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7c8177e01a
Makes SelectByAttribute orders of magnitude faster for providers which support compiled expressions (eg Postgres), also allows algorithm to take advantage of database indexes created on attribute. For a 4 million point PostGIS layer (with an index on attribute) BEFORE: cancelled after 20 mins AFTER: ~2 seconds
127 lines
5.2 KiB
Python
127 lines
5.2 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 PyQt4.QtCore import QVariant
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from qgis.core import QgsExpression, QgsFeatureRequest
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from processing.core.GeoAlgorithm import GeoAlgorithm
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from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
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from processing.core.parameters import ParameterVector
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from processing.core.parameters import ParameterTableField
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from processing.core.parameters import ParameterSelection
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from processing.core.parameters import ParameterString
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from processing.core.outputs import OutputVector
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from processing.tools import dataobjects, vector
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class SelectByAttribute(GeoAlgorithm):
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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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]
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def defineCharacteristics(self):
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self.name, self.i18n_name = self.trAlgorithm('Select by attribute')
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self.group, self.i18n_group = self.trAlgorithm('Vector selection tools')
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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.addParameter(ParameterVector(self.INPUT,
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self.tr('Input Layer'), [ParameterVector.VECTOR_TYPE_ANY]))
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self.addParameter(ParameterTableField(self.FIELD,
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self.tr('Selection attribute'), self.INPUT))
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self.addParameter(ParameterSelection(self.OPERATOR,
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self.tr('Operator'), self.i18n_operators))
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self.addParameter(ParameterString(self.VALUE, self.tr('Value')))
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self.addOutput(OutputVector(self.OUTPUT, self.tr('Selected (attribute)'), True))
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def processAlgorithm(self, progress):
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fileName = self.getParameterValue(self.INPUT)
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layer = dataobjects.getObjectFromUri(fileName)
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fieldName = self.getParameterValue(self.FIELD)
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operator = self.OPERATORS[self.getParameterValue(self.OPERATOR)]
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value = self.getParameterValue(self.VALUE)
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fields = layer.pendingFields()
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idx = layer.fieldNameIndex(fieldName)
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fieldType = fields[idx].type()
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if fieldType != QVariant.String and operator in self.OPERATORS[-2:]:
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op = ''.join(['"%s", ' % o for o in self.OPERATORS[-2:]])
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raise GeoAlgorithmExecutionException(
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self.tr('Operators %s can be used only with string fields.' % op))
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if fieldType in [QVariant.Int, QVariant.Double]:
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progress.setInfo(self.tr('Numeric field'))
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expr = '"%s" %s %s' % (fieldName, operator, value)
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progress.setInfo(expr)
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elif fieldType == QVariant.String:
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progress.setInfo(self.tr('String field'))
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if operator not in self.OPERATORS[-2:]:
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expr = """"%s" %s '%s'""" % (fieldName, operator, value)
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elif operator == 'begins with':
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expr = """"%s" LIKE '%s%%'""" % (fieldName, value)
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elif operator == 'contains':
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expr = """"%s" LIKE '%%%s%%'""" % (fieldName, value)
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progress.setInfo(expr)
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elif fieldType in [QVariant.Date, QVariant.DateTime]:
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progress.setInfo(self.tr('Date field'))
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expr = """"%s" %s '%s'""" % (fieldName, operator, value)
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progress.setInfo(expr)
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else:
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raise GeoAlgorithmExecutionException(
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self.tr('Unsupported field type "%s"' % fields[idx].typeName()))
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qExp = QgsExpression(expr)
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if not qExp.hasParserError():
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qReq = QgsFeatureRequest(qExp)
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else:
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raise GeoAlgorithmExecutionException(qExp.parserErrorString())
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selected = [f.id() for f in layer.getFeatures(qReq)]
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layer.setSelectedFeatures(selected)
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self.setOutputValue(self.OUTPUT, fileName)
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