self.VALUE, self.tr('Value')))
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self.addOutput(QgsProcessingOutputVectorLayer(self.OUTPUT, self.tr('Selected (attribute)')))
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def name(self):
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return 'selectbyattribute'
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def displayName(self):
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return self.tr('Select by attribute')
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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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fieldName = self.parameterAsString(parameters, self.FIELD, context)
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operator = self.OPERATORS[self.parameterAsEnum(parameters, self.OPERATOR, context)]
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value = self.parameterAsString(parameters, self.VALUE, context)
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fields = layer.fields()
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idx = layer.fields().lookupField(fieldName)
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fieldType = fields[idx].type()
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if fieldType != QVariant.String and operator in self.STRING_OPERATORS:
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op = ''.join(['"%s", ' % o for o in self.STRING_OPERATORS])
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raise GeoAlgorithmExecutionException(
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self.tr('Operators {0} can be used only with string fields.').format(op))
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field_ref = QgsExpression.quotedColumnRef(fieldName)
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quoted_val = QgsExpression.quotedValue(value)
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if operator == 'is null':
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expression_string = '{} IS NULL'.format(field_ref)
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elif operator == 'is not null':
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expression_string = '{} IS NOT NULL'.format(field_ref)
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elif operator == 'begins with':
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expression_string = """%s LIKE '%s%%'""" % (field_ref, value)
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elif operator == 'contains':
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expression_string = """%s LIKE '%%%s%%'""" % (field_ref, value)
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elif operator == 'does not contain':
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expression_string = """%s NOT LIKE '%%%s%%'""" % (field_ref, value)
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else:
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expression_string = '{} {} {}'.format(field_ref, operator, quoted_val)
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expression = QgsExpression(expression_string)
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if expression.hasParserError():
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raise GeoAlgorithmExecutionException(expression.parserErrorString())
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layer.selectByExpression(expression_string)
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return {self.OUTPUT: parameters[self.INPUT]}
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